[
{
"id": "authors:pza4w-9v637",
"collection": "authors",
"collection_id": "pza4w-9v637",
"cite_using_url": "https://authors.library.caltech.edu/records/pza4w-9v637",
"type": "article",
"title": "Non-ideal MHD and protostellar feedback effects on disk formation and evolution in numerical simulations of star cluster formation",
"author": [
{
"family_name": "Filippova",
"given_name": "Nina",
"orcid": "0000-0002-8027-0216"
},
{
"family_name": "Offner",
"given_name": "Stella S R",
"orcid": "0000-0003-1252-9916"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "While recent surveys have resolved hundreds of nearby protostellar disks, numerical simulations assuming ideal magnetohydrodynamics (MHD) have historically struggled to achieve disk formation due to efficient angular momentum removal by magnetic torques. Non-ideal MHD effects, relevant at the low ionization fractions typical of molecular clouds, have been shown to reduce the effectiveness of magnetic braking and promote disk formation. In this work, we present the results from a suite of calculations following the gravitational collapse of 50 M\u2299 turbulent molecular cloud cores down to the formation and evolution of stellar systems and protostellar disks. We use the radiation-MHD code gizmo including non-ideal MHD (Ohmic resistivity, ambipolar diffusion, and the Hall effect) and the starforge numerical framework for modeling star formation and stellar feedback. We compare the effects of assuming ideal vs. non-ideal MHD and including sub-grid protostellar jet feedback on disk formation and evolution. Disks form in all of our models but are least massive in the model with ideal MHD and sub-grid jet feedback. Apart from the ideal MHD+jets model, we do not observe any significant differences in disk properties between the ideal and non-ideal MHD models; however, ideal MHD disks are embedded in smaller rotating envelopes. Disk sizes are in general agreement with those of observed disks. Jet feedback increases core fragmentation and reduces final stellar masses. Our results suggest that magnetic braking does not efficiently suppress disk formation, regardless of whether ideal or non-ideal MHD is assumed, under the dynamical conditions in which multiple stellar systems form.
",
"doi": "10.1093/mnras/stag1501",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2026-09",
"series_number": "2",
"volume": "551",
"issue": "2",
"pages": "stag1501"
},
{
"id": "authors:qbhs6-vre08",
"collection": "authors",
"collection_id": "qbhs6-vre08",
"cite_using_url": "https://authors.library.caltech.edu/records/qbhs6-vre08",
"type": "article",
"title": "Residual energy in weakly compressible turbulence with a mean guide field",
"author": [
{
"family_name": "Skalidis",
"given_name": "Raphael",
"orcid": "0000-0003-2337-0277",
"clpid": "Skalidis-Rafail"
},
{
"family_name": "Tritsis",
"given_name": "Aris",
"orcid": "0000-0003-4987-7754"
},
{
"family_name": "Beattie",
"given_name": "James R.",
"orcid": "0000-0001-9199-7771"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Context. Energy distribution is a fundamental property of magnetohydrodynamic (MHD) turbulence. In strongly magnetized turbulence, energy imbalances can arise, which can be quantified by the so-called residual energy: Er = (Ekin − Emag). Here, Ekin and Emag stand for the volume-averaged kinetic and magnetic energy, respectively. Numerical simulations of incompressible turbulence yield Er < 0, which is consistent with solar wind observations; whereas in highly compressible turbulence simulations, we have Er > 0. Differences arise in the cascade of Er between the two regimes.
\nAims. We explore the properties of Er in weakly compressible MHD turbulence in the presence of an initially strong (guide) magnetic field. We study the influence of different driving mechanisms and field strengths on the cascade of Er.
\nMethods. We ran a suite of direct numerical simulations with the PENCIL code. All simulations were maintained through forcing in a quasi-static regime with sonic Mach numbers close to 0.1 for a number of different crossing times. We solely changed the Alfvén Mach number or, equivalently, the plasma beta (β) of the simulations. We drove turbulence by either injecting velocity or magnetic fluctuations at large scales and we studied the power spectra of kinetic, magnetic, density, and Er.
\nResults. Magnetically driven simulations show dominant Alfvénic fluctuations and a ∝k−3/2 scaling in all spectra. In the inertial range Er ≈ 0. Turbulence is balanced with zero net cross-helicity, but exhibit strong locally imbalanced fluctuations that are qualitatively consistent with the dynamic alignment theory. Kinetically driven simulations give rise to a ∝k−1 scaling, consistent with weakly interacting modes that preserve a high level of coherence throughout the inertial range. For the kinetically driven simulations, we report an excess in kinetic energy with respect to magnetic at all scales of the inertial range. The cascade of the residual energy (Er ∝ kα) depends on β and scales as: for β = 4.0, −2 \u2272 α \u2272 −5/3, for β = 1.0, −5/3 \u2272 α \u2272 −3/2, and for β = 0.3, α ≈ −1.
\nConclusions. The energy partition in weakly compressible turbulence is strongly influenced by the forcing mechanism, even when the global sonic and Alfvénic Mach numbers are comparable across simulations.
",
"doi": "10.1051/0004-6361/202558554",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy & Astrophysics",
"publication_date": "2026-09",
"volume": "713",
"pages": "A7"
},
{
"id": "authors:ezdcn-xwc86",
"collection": "authors",
"collection_id": "ezdcn-xwc86",
"cite_using_url": "https://authors.library.caltech.edu/records/ezdcn-xwc86",
"type": "article",
"title": "Direct Tests of Black Hole Accretion Rate Prescriptions. I. Bondi Accretion at Different Scales",
"author": [
{
"family_name": "Agostino",
"given_name": "James",
"orcid": "0000-0002-8122-3032"
},
{
"family_name": "Lin",
"given_name": "Ming-Yi",
"orcid": "0000-0002-5031-4898"
},
{
"family_name": "Jones",
"given_name": "Natasha"
},
{
"family_name": "Medling",
"given_name": "Anne M.",
"orcid": "0000-0001-7421-2944"
},
{
"family_name": "Barcos-Mu\u00f1oz",
"given_name": "Loreto",
"orcid": "0000-0003-0057-8892"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945"
},
{
"family_name": "Ricci",
"given_name": "Claudio",
"orcid": "0000-0001-5231-2645"
},
{
"family_name": "Privon",
"given_name": "George C.",
"orcid": "0000-0003-3474-1125"
},
{
"family_name": "U",
"given_name": "Vivian",
"orcid": "0000-0002-1912-0024",
"clpid": "U-Vivian"
},
{
"family_name": "Torrey",
"given_name": "Paul",
"orcid": "0000-0002-5653-0786"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Max",
"given_name": "Claire",
"orcid": "0000-0003-0682-5436"
}
],
"abstract": "We present spatially resolved parsec-scale measurements of nuclear conditions (gas density and kinetic temperature) relevant for black hole accretion rate predictions in the Seyfert 2 galaxy, NGC 1068. We inject these parameters into the prescription for a Bondi-like accretion model, then compare the resulting accretion rate prediction to the empirical accretion rate derived from hard X-ray observations. Cosmological simulations have spatial resolution ranging from ∼10 pc to approximately kiloparsec scales, and so for reasonable comparison we test these accretion rate predictions in pixel-sized radial steps out to 500 pc. Compared to warm H2 gas, CO gas is the dominant mass carrier close to the SMBH. We find that the Bondi accretion rate (M \u0307 Bondi) of cold molecular gas alone (measured using CO) overestimates the true accretion rate by up to 14 dex in a small aperture (r \u22725 pc) around the black hole, and by at least 8 dex inside large apertures (r \u2272500 pc). These results are the first in a series of direct tests of accretion rate prescriptions, and they suggest that using a Bondi accretion formalism to model supermassive black hole accretion in Seyfert 2 galaxies may lead to overestimated accretion rates in simulations.
",
"doi": "10.3847/1538-4357/ae80ca",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2026-08-10",
"series_number": "1",
"volume": "1007",
"issue": "1",
"pages": "23"
},
{
"id": "authors:xbgzr-reh76",
"collection": "authors",
"collection_id": "xbgzr-reh76",
"cite_using_url": "https://authors.library.caltech.edu/records/xbgzr-reh76",
"type": "article",
"title": "A Hot DOG Forged in FIRE: Nuclear and Starburst Spectral Decomposition of a Luminous Infrared Galaxy Simulation with a Resolved Dust Torus",
"author": [
{
"family_name": "Bardati",
"given_name": "Jaeden",
"orcid": "0009-0002-8417-4480",
"clpid": "Bardati-Jaeden"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628"
}
],
"abstract": "\n
Ultraluminous infrared galaxies are powered by a combination of rapid star formation and active galactic nucleus (AGN) emission, but their relative importance is not always observationally clear. We study the galactic continuum spectrum of a cosmologically simulated ∼4 × 1010M\u2299 stellar mass starburst galaxy at redshift z ∼ 4.4 that refines down to resolve beyond the dust sublimation boundary of its super-Eddington-accreting ∼107M\u2299 supermassive black hole. We find that this system resembles the rare class of hot dust-obscured galaxy (Hot DOG), with a roughly flat (in νFν) IR emission spectrum that sharply drops off at wavelengths \u22725 μm. Our system also matches with the observational properties of many Hot DOGs, including undergoing multiple galaxy mergers and being the most massive galaxy within a dense cosmological environment. The distinctive Hot DOG spectral shape in our system is caused by AGN-heated mid-IR warm dust, predominately starburst-heated far-IR cold dust, and a steep near- to mid-IR cutoff caused by strong absorption in the dense ISM of the galactic nucleus, rather than the dust torus itself. This system is lower luminosity (LIR ∼ 2 × 1012L\u2299) than those detected by the WISE survey at similar redshifts, but will be a prime target for future far-IR surveys such as PRIMA. Our results show that Hot DOGs can naturally result as a transitional phase during rapid AGN accretion, but before significant AGN-driven outflows clear optically thin paths.
\n
We investigate how galactic disk structures connect to the detailed properties of their host dark-matter halos using the TNG50 simulation. From the hydrodynamic and matched dark-matter-only runs, we measure a comprehensive list of halo properties describing density structure, angular momentum, shape, assembly history, and environment. Using the morphological decomposition developed in Paper I, we quantify the sizes, scale heights, and mass fractions of the disk components for galaxies at 0 ≤ z ≤ 4. A random forest regression shows that halo properties alone predict disk size and thickness with high accuracy, while a symbolic regression (SR) provides compact empirical relations with slightly lower accuracy. Disk height is consistently easier to predict than disk size, and lower-mass halos yield higher accuracy than massive halos. Predictions based on halo properties measured in the hydro simulations outperform those based on halos matched in the dark-matter-only simulation, reflecting the imprint of baryonic restructuring on the inner halo. The SHAP analysis reveals the most informative halo parameters include concentration, Einasto shape, global and inner spin, and recent mass accretion, although their importance varies across disk properties. We show correlations between disk size and the density–profile shape arise primarily from a disk-induced modification of the inner halo, rather than a primordial connection. Finally, we point out that disks become more extended with respect to their host halos at higher redshift in low-mass halos, while massive high-redshift halos show the opposite trend. We provide SR-based prescriptions that accurately map halo properties to disk structures, offering practical tools for galaxy–halo modeling.
",
"doi": "10.3847/1538-4357/ae5821",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2026-05-20",
"series_number": "1",
"volume": "1003",
"issue": "1",
"pages": "12"
},
{
"id": "authors:7qhcn-mkx32",
"collection": "authors",
"collection_id": "7qhcn-mkx32",
"cite_using_url": "https://authors.library.caltech.edu/records/7qhcn-mkx32",
"type": "article",
"title": "Galaxy Metallicity Gradients in the Epoch of Reionization from the FIRE-2 Simulations",
"author": [
{
"family_name": "Sun",
"given_name": "Xunda",
"orcid": "0009-0005-8170-5153"
},
{
"family_name": "Wang",
"given_name": "Xin",
"orcid": "0000-0002-9373-3865"
},
{
"family_name": "Jiang",
"given_name": "Fangzhou",
"orcid": "0000-0001-6115-0633"
},
{
"family_name": "Mo",
"given_name": "Houjun",
"orcid": "0000-0001-5356-2419"
},
{
"family_name": "Ho",
"given_name": "Luis C.",
"orcid": "0000-0001-6947-5846"
},
{
"family_name": "Zhou",
"given_name": "Qianqiao"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349"
},
{
"family_name": "Zhan",
"given_name": "Hu",
"orcid": "0000-0003-1718-6481"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942"
},
{
"family_name": "Graf",
"given_name": "Russell L.",
"orcid": "0009-0009-8310-8992"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565"
}
],
"abstract": "\n
We employ the high-redshift suite of FIRE-2 cosmological hydrodynamic zoom-in simulations to investigate the evolution of gas-phase metallicity radial gradients in galaxies in the epoch of reionization (EOR). Our sample consists of 22 galaxies spanning the redshift range z ∼ 10–5. We find that galaxies at z ∼ 10 exhibit a median metallicity gradient of −0.15 dex kpc−1 with substantial scatter, which gradually flattens to −0.1 dex kpc−1 at z ∼ 6, accompanied by a reduction in scatter. In the EOR, metallicity gradients correlate positively with stellar mass: more massive galaxies display flatter gradients with smaller scatter, broadly consistent with recent JWST observations. At fixed stellar mass, galaxies with a higher star formation rate (SFR) exhibit steeper negative gradients, while the specific SFR shows a strong anticorrelation with gradient slope. Because EOR galaxies in FIRE-2 generally lack significant rotational support, we adopt the ratio of the peak-to-peak velocity shear to twice the velocity dispersion (Δv/2σ) as a proxy for the strength of gas flows. We find a strong positive correlation between metallicity gradients and Δv/2σ: galaxies with a lower Δv/2σ (i.e., weaker gas flows) tend to exhibit steeper negative gradients. Furthermore, galaxies with a steeper gradient display higher central SFR surface densities, suggesting localized star formation with inefficient interstellar medium mixing that drives inside-out chemical enrichment in galaxy evolution in the early Universe.
\n
\n
Cosmic rays (CRs) drive ionization and influence gas dynamics in molecular clouds (MCs), potentially impacting the resulting star formation outcomes. Although previous simulations of individual star formation have included methods for CR transport (CRT), none have been large enough to resolve the stellar initial mass function (IMF). We conduct numerical simulations following the collapse of a 20,000 M\u2299 MC and the subsequent star formation including CRT, both with and without CRs accelerated by winds from the young massive stars, and compare against a non-CRT simulation. We show that after the first massive stars form, the cavity produced by feedback is more pronounced in the CRT simulations because the external CRs are able to propagate inward and compress the gas into higher-density structures. This increases the subsequent star formation in the cloud; by the end of the simulation, the star formation efficiency (SFE) in the CRT simulation including stellar wind CRs is 43% higher than the non-CRT simulation. The IMF is also top-heavy in comparison, with a slope above 1 M\u2299 that is shallower by ∼20%. These effects are also present in the simulation without wind-accelerated CRs, but they are not as pronounced; the SFE is only 16% higher than the non-CRT simulation, and the IMF high-mass slope is shallower by ∼10%. These results may explain some of the observed top-heavy IMFs, which typically occur in high-CR environments such as the Galactic center.
\n
Multiple models have been suggested over the years to explain the structure and support of accretion disks around supermassive black holes—from the standard thin thermal-pressure-dominated \ud835\udefc-disk model to more recent models that describe geometrically thicker radiation or magnetic or turbulence-dominated disks. In any case, objects embedded in the disk (e.g. compact objects, stars, gas, dust) can undergo gravitational and hydrodynamic interactions with each other leading to interesting processes such as binary interaction/capture, gravitational wave merger events, dynamical friction, accretion, gap opening, etc. It has long been argued that disks of active galactic nuclei (AGN) can enhance the rates for many of these events; however, almost all of that analysis has assumed specific thin-disk models (with aspect ratios \ud835\udc3b\u2061/\ud835\udc45 \u22720.01). We show here that the rates for processes such as these that are mediated by gravitational cross sections has a very strong inverse dependence on the thickness \ud835\udc3b\u2061/\ud835\udc45 (scaling as steeply as (\ud835\udc3b\u2061/\ud835\udc45)\u207b\u2078), and \ud835\udc3b\u2061/\ud835\udc45 can vary in the outer disk (where these processes are often invoked) by factors \u22731000 depending on the assumed source of pressure support in the disk. This predicts rates that can be lower by tens of orders-of-magnitude in some models, demonstrating that it is critical to account for disk parameters such as aspect ratio and different sources of disk pressure when computing any meaningful predictions for these rates. For instance, if magnetic pressure is important in the outer disk, as suggested in recent work, capture rates would be suppressed by factors ∼10¹\u2070–10²\u2070 compared to previous studies where magnetic pressure was ignored.
",
"doi": "10.1103/gcwt-rmml",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2026-03-20",
"series_number": "6",
"volume": "113",
"issue": "6",
"pages": "063036"
},
{
"id": "authors:858fv-x3v13",
"collection": "authors",
"collection_id": "858fv-x3v13",
"cite_using_url": "https://authors.library.caltech.edu/records/858fv-x3v13",
"type": "article",
"title": "Confronting the Diversity Problem: The Limits of Galaxy Rotation Curves as a Tool to Understand Dark Matter Profiles",
"author": [
{
"family_name": "Sands",
"given_name": "Isabel S.",
"orcid": "0000-0002-1159-4882",
"clpid": "Sands-Isabel-S"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Shen",
"given_name": "Xuejian",
"orcid": "0000-0002-6196-823X"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X"
},
{
"family_name": "Bullock",
"given_name": "James",
"orcid": "0000-0003-4298-5082"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628"
},
{
"family_name": "Mercado",
"given_name": "Francisco J.",
"orcid": "0000-0002-5908-737X"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232"
},
{
"family_name": "Necib",
"given_name": "Lina",
"orcid": "0000-0003-2806-1414",
"clpid": "Necib-L"
},
{
"family_name": "Ou",
"given_name": "Xiaowei",
"orcid": "0000-0002-4669-9967"
},
{
"family_name": "Wellons",
"given_name": "Sarah"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942"
}
],
"abstract": "\n
While galaxy rotation curves (RCs) provide one of the most powerful methods for measuring dark matter profiles in the inner regions of rotation-supported galaxies, at the dwarf scale there are factors that can complicate this analysis. Given the expectation of a universal profile in dark-matter-only simulations, the diversity of the observed RCs has become an often-discussed issue in Lambda cold dark matter cosmology on galactic scales. We analyze a suite of Feedback in Realistic Environments simulations of 1010–1012M\u2299 halos with standard cold dark matter and compare the true circular velocity to RC reconstructions. We find that, for galaxies with well-ordered gaseous disks, the measured RC may deviate from the true circular velocity by at most ∼10% within the radius of the disk. However, nonequilibrium behaviors, noncircular motions, and nonthermal and nonkinetic stresses may cause much larger discrepancies, of ∼50% or more. Most RC reconstructions underestimate the true circular velocity, while some reconstructions transiently overestimate it in the central few kiloparsecs, due to dynamical phenomena. We further demonstrate that the features that contribute to these failures are not always visibly obvious in H I observations. If such dwarf galaxies are included in galaxy catalogs, they may give rise to the appearance of “artificial” RC diversity that does not reflect the true variation in underlying dark matter profiles.
\n
\n
The coevolution of supermassive black holes (SMBHs) and their host galaxies remains one of the central open questions in cosmology, rooted in the coupling between accretion, feedback, and the multiscale physics that links the event horizon to the circumgalactic medium. Here we bridge these scales by embedding a first-principles, GRMHD-informed prescription for black hole accretion and feedback—derived from multizone simulations that self-consistently connect inflows and outflows from the horizon to the Bondi radius—within cosmological magnetohydrodynamic zoom-in simulations of ∼1014M\u2299 halos. These GRMHD results predict a “suppressed Bondi” regime in which magnetic stresses and relativistic winds strongly reduce effective accretion rates in a spin-dependent manner. We find that black holes cannot grow efficiently by accretion until they exceed ∼107M\u2299, regardless of the feedback strength. Beyond this threshold, systems bifurcate: low-spin (η ∼ 0.02) black holes continue to accrete without quenching star formation, while high-spin (η \u2273 0.3) black holes quench effectively but become starved of further growth. Early, massive seeding partially alleviates this tension through merger-driven assembly, yet an additional cold or super-Eddington accretion mode appears essential to reproduce the observed SMBH population and the empirical black hole–galaxy scaling relations. Our results demonstrate that GRMHD-informed feedback models can account for the maintenance-mode behavior of low-luminosity active galactic nuclei like M87*, but cannot by themselves explain the full buildup of SMBH mass across cosmic time. A unified, multiregime framework is required to capture the evolving interplay between spin-dependent feedback, cold inflows, and mergers in driving coevolution.
\n
It is widely believed that the ultraviolet background produced during the epoch of reionization conspires against the formation of low-mass galaxies. Indeed, this mechanism is often invoked as part of the solution to the so-called \"missing satellites problem.\" In this paper we employ FIREbox , a large-volume cosmological simulation based on the Feedback In Realistic Environments physics model, to characterize the mechanisms governing galaxy ignition in the postreionization era. By carefully matching recently ignited halos (with stellar ages below 100 Myr at the time of selection) to halos that failed to form any stars, we conclude that the presence of cold dense gas and halo concentration helps incite the process of galaxy formation. Concretely, we find that 100% of recently ignited halos experience cold dense gas enhancements relative to their matched failed counterparts. Likewise, approximately 83% display enhancements in both cold dense gas and Navarro–Frenk–White concentration ( c NFW ), while the remaining ∼17% exhibit enhanced cold dense gas content and suppressed c NFW values. Lastly, our simulation suggests that galaxy ignition can occur as late as z = 2, potentially allowing us to observationally catch this process \"in the act\" in the foreseeable future.
",
"doi": "10.3847/1538-4357/ae29ae",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2026-02-01",
"series_number": "2",
"volume": "997",
"issue": "2",
"pages": "181"
},
{
"id": "authors:ys67b-7ws70",
"collection": "authors",
"collection_id": "ys67b-7ws70",
"cite_using_url": "https://authors.library.caltech.edu/records/ys67b-7ws70",
"type": "article",
"title": "Breaking Down the CosmoGEMS: Toward Modeling and Understanding Globular Cluster Stellar Streams in a Fully Cosmological Context",
"author": [
{
"family_name": "Panithanpaisal",
"given_name": "Nondh",
"orcid": "0000-0001-5214-8822",
"clpid": "Panithanpaisal-Nondh"
},
{
"family_name": "Sanderson",
"given_name": "Robyn E.",
"orcid": "0000-0003-3939-3297"
},
{
"family_name": "Rodriguez",
"given_name": "Carl L.",
"orcid": "0000-0003-4175-8881"
},
{
"family_name": "Starkenburg",
"given_name": "Tjitske",
"orcid": "0000-0003-2539-8206"
},
{
"family_name": "Pearson",
"given_name": "Sarah",
"orcid": "0000-0003-0256-5446"
},
{
"family_name": "Bonaca",
"given_name": "Ana",
"orcid": "0000-0002-7846-9787"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Cook",
"given_name": "Brian T.",
"orcid": "0000-0003-0341-6928"
},
{
"family_name": "Arora",
"given_name": "Arpit",
"orcid": "0000-0002-8354-7356"
},
{
"family_name": "Weatherford",
"given_name": "Newlin C.",
"orcid": "0000-0002-9660-9085"
}
],
"abstract": "Next-generation surveys are expected to uncover thousands of globular cluster (GC) stellar streams, motivating the need for a theoretical framework that produces realistic GC streams in a fully cosmological, Milky Way–like environment. We present CosmoGEMS , a star-by-star cosmological GC stream framework that self-consistently links small-scale cluster physics with large-scale Galactic dynamics. The initial phase-space positions of stream stars are informed by post-processed GC populations within the FIRE cosmological simulation. Escaped stars are orbit-integrated from their time of escape to the present day in a time-evolving Galactic potential extracted from the same simulation using a basis function expansion. We explore two example streams on different orbits. One forms a long, thin stream with a velocity dispersion consistent with Milky Way GC streams. However, it exhibits a clump and orbital-phase-dependent misalignments due to the evolving potential. The other stream develops both a thin component and a diffuse, shell-like structure, similar to features observed in streams like Jhelum. These results highlight the power of fully cosmological models in producing realistic stream morphologies and kinematics. Unlike idealized simulations, our models naturally incorporate time-dependent changes in the progenitor's orbit, including orbital plane evolution, which significantly affects stream structure. This challenges common assumptions in stream-finding algorithms and interpretation. CosmoGEMS provides a key step toward connecting future stellar stream observations with the physics of GC evolution and hierarchical galaxy formation in a cosmological context.
",
"doi": "10.3847/1538-4357/ae2ea7",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2026-02-01",
"series_number": "2",
"volume": "997",
"issue": "2",
"pages": "182"
},
{
"id": "authors:ajawd-gzq57",
"collection": "authors",
"collection_id": "ajawd-gzq57",
"cite_using_url": "https://authors.library.caltech.edu/records/ajawd-gzq57",
"type": "article",
"title": "Early Stages of Dusty Tori: The First Infrared Spectra from a Highly Multiscale Quasar Simulation",
"author": [
{
"family_name": "Bardati",
"given_name": "Jaeden",
"orcid": "0009-0002-8417-4480",
"clpid": "Bardati-Jaeden"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Richards",
"given_name": "Gordon T.",
"orcid": "0000-0002-1061-1804"
}
],
"abstract": "We present the first infrared (IR) spectral predictions from a self-consistent simulation of the formation of a quasar in a starburst galaxy, spanning the cosmological environment to scales well below the dust sublimation region. The IR emission is dominated by a torus-like dust structure composed of a highly magnetized, turbulence-supported outer accretion disk and of accreting gas tidally torn from the interstellar medium (ISM). At these early stages, the active galactic nucleus is buried and Compton thick. The near- to mid-IR escaping luminosity varies by almost an order of magnitude across sight lines, largely due to extinction from the inflowing stream of cold dust. Self-absorption within the torus suppresses silicate emission features, and further reprocessing by the ambient ISM leads to prominent silicate absorption and colder IR emission. The sublimation structure is stratified by composition and size, producing sight-line-dependent extinction curves that intrinsically vary in shape. However, after repeated scattering in the optically thick dusty medium, these curves emerge substantially grayed. We also demonstrate that bipolar outflows from the central black hole, which carves biconical cavities and reveals the central engine in later stages, can preserve IR anisotropy and silicate features. These results suggest that dusty starburst quasars can undergo a buried, IR-bright phase early in their evolution.
",
"doi": "10.3847/1538-4357/ae29af",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2026-01-20",
"series_number": "1",
"volume": "997",
"issue": "1",
"pages": "10"
},
{
"id": "authors:p9p8e-mwg36",
"collection": "authors",
"collection_id": "p9p8e-mwg36",
"cite_using_url": "https://authors.library.caltech.edu/records/p9p8e-mwg36",
"type": "article",
"title": "Strong Evidence for Cosmic-Ray-supported \u223cL* Galaxy Halos via X-Ray and tSZ Constraints",
"author": [
{
"family_name": "Ponnada",
"given_name": "Sam B.",
"orcid": "0000-0002-7484-2695",
"clpid": "Ponnada-Sam-B"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Lu",
"given_name": "Yue Samuel",
"orcid": "0009-0001-6243-0861"
},
{
"family_name": "Silich",
"given_name": "Emily M.",
"orcid": "0000-0002-1616-5649",
"clpid": "Silich-Emily-M"
},
{
"family_name": "Butsky",
"given_name": "Iryna S.",
"orcid": "0000-0003-1257-5007"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067"
}
],
"abstract": "Many state-of-the-art galaxy simulations featuring traditional feedback modes have significant challenges producing enough extended soft X-ray (∼0.5−2 keV) emission at R ∼ 0.5Rvir−1Rvir observed around galaxies with stellar masses M* \u2272 1011 M\u2299, without violating galaxy mass function constraints. Moreover, thermal Sunyaev–Zel’dovich (tSZ) measurements probing the thermal pressure of similar galaxies indicate that it is orders of magnitude lower than predictions from simple halo hydrodynamics and many hydrodynamical simulations. We demonstrate that these constraints can be met congruously with a large nonthermal pressure contribution in the form of cosmic rays (CRs) from supernovae and/or active galactic nuclei (AGN), which lowers the tSZ signal, while CR leptons produce plentiful soft X-rays via inverse Compton scattering of the cosmic microwave background. The combination of these two observations is far more constraining on the pressure budget of galactic halos than either alone—if these novel tSZ and X-ray observations are borne out by future studies, then taken together they reveal the strongest evidence for CR support in halos to date. Conversely, it is very difficult to produce the extended X-rays via traditional thermal emission without increasing the overall thermal pressure and thus tSZ signal in tandem, making these tensions even worse. Finally, tSZ and X-rays together unlock a novel observational method to constrain halo CR pressure relative to thermal pressure, with implications for CR transport parameters and AGN feedback energetics across various galaxy mass scales. Taking the currently observed constraints at Mhalo ∼ 1012 M\u2299 imply that the halo CR pressure must at least be equal to the gas thermal pressure.
",
"doi": "10.3847/2041-8213/ae2fd9",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2026-01-20",
"series_number": "1",
"volume": "997",
"issue": "1",
"pages": "L13"
},
{
"id": "authors:wyp96-exk27",
"collection": "authors",
"collection_id": "wyp96-exk27",
"cite_using_url": "https://authors.library.caltech.edu/records/wyp96-exk27",
"type": "article",
"title": "How Invisible Stellar Halos Bias Our Understanding of Ultrafaint Galaxies",
"author": [
{
"family_name": "Wheeler",
"given_name": "Coral",
"orcid": "0000-0002-2651-7281"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232"
},
{
"family_name": "Rodriguez Wimberly",
"given_name": "M. Katy",
"orcid": "0000-0003-1848-5571"
},
{
"family_name": "Mercado",
"given_name": "Francisco J.",
"orcid": "0000-0002-5908-737X",
"clpid": "Mercado-Francisco-J"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X"
},
{
"family_name": "Gandhi",
"given_name": "Pratik J.",
"orcid": "0000-0003-0965-605X"
},
{
"family_name": "Loebman",
"given_name": "Sarah R.",
"orcid": "0000-0003-3217-5967"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "\n
We explore how a realistic surface brightness (SB) detection limit of μV ≈ 32.5 mag arcsec−2 for stars at the edges of ultrafaint galaxies affects our ability to infer their underlying properties. We use a sample of 19 galaxies with stellar masses ≈400–40,000 M\u2299simulated with FIRE-2 physics and baryonic mass resolution of 30 M\u2299. The SB cut leads to smaller sizes, lower stellar masses, and lower stellar velocity dispersions than the values inferred without the cut. However, by imposing this realistic limit, our inferred galaxy properties lie closer to observed populations in the mass-size plane, better match observed velocity dispersions as a function of stellar mass, and better reproduce derived circular velocities as a function of half-light radius. For the most massive galaxies in our sample, the SB cut leads to higher mean [Fe/H] values, but the increase is not enough to match the observed MZR. Finally, we demonstrate that the common J. Wolf et al. dynamical mass estimator is less accurate when the SB cut is applied. For our lowest-mass galaxies, in particular, excluding the low-surface brightness outskirts causes us to overestimate their central dark-matter densities and virial masses. This suggests that attempts to use mass estimates of ultrafaint galaxies to constrain dark-matter physics or to place constraints on the low-mass threshold of galaxy formation must take into account surface brightness limits or risk significant biases.
\n
We study the morphology of hundreds of simulated central galaxies in the stellar mass range $M_\\star =10^{7.5} \\rm - 10^{11}~$$\\rm M_\\odot$ from the FIREbox cosmological volume. We demonstrate that FIREbox is able to predict a wide variety of morphologies, spanning from disk-dominated objects to spheroidal galaxies supported by stellar velocity dispersion. However, the simulations predict a strong relation between morphology (degree of rotational support) and stellar mass: galaxies comparable to the Milky Way are often disk-dominated while the presence of stellar disks mostly vanishes for dwarfs with M\u22c6 < 109 $\\rm M_\\odot$. This defines a \"morphology transition\" regime for galaxies with $10^9 <M_\\star /\\rm {M_\\odot }< 10^{10}$ in which disks become increasingly common, but below which disks are rare. We show that burstiness in the star formation history and the deepening of the gravitational potential strongly correlate in our simulations with this transition regime, with disks forming in objects with lower levels of burstiness in the last ∼6 Gyr and halos with mass $\\sim 10^{11} ~ \\rm {M_{\\odot }}$ and above. While observations support a transition towards thicker disks in the regime of dwarfs, our results are in partial disagreement with observations of at least some largely rotationally supported gas disks in dwarfs with M\u22c6 < 10\u2079$\\rm M_\\odot$. This study highlights dwarf morphology as a fundamental benchmark for testing future galaxy formation models.
",
"doi": "10.1093/mnras/staf1847",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2025-12",
"series_number": "4",
"volume": "544",
"issue": "4",
"pages": "4651-4664"
},
{
"id": "authors:13r4z-gwv02",
"collection": "authors",
"collection_id": "13r4z-gwv02",
"cite_using_url": "https://authors.library.caltech.edu/records/13r4z-gwv02",
"type": "article",
"title": "X-Ray Emission Signatures of Galactic Feedback in the Hot Circumgalactic Medium: Predictions from Cosmological Hydrodynamical Simulations",
"author": [
{
"family_name": "Silich",
"given_name": "Emily M.",
"orcid": "0000-0002-1616-5649",
"clpid": "Silich-Emily-M"
},
{
"family_name": "ZuHone",
"given_name": "John",
"orcid": "0000-0003-3175-2347"
},
{
"family_name": "Bellomi",
"given_name": "Elena",
"orcid": "0000-0001-6411-3686"
},
{
"family_name": "Hummels",
"given_name": "Cameron",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron"
},
{
"family_name": "Oppenheimer",
"given_name": "Benjamin",
"orcid": "0000-0002-3391-2116"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Lochhaas",
"given_name": "Cassandra",
"orcid": "0000-0003-1785-8022"
},
{
"family_name": "Ponnada",
"given_name": "Sam B.",
"orcid": "0000-0002-7484-2695",
"clpid": "Ponnada-Sam-B"
},
{
"family_name": "Vikhlinin",
"given_name": "Alexey",
"orcid": "0000-0001-8121-0234"
}
],
"abstract": "\n
Little is currently known about the physical properties of the hot circumgalactic medium (CGM) surrounding massive galaxies. Next-generation X-ray observatories will enable detailed studies of the hot CGM in emission. To support these future efforts, we make predictions of the X-ray emission from the hot CGM using a sample of 28 ∼Milky Way-mass disk galaxies at z = 0 from seven cosmological hydrodynamical simulation suites incorporating a wide range of galactic feedback prescriptions. The X-ray surface brightness (XSB) morphology of the hot CGM varies significantly across simulations. XSB-enhanced outflows and bubble-like structures are predicted in many galaxies simulated with active galactic nuclei (AGN) feedback and in some stellar-feedback-only galaxies, while other galaxies exhibit more isotropic XSB distributions at varying brightnesses. Galaxies simulated without cosmic-ray physics exhibit radial XSB profiles with similar shapes (∝r−3 within 20–200 kpc), with scatter about this slope likely due to underlying feedback physics. The hot CGM kinematics also differ substantially: velocity maps reveal signatures of bulk CGM rotation and high-velocity biconical outflows, particularly in simulations incorporating AGN feedback. Some stellar-feedback-only models also generate similar AGN-like outflows, which we postulate is due to centrally concentrated star formation. Simulations featuring AGN feedback frequently produce extended temperature enhancements in large-scale galactic outflows, while simulations incorporating cosmic-ray physics predict the coolest CGM due to pressure support being provided by cosmic rays rather than hot CGM. Individually resolved X-ray emission lines further distinguish hot CGM phases, with lower-energy lines (e.g., O VII) largely tracing volume-filling gas, and higher-energy lines (e.g., Fe XVII) highlighting high-velocity feedback-driven outflows.
\n
The centers of massive elliptical galaxies exhibit a wide range in density profiles, from central cusps to resolved cores with order kiloparsec sizes. The cored ellipticals have been linked to the presence of supermassive black hole binaries that excavate their hosts' central stellar populations through three-body encounters. This connection between cores and black holes similarly operates in globular clusters, which also exhibit a bimodality in cored and core-collapsed architectures, rich and depleted, respectively, in stellar black holes. We report new estimates of the total black hole mass in 25 Galactic globular clusters based on a suite of roughly 150 Monte Carlo N -body simulations that fit observed surface brightness and velocity dispersion profiles. We show that both globular clusters and massive elliptical galaxies individually exhibit strong correlations between total black hole mass ( M • ) and core radius ( r c ) and that these individual relations share a common power-law exponent to within 1 σ statistical precision: M• ∼ r_c^(1.3). The individual relations appear to be offset, suggesting swarms of stellar black holes scour globular cluster cores more efficiently than lone supermassive black holes scour the cores of massive ellipticals. Yet the shared basis of core scouring via black hole binaries hints at a unified M• – r_c connection across over 10 orders of magnitude in M•. Our findings imply core radius measurements may offer a powerful observational constraint on black hole merger rates, from kilohertz sources detectable by LIGO/Virgo/KAGRA formed in globular clusters to millihertz and nanohertz sources formed in massive elliptical galaxies.
",
"doi": "10.3847/2041-8213/ae1233",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2025-11-01",
"series_number": "1",
"volume": "993",
"issue": "1",
"pages": "L34"
},
{
"id": "authors:sejnp-eqt72",
"collection": "authors",
"collection_id": "sejnp-eqt72",
"cite_using_url": "https://authors.library.caltech.edu/records/sejnp-eqt72",
"type": "article",
"title": "Central densities of dark matter haloes in FIRE-2 simulations of low-mass galaxies with cold dark matter and self-interacting dark matter",
"author": [
{
"family_name": "Straight",
"given_name": "Maria C",
"orcid": "0009-0000-2266-1465"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X"
},
{
"family_name": "Bullock",
"given_name": "James S",
"orcid": "0000-0003-4298-5082"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Shen",
"given_name": "Xuejian",
"orcid": "0000-0002-6196-823X"
},
{
"family_name": "Necib",
"given_name": "Lina",
"orcid": "0000-0003-2806-1414",
"clpid": "Necib-L"
},
{
"family_name": "Lazar",
"given_name": "Alexandres",
"orcid": "0000-0002-6852-6282"
},
{
"family_name": "Graus",
"given_name": "Andrew S"
},
{
"family_name": "Samuel",
"given_name": "Jenna",
"orcid": "0000-0002-8429-4100"
}
],
"abstract": "We investigate the central density structure of dark matter haloes in cold dark matter (CDM) and self-interacting dark matter (SIDM) models using simulations that are part of the Feedback In Realistic Environments (fire) project. For simulated haloes of dwarf galaxy scale (M_(halo)(z=0) ≈ 10¹\u2070M\u2299, we study the central structure in both dissipationless simulations and simulations with full fire-2 galaxy formation physics. As has been demonstrated extensively in recent years, both baryonic feedback and self-interactions can convert central cusps into cores, with the former process doing so in a manner that depends sensitively on stellar mass at fixed M_(halo). Whether the two processes (baryonic feedback and self-interactions) are distinguishable, however, remains an open question. Here we demonstrate that, compared to feedback-induced cores, SIDM-induced cores transition more quickly from the central region of constant density to the falling density at larger radial scales. This result holds true even when including identical galaxy formation modelling in SIDM simulations as is used in CDM simulations, since self-interactions dominate over galaxy formation physics in establishing the central structure of SIDM haloes in this mass regime. The change in density profile slope as a function of radius therefore holds the potential to discriminate between self-interactions and galaxy formation physics as the driver of core formation in dwarf galaxies.
",
"doi": "10.1093/mnras/staf1539",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2025-11",
"series_number": "3",
"volume": "543",
"issue": "3",
"pages": "1995-2005"
},
{
"id": "authors:5a2mg-8sv86",
"collection": "authors",
"collection_id": "5a2mg-8sv86",
"cite_using_url": "https://authors.library.caltech.edu/records/5a2mg-8sv86",
"type": "article",
"title": "Connection between galaxy morphology and dark-matter halo structure I: a running threshold for thin discs and size predictors from the dark sector",
"author": [
{
"family_name": "Liang",
"given_name": "Jinning",
"orcid": "0000-0001-8405-2921"
},
{
"family_name": "Jiang",
"given_name": "Fangzhou",
"orcid": "0000-0001-6115-0633"
},
{
"family_name": "Mo",
"given_name": "Houjun",
"orcid": "0000-0001-5356-2419"
},
{
"family_name": "Benson",
"given_name": "Andrew",
"orcid": "0000-0001-5501-6008",
"clpid": "Benson-A-J"
},
{
"family_name": "Dekel",
"given_name": "Avishai",
"orcid": "0000-0003-4174-0374"
},
{
"family_name": "Tavron",
"given_name": "Noa"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Ho",
"given_name": "Luis C"
}
],
"abstract": "We study the connection between galaxy morphology and host dark matter (DM) halo structure using cosmological simulations. Introducing a new kinematic decomposition scheme, we robustly separate thin and thick discs and measure halo properties, including cosmic web locations, internal structures, and assembly histories. In the TNG50 simulation, we find that the orbital-circularity threshold for disc differentiation varies systematically with galaxy mass and redshift. Similarly, the energy threshold between stellar haloes and inner galaxies depends on mass and redshift, minimizing at sub-Galactic halo mass where the circularity threshold approaches its peak. Revisiting galaxy size predictors, we show that disc sizes in TNG50 correlate with three structural parameters beyond virial mass and redshift: (1) a positive correlation with halo spin λ across redshifts – stronger than previously reported for zoom-in simulations but still weaker than the simple r_(1/2)/R_(vir) ∝ λ caling; (2) an anticorrelation with DM concentration c; (3) larger discs in more actively accreting haloes. Disc mass fraction is higher in rounder haloes and in cosmic knots and filaments, implying that disc development needs both stable halo conditions and continuous material supply. Our methodology is public and adaptable to other simulations.
",
"doi": "10.1093/mnras/staf947",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2025-08",
"series_number": "3",
"volume": "541",
"issue": "3",
"pages": "2304-2323"
},
{
"id": "authors:jd0k6-yqh28",
"collection": "authors",
"collection_id": "jd0k6-yqh28",
"cite_using_url": "https://authors.library.caltech.edu/records/jd0k6-yqh28",
"type": "article",
"title": "The Physical Origin of Positive Metallicity Radial Gradients in High-redshift Galaxies: Insights from the FIRE-2 Cosmological Hydrodynamic Simulations",
"author": [
{
"family_name": "Sun",
"given_name": "Xunda",
"orcid": "0009-0005-8170-5153"
},
{
"family_name": "Wang",
"given_name": "Xin",
"orcid": "0000-0002-9373-3865"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349"
},
{
"family_name": "Wang",
"given_name": "Kai",
"orcid": "0000-0002-3775-0484"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067"
},
{
"family_name": "Graf",
"given_name": "Russell L.",
"orcid": "0009-0009-8310-8992"
},
{
"family_name": "Marszewski",
"given_name": "Andrew"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565"
},
{
"family_name": "Sun",
"given_name": "Guochao",
"orcid": "0000-0003-4070-497X"
},
{
"family_name": "Sun",
"given_name": "Lei",
"orcid": "0009-0004-6325-7839"
},
{
"family_name": "Thyme",
"given_name": "Keyer"
}
],
"abstract": "Using the FIRE-2 cosmological zoom-in simulations, we investigate the temporal evolution of gas-phase metallicity radial gradients of Milky Way–mass progenitors in the redshift range of 0.4 < z < 3. We pay special attention to the occurrence of positive (i.e., inverted) metallicity gradients—where metallicity increases with galactocentric radius. This trend, contrary to the more commonly observed negative radial gradients, has been frequently seen in recent spatially resolved grism observations. The rate of occurrence of positive gradients in FIRE-2 is about ∼7% for 0.4 < z < 3 and ∼13% at higher redshifts (1.5 < z < 3), broadly consistent with observations. Moreover, we investigate the correlations among galaxy metallicity gradient, stellar mass, star formation rate (SFR), and degree of rotational support. Metallicity gradients show a strong correlation with both sSFR and the rotational-to-dispersion velocity ratio (vc/σ), implying that starbursts and kinematic morphology of galaxies play significant roles in shaping these gradients. The FIRE-2 simulations indicate that galaxies with high sSFR (log(sSFR[yr−1])\u2273−9.2) and weak rotational support (vc/σ \u2272 1) are more likely—by ∼15%—to develop positive metallicity gradients. This trend is attributed to galaxy-scale gas flows driven by stellar feedback, which effectively redistribute metals within the interstellar medium. Our results support the important role of stellar feedback in governing the chemo-structural evolution and disk formation of Milky Way–mass galaxies at the cosmic noon epoch.
",
"doi": "10.3847/1538-4357/addab5",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2025-06-20",
"series_number": "2",
"volume": "986",
"issue": "2",
"pages": "179"
},
{
"id": "authors:kf0hx-vak56",
"collection": "authors",
"collection_id": "kf0hx-vak56",
"cite_using_url": "https://authors.library.caltech.edu/records/kf0hx-vak56",
"type": "article",
"title": "Dust Battery: A Novel Mechanism for Seed Magnetic Field Generation in the Early Universe",
"author": [
{
"family_name": "Soliman",
"given_name": "Nadine H.",
"orcid": "0000-0002-6810-1110",
"clpid": "Soliman-Nadine-H"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X"
}
],
"abstract": "\n
We propose a novel dust battery mechanism for generating seed magnetic fields in the early Universe, in which charged dust grains are radiatively accelerated, inducing strong electric currents that subsequently generate magnetic fields. Our analysis demonstrates that this process is effective even at very low metallicities (approximately ∼10−5Z\u2299), and capable of producing seed fields with significant amplitudes of B ∼ μG around luminous sources over timescales of years to Myr and across spatial scales ranging from au to kpc. Crucially, we find that this mechanism is generically ∼108 times more effective than the radiatively driven electron battery or Biermann battery in relatively cool gas (\u226a105 K), including both neutral and ionized gas. Furthermore, our results suggest that, to first order, dissipation effects do not appear to significantly impede this process, and that it can feasibly generate coherent seed fields on macroscopically large interstellar medium (ISM) scales (much larger than turbulent dissipation scales or electron mean-free-paths in the ISM). These seed fields could then be amplified by subsequent dynamo actions to the observed magnetic fields in galaxies. Additionally, we propose a subgrid model for integration into cosmological simulations, and the required electric-field expressions for magnetohydrodynamic-particle-in-a-cell simulations that explicitly model dust dynamics. Finally, we explore the broad applicability of this mechanism across different scales and conditions, emphasizing its robustness compared to other known battery mechanisms.
\n
We utilize the cosmological volume simulation FIREbox to investigate how a galaxy's environment influences its size and dark matter content. Our study focuses on approximately 1200 galaxies (886 central and 332 satellite halos) in the low-mass regime, with stellar masses between 106 and 109M\u2299. We analyze the size–mass relation (r50–M\u22c6), the inner dark matter mass–stellar mass (M_(DM)50–M\u22c6) relation, and the halo mass–stellar mass (Mhalo–M\u22c6) relation. At fixed stellar mass, we find that galaxies experiencing stronger tidal influences, indicated by higher Perturbation Indices (PI > 1) are generally larger and have lower halo masses relative to their counterparts with lower Perturbation Indices (PI < 1). Applying a Random Forest regression model, we show that both the environment (PI) and halo mass (Mhalo) are significant predictors of a galaxy's relative size and dark matter content. Notably, because Mhalo is also strongly affected by the environment, our findings indicate that environmental conditions not only influence galactic sizes and relative inner dark matter content directly, but also indirectly, through their impact on halo mass. Our results highlight a critical interplay between environmental factors and halo mass in shaping galaxy properties, affirming the environment as a fundamental driver in galaxy formation and evolution.
",
"doi": "10.3847/1538-4357/adbf07",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2025-04-20",
"series_number": "2",
"volume": "983",
"issue": "2",
"pages": "93"
},
{
"id": "authors:2kw2x-kfh68",
"collection": "authors",
"collection_id": "2kw2x-kfh68",
"cite_using_url": "https://authors.library.caltech.edu/records/2kw2x-kfh68",
"type": "article",
"title": "Aggressively Dissipative Dark Dwarfs: The Effects of Atomic Dark Matter on the Inner Densities of Isolated Dwarf Galaxies",
"author": [
{
"family_name": "Roy",
"given_name": "Sandip",
"orcid": "0000-0002-7638-7454"
},
{
"family_name": "Shen",
"given_name": "Xuejian",
"orcid": "0000-0002-6196-823X"
},
{
"family_name": "Barron",
"given_name": "Jared",
"orcid": "0000-0001-9043-6577"
},
{
"family_name": "Lisanti",
"given_name": "Mariangela",
"orcid": "0000-0002-8495-8659"
},
{
"family_name": "Curtin",
"given_name": "David",
"orcid": "0000-0003-0263-6195"
},
{
"family_name": "Murray",
"given_name": "Norman",
"orcid": "0000-0002-8659-3729"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We present the first suite of cosmological hydrodynamical zoom-in simulations of isolated dwarf galaxies for a dark sector that consists of cold dark matter and a strongly dissipative subcomponent. The simulations are implemented in GIZMO and include standard baryons following the FIRE-2 galaxy formation physics model. The dissipative dark matter is modeled as atomic dark matter (aDM), which forms a dark hydrogen gas that cools in direct analogy to the Standard Model. Our suite includes seven different simulations of ∼1010 M\u2299 systems that vary over the aDM microphysics and the dwarf's evolutionary history. We identify a region of aDM parameter space where the cooling rate is aggressive and the resulting halo density profile is universal. In this regime, the aDM gas cools rapidly at high redshifts, and only a small fraction survives in the form of a central dark gas disk; the majority collapses centrally into collisionless dark \"clumps,\" which are clusters of subresolution dark compact objects. These dark clumps rapidly equilibrate in the inner galaxy, resulting in an approximately isothermal distribution that can be modeled with a simple fitting function. Even when only a small fraction (∼5%) of the total dark matter is strongly dissipative, the central densities of classical dwarf galaxies can be enhanced by over an order of magnitude, providing a sharp prediction for observations.
",
"doi": "10.3847/1538-4357/adb02b",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2025-04-01",
"series_number": "2",
"volume": "982",
"issue": "2",
"pages": "175"
},
{
"id": "authors:kq6bz-gdy07",
"collection": "authors",
"collection_id": "kq6bz-gdy07",
"cite_using_url": "https://authors.library.caltech.edu/records/kq6bz-gdy07",
"type": "article",
"title": "Cosmological Predictions for Minor Axis Stellar Density Profiles in the Inner Regions of Milky Way\u2013mass Galaxies",
"author": [
{
"family_name": "Lucey",
"given_name": "Madeline",
"orcid": "0000-0001-7297-8508"
},
{
"family_name": "Sanderson",
"given_name": "Robyn E.",
"orcid": "0000-0003-3939-3297"
},
{
"family_name": "Horta",
"given_name": "Danny",
"orcid": "0000-0003-1856-2151"
},
{
"family_name": "Kundu",
"given_name": "Aritra",
"orcid": "0000-0001-8746-4753"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Arora",
"given_name": "Arpit",
"orcid": "0000-0002-8354-7356"
},
{
"family_name": "Singh",
"given_name": "Jasjeev",
"orcid": "0009-0008-8901-2206"
},
{
"family_name": "Panithanpaisal",
"given_name": "Nondh",
"orcid": "0000-0001-5214-8822",
"clpid": "Panithanpaisal-Nondh"
}
],
"abstract": "\n
ΛCDM cosmology predicts the hierarchical formation of galaxies, which build up mass by merger events and accreting smaller systems. The stellar halo of the Milky Way (MW) has proven to be useful a tool for tracing this accretion history. However, most of this work has focused on the outer halo where dynamical times are large and the dynamical properties of accreted systems are preserved. In this work, we investigate the inner galaxy regime, where dynamical times are relatively small and systems are generally completely phase mixed. Using the FIRE-2 and Auriga cosmological zoom-in simulation suites of MW-mass galaxies, we find the stellar density profiles along the minor axis (perpendicular to the galactic disk) within the Navarro–Frenk–White scale radii (R ≈ 15 kpc) are best described as an exponential disk with scale height < 0.3 kpc and a power-law component with slope α ≈ −4. The stellar density amplitude and slope for the power-law component are not significantly correlated with metrics of the galaxy's accretion history. Instead, we find the stellar profiles strongly correlate with the dark matter profile. Across simulation suites, the galaxies studied in this work have a stellar-to-dark-matter mass ratio that decreases as 1/r2 along the minor axis.
\n
\n
Coupling black hole (BH) feeding and feedback involves interactions across vast spatial and temporal scales that are computationally challenging to model. Tracking gas inflows and outflows from kiloparsec scales to the event horizon for non-spinning BHs in the presence of strong magnetic fields, H. Cho et al. report strong suppression of accretion on horizon scales and low (2%) feedback efficiency. In this letter, we explore the impact of these findings for the supermassive BHs M87* and Sgr A*, using high-resolution, non-cosmological, magnetohydrodynamic simulations with the FIRE-2 model. Without feedback, we find rapid BH growth due to “cooling flows,” with 2% feedback efficiency, while accretion is suppressed, the rates still remain higher than constraints from Event Horizon Telescope (EHT) data for M87* and Sgr A*. To match the EHT observations of M87*, an efficiency greater than 15% is required, suggesting the need to include enhanced feedback from BH spin. Similarly, a feedback efficiency of >15% is needed for Sgr A* to match the observationally estimated star formation rate of \u22722M\u2299 yr−1. Even with 100% feedback efficiency, the simulation-predicted Sgr A* accretion rate remains higher than EHT-inferred levels on average, while only episodically matching it, suggesting that Sgr A* is currently in a temporary quiescent phase. Bridging accretion and feedback across scales, we conclude that higher feedback efficiencies, possibly due to nonzero BH spin, are necessary to suppress “cooling flows” and match both the observed accretion and star formation rates in M87* and Sgr A*.
\n
We infer supermassive black hole (SMBH) accretion rates and Eddington ratios as a function of SMBH/host galaxy mass and redshift with the empirical Trinity model of dark matter halo–galaxy–SMBH connection. The galaxy–SMBH mass and growth rate connection from Trinity match galaxy observables from 0 < z < 13 and SMBH observables from 0 < z < 6.5\u2060. Key findings include: (1) the ratio between cosmic SMBH accretion rate and galaxy star formation rate stays constant at ~ 2 x 10\u207b³ from z = 0 - 4\u2060, and decreases by 2 orders of magnitude from \u2060z = 4 -10; (2) the average SMBH Eddington ratio η increases towards higher redshifts, nearly reaching η = 1 at \u2060z ~ 10; (3) at fixed redshift for z < 3\u2060, SMBHs/galaxies with higher masses have lower \u2060η, consistent with active galactic nucleus (AGN) downsizing; (4) the average ratio of specific SMBH accretion rate (SBHAR\u2060\u2060) to average specific star formation rate (SSFR\u2060\u2060) is nearly mass-independent, with a value SBHAR/SSFR ~ 1\u2060, which decreases slightly from z = 10 to z = 0\u2060; (5) similar to galaxies, SMBHs reach their peak efficiency to convert baryons into mass when host haloes reach 10¹² M\u2299; (6) given galaxy and SMBH growth histories from Trinity, the local descendants of 1 < z < 11 overmassive JWST AGNs will remain outliers from the local SMBH mass–galaxy mass relation. These findings combine to give a simple explanation for massive (10\u2079 - 10¹\u2070\u2060\u2060) quasars at \u2060z > 6: at these redshifts, dark matter haloes grow with an e-folding time of ~ 45 Myr, driving similar growth in both galaxies and SMBHs.
",
"doi": "10.1093/mnras/staf260",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2025-03",
"series_number": "1",
"volume": "538",
"issue": "1",
"pages": "503-517"
},
{
"id": "authors:mbr2z-4bh84",
"collection": "authors",
"collection_id": "mbr2z-4bh84",
"cite_using_url": "https://authors.library.caltech.edu/records/mbr2z-4bh84",
"type": "article",
"title": "Hooks, Lines, and Sinkers: How Active Galactic Nucleus Feedback and Cosmic-Ray Transport Shape the Far-infrared\u2013Radio Correlation of Galaxies",
"author": [
{
"family_name": "Ponnada",
"given_name": "Sam B.",
"orcid": "0000-0002-7484-2695",
"clpid": "Ponnada-Sam-B"
},
{
"family_name": "Cochrane",
"given_name": "Rachel K.",
"orcid": "0000-0001-8855-6107"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Butsky",
"given_name": "Iryna S.",
"orcid": "0000-0003-1257-5007"
},
{
"family_name": "Wellons",
"given_name": "Sarah",
"orcid": "0000-0002-3977-2724"
},
{
"family_name": "Sanchez",
"given_name": "N. Nicole",
"orcid": "0000-0001-7589-6188",
"clpid": "Sanchez-N-Nicole"
},
{
"family_name": "Hummels",
"given_name": "Cameron",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron"
},
{
"family_name": "Lu",
"given_name": "Yue Samuel"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236"
}
],
"abstract": "\n
The far-infrared–radio correlation (FRC) is one of the most promising empirical constraints on the role of cosmic rays (CRs) and magnetic fields in galaxy formation and evolution. While many theories have been proposed in order to explain the emergence and maintenance of the FRC across a gamut of galaxy properties and redshift, the nonlinear physics at play remain unexplored in full complexity and within a cosmological context. We present the first reproduction of the z ∼ 0 FRC using detailed synthetic observations of state-of-the-art cosmological zoom-in simulations from the Feedback in Realistic Environments (FIRE-3) suite with explicitly evolved CR proton and electron (CRe) spectra, for three models for CR transport and multichannel active galactic nucleus (AGN) feedback. In doing so, we generally verify the predictions of \"calorimeter\" theories at high FIR luminosities (L60 μm \u2273 109.5 L\u2299) and at low FIR luminosities (L60 μm \u2272 109.5 L\u2299), the so-called \"conspiracy\" of increasing UV radiation escape in tandem with increasing CRe escape, and find that the global FRC is insensitive to orders-of-magnitude locally variable CR transport coefficients. Importantly, the indirect effect of AGN feedback on emergent observables highlights novel interpretations of outliers in the FRC. In particular, we find that in many cases \"radio-excess\" objects can be better understood as \"IR-dim\" objects with longer-lived radio contributions at low z from Type Ia supernovae and intermittent black hole accretion in quenching galaxies, though this is sensitive to the interplay of CR transport and AGN feedback physics. This creates characteristic evolutionary tracks leading to the z = 0 FRC, which shape the subsequent late-time behavior of each model.
\n
\n
Quasars are powered by supermassive black hole (SMBH) accretion disks, yet standard thin disk models are inconsistent with many observations. Recently, P. F. Hopkins et al. simulated the formation of a quasar disk feeding an SMBH of mass M = 1.3 × 107 M\u2299 in a galaxy. The disk had surprisingly strong toroidal magnetic fields that supported it vertically from gravity and powered rapid accretion. What feedback can such a system produce? To answer this, we must follow the gas to the event horizon. For this, we interpolated the quasar into the general-relativistic radiation magnetohydrodynamics code H-AMR and performed 3D simulations with BH spins a = 0 and a = 0.9375. This remapping generates magnetic monopoles, which we erase using a novel divergence cleaning approach. Despite the toroidal magnetic field's dominance at large radii, vertical magnetic flux builds up near the event horizon, leading to a magnetic state transition within the inner 200 gravitational radii of the disk. This powers strong winds and, for spinning BHs, relativistic jets that can spin down the BH within 5−10 Myr. Sometimes, vertical magnetic fields of opposite polarity reach the BH, causing a polarity inversion event that briefly destroys the jets and, possibly, the X-ray corona. These strong fields power accretion at rates 5× the Eddington limit, which can double the BH mass in 5–10 Myr. When a = 0.9375 (a = 0), the energy in mechanical outflows and radiation equals about 60% (10%) and 100% (3%) of the accreted rest mass energy, respectively. Much of the light escapes in cool, \u22731300 au photospheres, consistent with quasar microlensing and spectral energy distributions.
\n
\n
Numerous stars exhibit surprisingly large variations in their refractory element abundances, often interpreted as signatures of planetary ingestion events. In this study, we propose that differences in the dust-to-gas ratio near stars during their formation can produce similar observational signals. We investigate this hypothesis using a suite of radiation-dust-magnetohydrodynamic STAR FORmation in Gaseous Environments (or STARFORGE) simulations of star formation. Our results show that the distribution of refractory abundance variations (Δ[X/H]) has extended tails, with about 10%–30% of all stars displaying variations around ∼0.1 dex. These variations are comparable to the accretion of 2–5 M⊕ of planetary material into the convective zones of Sun-like stars. The width of the distributions increases with the incorporation of more detailed dust physics, such as radiation pressure and back-reaction forces, as well as with larger dust grain sizes and finer resolutions. Furthermore, our simulations reveal no correlation between Δ[X/H] and stellar separations, suggesting that dust-to-gas fluctuations likely occur on scales smaller than those of wide binaries. These findings highlight the importance of considering dust dynamics as a potential source of the observed chemical enrichment in stars.
\n
\n
Simulations and observations suggest that galaxy interactions may enhance the star formation rate (SFR) in merging galaxies. One proposed mechanism is the torque exerted on the gas and stars in the larger galaxy by the smaller galaxy. We analyze the interaction torques and star formation activity on six galaxies from the FIRE-2 simulation suite with masses comparable to the Milky Way galaxy at redshift z = 0. We trace the halos from z = 3.6 to z = 0, calculating the torque exerted by the nearby galaxies on the gas in the central galaxy. We calculate the correlation between the torque and the SFR across the simulations for various mass ratios. For near-equal-stellar-mass-ratio interactions in the galaxy sample, occurring between z = 1.2−3.6, there is a positive and statistically significant correlation between the torque from nearby galaxies on the gas of the central galaxies and the SFR. For all other samples, no statistically significant correlation is found between the torque and the SFR. Our analysis shows that some, but not all, major interactions cause starbursts in the simulated Milky Way-mass galaxies, and that most starbursts are not caused by galaxy interactions. The transition from “bursty” at high redshift (z \u2273 1) to “steady” star formation state at later times is independent of the interaction history of the galaxies, and most of the interactions do not leave significant imprints on the overall trend of the star formation history of the galaxies.
\n
\n
The physical mechanisms responsible for bar formation and destruction in galaxies remain a subject of debate. While we have gained valuable insight into how bars form and evolve from isolated idealized simulations, in the cosmological domain, galactic bars evolve in complex environments, with mergers and gas accretion events occurring in the presence of the turbulent interstellar medium with multiple star formation episodes, in addition to coupling with their host galaxies’ dark matter halos. We investigate the bar formation in 13 Milky Way–mass galaxies from the Feedback in Realistic Environments (FIRE-2) cosmological zoom-in simulations. 8 of the 13 simulated galaxies form bars at some point during their history: three from tidal interactions and five from internal evolution of the disk. The bars in FIRE-2 are generally shorter than the corotation radius (mean bar radius ∼1.53 kpc), have a wide range of pattern speeds (36–97 km s−1 kpc−1), and live for a wide range of dynamical times (2–160 bar rotations). We find that the bar formation in FIRE-2 galaxies is influenced by satellite interactions and the stellar-to-dark-matter mass ratio in the inner galaxy, but neither is a sufficient condition for bar formation. Bar formation is more likely to occur, with the bars formed being stronger and longer-lived, if the disks are kinematically cold; galaxies with high central gas fractions and/or vigorous star formation, on the other hand, tend to form weaker bars. In the case of the FIRE-2 galaxies, these properties combine to produce ellipsoidal bars with strengths A2/A0 ∼ 0.1–0.2.
\n
\n
We make an in-depth analysis of different active galactic nuclei (AGN) jet models’ signatures, inducing quiescence in galaxies with a halo mass of 1012M\u2299. Three jet models, including cosmic-ray-dominant, hot thermal, and precessing kinetic jets, are studied at two energy flux levels each, compared to a jet-free, stellar feedback-only simulation. Each of our simulations is idealized isolated galaxy simulations with AGN jet powers that are constant in time and generated using GIZMO and with FIRE stellar feedback. We examine the distribution of Mg ii, O vi, and O viii ions, alongside gas temperature and density profiles. Low-energy ions, like Mg ii, concentrate in the interstellar medium (ISM), while higher energy ions, e.g., O viii, prevail at the AGN jet cocoon’s edge. High-energy flux jets display an isotropic ion distribution with lower overall density. High-energy thermal or cosmic-ray jets pressurize at smaller radii, significantly suppressing core density. The cosmic-ray jet provides extra pressure support, extending cool and warm gas distribution. A break in the ion-to-mass ratio slope in O vi and O viii is demonstrated in the ISM-to-circumgalactic medium (CGM) transition (between 10 and 30 kpc), growing smoothly toward the CGM at greater distances.
\n
The cold (∼10\u2074 K) component of the circumgalactic medium (CGM) accounts for a significant fraction of all galactic baryons. However, using current galaxy-scale simulations to determine the origin and evolution of cold CGM gas poses a significant challenge, since it is computationally infeasible to directly simulate a galactic halo alongside the sub-pc scales that are crucial for understanding the interactions between cold CGM gas and the surrounding 'hot' medium. In this work, we introduce a new approach: the Cold Gas Subgrid Model (CGSM), which models unresolved cold gas as a second fluid in addition to the standard 'normal' gas fluid. The CGSM tracks the total mass density and bulk momentum of unresolved cold gas, deriving the properties of its unresolved cloudlets from the resolved gas phase. The interactions between the subgrid cold fluid and the resolved fluid are modeled by prescriptions from high-resolution simulations of 'cloud crushing' and thermal instability. Through a series of idealized tests, we demonstrate the CGSM's ability to overcome the resolution limitations of traditional hydrodynamics simulations, successfully capturing the correct cold gas mass, its spatial distribution, and the timescales for cloud destruction and growth. We discuss the implications of using this model in cosmological simulations to more accurately represent the microphysics that govern the galactic baryon cycle.
",
"doi": "10.1093/mnras/stae2459",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-12",
"series_number": "2",
"volume": "535",
"issue": "2",
"pages": "1672-1683"
},
{
"id": "authors:jegxq-fkf91",
"collection": "authors",
"collection_id": "jegxq-fkf91",
"cite_using_url": "https://authors.library.caltech.edu/records/jegxq-fkf91",
"type": "article",
"title": "Any way the wind blows: quantifying superbubbles and their outflows in simulated galaxies across z \u2248 0-3",
"author": [
{
"family_name": "Porter",
"given_name": "Lori E.",
"orcid": "0000-0002-7795-2267"
},
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081"
},
{
"family_name": "Burkhart",
"given_name": "Blakesley",
"orcid": "0000-0001-5817-5944"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We present an investigation of clustered stellar feedback in the form of superbubbles identified within eleven galaxies from the FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulation suite, at both cosmic noon (1 < z < 3) and in the local Universe. We study the spatially-resolved multiphase outflows that these supernovae drive, comparing our findings with recent theory and observations. These simulations consist of five LMC-mass galaxies and six Milky Way-mass progenitors (with a minimum baryonic particle mass of m_(b.min) = 7100 M\u2299). For all galaxies, we calculate the local and galaxy-averaged mass and energy loading factors from the identified outflows. We also characterize the multiphase morphology and properties of the identified superbubbles, including the 'shell' of cool (T < 10\u2075 K) gas and break out of energetic hot (T > 10\u2075 K) gas when the shell bursts. We find that these simulations, regardless of redshift, have mass-loading factors and momentum fluxes in the cool gas that largely agree with recent observations. Lastly, we also investigate how methodological choices in measuring outflows can affect loading factors for galactic winds.
",
"doi": "10.1093/mnras/stae2576",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-12",
"series_number": "4",
"volume": "535",
"issue": "4",
"pages": "3451-3469"
},
{
"id": "authors:m800t-fgk63",
"collection": "authors",
"collection_id": "m800t-fgk63",
"cite_using_url": "https://authors.library.caltech.edu/records/m800t-fgk63",
"type": "article",
"title": "Thermodynamics of Giant Molecular Clouds: The Effects of Dust Grain Size",
"author": [
{
"family_name": "Soliman",
"given_name": "Nadine H.",
"orcid": "0000-0002-6810-1110",
"clpid": "Soliman-Nadine-H"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604"
}
],
"abstract": "\n
The dust grain size distribution (GSD) likely varies significantly across star-forming environments in the Universe, but its impact on star formation remains unclear. This ambiguity arises because the GSD interacts nonlinearly with processes like heating, cooling, radiation, and chemistry, which have competing effects and varying environmental dependencies. Processes such as grain coagulation, expected to be efficient in dense star-forming regions, reduce the abundance of small grains and increase that of larger grains. Motivated by this, we investigate the effects of similar GSD variations on the thermochemistry and evolution of giant molecular clouds (GMCs) using magnetohydrodynamic simulations spanning a range of cloud masses and grain sizes, which explicitly incorporate the dynamics of dust grains within the full-physics framework of the STARFORGE project. We find that grain size variations significantly alter GMC thermochemistry: the leading-order effect is that larger grains, under fixed dust mass, GSD dynamic range, and dust-to-gas ratio, result in lower dust opacities. This reduced opacity permits interstellar radiation field and internal radiation photons to penetrate more deeply. This leads to rapid gas heating and inhibited star formation. Star formation efficiency is highly sensitive to grain size, with an order-of-magnitude reduction when grain size dynamic range increases from 10−3–0.1 μm to 0.1–10 μm. Additionally, warmer gas suppresses low-mass star formation, and decreased opacities result in a greater proportion of gas in diffuse ionized structures.
\n
Context. The detection of supermassive black holes (SMBHs) in high-redshift luminous quasars may require a phase of rapid accretion, and as a precondition, substantial gas influx toward seed black holes (BHs) from kiloparsec or parsec scales. Our previous research demonstrated the plausibility of such gas supply for BH seeds within star-forming giant molecular clouds (GMCs) with high surface density (∼10\u2074\u2006M\u2299\u2006pc\u207b²), facilitating \"hyper-Eddington\" accretion via efficient feeding by dense clumps, which are driven by turbulence and stellar feedback. Aims. This article presents an investigation of the impacts of feedback from accreting BHs on this process, including radiation, mechanical jets, and highly relativistic cosmic rays. Methods. We ran a suite of numerical simulations to explore diverse parameter spaces of BH feedback, including the subgrid accretion model, feedback energy efficiency, mass loading factor, and initial metallicity. Results. Using radiative feedback models inferred from the slim disk, we find that hyper-Eddington accretion is still achievable, yielding BH bolometric luminosities of as high as 10\u2074¹\u2005−\u200510\u2074\u2074\u2006erg/s, depending on the GMC properties and specific feedback model assumed. We find that the maximum possible mass growth of seed BHs (ΔM_(max)^(BH)) is regulated by the momentum-deposition rate from BH feedback, \u1e57feedback/(\u1e40_(BH)c), which leads to an analytic scaling that agrees well with simulations. This scenario predicts the rapid formation of ∼10\u2074 M\u2299 intermediate-massive BHs (IMBHs) from stellar-mass BHs within ∼1 Myr. Furthermore, we examine the impacts of subgrid accretion models and how BH feedback may influence star formation within these cloud complexes.
",
"doi": "10.1051/0004-6361/202450964",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy and Astrophysics",
"publication_date": "2024-11",
"volume": "691",
"pages": "A24"
},
{
"id": "authors:9bcet-kfd47",
"collection": "authors",
"collection_id": "9bcet-kfd47",
"cite_using_url": "https://authors.library.caltech.edu/records/9bcet-kfd47",
"type": "article",
"title": "Dust-evacuated Zones near Massive Stars: Consequences of Dust Dynamics on Star-forming Regions",
"author": [
{
"family_name": "Soliman",
"given_name": "Nadine H.",
"orcid": "0000-0002-6810-1110",
"clpid": "Soliman-Nadine-H"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604"
}
],
"abstract": "\n
Stars form within dense cores composed of both gas and dust within molecular clouds. However, despite the crucial role that dust plays in the star formation process, its dynamics is frequently overlooked, with the common assumption being a constant, spatially uniform dust-to-gas ratio and grain size spectrum. In this study, we introduce a set of radiation-dust-magnetohydrodynamic simulations of star-forming molecular clouds from the STARFORGE project. These simulations expand upon the earlier radiation MHD models, which included cooling, individual star formation, and feedback. Notably, they explicitly address the dynamics of dust grains, considering radiation, drag, and Lorentz forces acting on a diverse size spectrum of live dust grains. We find that once stars exceed a certain mass threshold (∼2 M\u2299), their emitted radiation can evacuate dust grains from their vicinity, giving rise to a dust-suppressed zone of size ∼100 au. This removal of dust, which interacts with gas through cooling, chemistry, drag, and radiative transfer, alters the gas properties in the region. Commencing during the early accretion stages and preceding the main-sequence phase, this process results in a mass-dependent depletion in the accreted dust-to-gas (ADG) mass ratio within both the circumstellar disk and the star. We predict that massive stars (\u227310 M\u2299) would exhibit ADG ratios that are approximately 1 order of magnitude lower than that of their parent clouds. Consequently, stars, their disks, and circumstellar environments would display notable deviations in the abundances of elements commonly associated with dust grains, such as carbon and oxygen.
\n
Abstract Feedback from supermassive black holes is believed to be a critical driver of the observed color bimodality of galaxies above the Milky Way mass scale. Active galactic nuclei (AGN) feedback has been modeled in many galaxy formation simulations, but most implementations have involved simplified prescriptions or a coarse-grained interstellar medium (ISM). We present the first set of Feedback In Realistic Environments (FIRE)-3 cosmological zoom-in simulations with AGN feedback evolved to z ∼ 0, examining the impact of AGN feedback on a set of galaxies with halos in the mass range 10¹²–10¹³ M\u2299. These simulations combine detailed stellar and ISM physics with multichannel AGN feedback including radiative feedback, mechanical outflows, and, in some simulations, cosmic rays (CRs). We find that massive (>L*) galaxies in these simulations can match local scaling relations including the stellar mass–halo mass relation and the M BH–σ relation; in the stronger model with CRs, they also match the size–mass relation and the Faber–Jackson relation. Many of the massive galaxies in the simulations with AGN feedback have quenched star formation and elliptical morphologies, in qualitative agreement with observations. In contrast, simulations at the massive end without AGN feedback produce galaxies that are too massive and form stars too rapidly, are order-of-magnitude too compact, and have velocity dispersions well above Faber–Jackson. Despite these successes, the AGN models analyzed do not produce uniformly realistic galaxies when the feedback parameters are held constant: While the stronger model produces the most realistic massive galaxies, it tends to overquench the lower-mass galaxies. This indicates that further refinements of the AGN modeling are needed.
",
"doi": "10.3847/1538-4357/ad67ca",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2024-10-01",
"series_number": "2",
"volume": "973",
"issue": "2",
"pages": "149"
},
{
"id": "authors:rcs8s-33478",
"collection": "authors",
"collection_id": "rcs8s-33478",
"cite_using_url": "https://authors.library.caltech.edu/records/rcs8s-33478",
"type": "article",
"title": "Playing with FIRE: A Galactic Feedback-halting Experiment Challenges Star Formation Rate Theories",
"author": [
{
"family_name": "Khullar",
"given_name": "Shivan",
"orcid": "0000-0003-1053-1262"
},
{
"family_name": "Matzner",
"given_name": "Christopher D.",
"orcid": "0000-0001-9732-2281"
},
{
"family_name": "Murray",
"given_name": "Norman",
"orcid": "0000-0002-8659-3729"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604"
},
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Stellar feedback influences the star formation rate (SFR) and the interstellar medium of galaxies in ways that are difficult to quantify numerically, because feedback is an essential ingredient of realistic simulations. To overcome this, we conduct a feedback-halting experiment starting with a Milky Way–mass galaxy in the second-generation Feedback In Realistic Environments (FIRE-2) simulation framework. By terminating feedback, and comparing to a simulation in which feedback is maintained, we monitor how the runs diverge. We find that without feedback, the interstellar turbulent velocities decay. There is a marked increase of dense material, while the SFR increases by over an order of magnitude. Importantly, this SFR boost is a factor of ∼15–20 larger than is accounted for by the increased freefall rate caused by higher densities. This implies that feedback moderates the star formation efficiency per freefall time more directly than simply through the density distribution. To probe changes at the scale of giant molecular clouds (GMCs), we identify GMCs using density and virial parameter thresholds, tracking clouds as the galaxy evolves. Halting feedback stimulates rapid changes, including a proliferation of new bound clouds, a decrease of turbulent support in loosely bound clouds, an overall increase in cloud densities, and a surge of internal star formation. Computing the cloud-integrated SFR using several theories of turbulence regulation, we show that these theories underpredict the surge in SFR by at least a factor of 3. We conclude that galactic star formation is essentially feedback regulated on scales that include GMCs, and that stellar feedback affects GMCs in multiple ways.
",
"doi": "10.3847/1538-4357/ad6311",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2024-09-20",
"series_number": "1",
"volume": "973",
"issue": "1",
"pages": "40"
},
{
"id": "authors:dnz9e-saw51",
"collection": "authors",
"collection_id": "dnz9e-saw51",
"cite_using_url": "https://authors.library.caltech.edu/records/dnz9e-saw51",
"type": "article",
"title": "Suppressed Cosmic-Ray Energy Densities in Molecular Clouds from Streaming Instability-regulated Transport",
"author": [
{
"family_name": "Fitz Axen",
"given_name": "Margot",
"orcid": "0000-0001-7220-5193"
},
{
"family_name": "Offner",
"given_name": "Stella",
"orcid": "0000-0003-1252-9916"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Krumholz",
"given_name": "Mark R.",
"orcid": "0000-0003-3893-854X"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604"
}
],
"abstract": "\n
Cosmic rays (CRs) are the primary driver of ionization in star-forming molecular clouds (MCs). Despite their potential impacts on gas dynamics and chemistry, no simulations of star cluster formation following the creation of individual stars have included explicit cosmic-ray transport (CRT) to date. We conduct the first numerical simulations following the collapse of a 2000M\u2299 MC and the subsequent star formation including CRT using the STAR FORmation in Gaseous Environments framework implemented in the GIZMO code. We show that when CRT is streaming-dominated, the CR energy in the cloud is strongly attenuated due to energy losses from the streaming instability. Consequently, in a Milky Way–like environment the median CR ionization rate in the cloud is low (ζ \u2272 2 × 10−19 s−1) during the main star-forming epoch of the calculation and the impact of CRs on the star formation in the cloud is limited. However, in high-CR environments, the CR distribution in the cloud is elevated (ζ \u2272 6 × 10−18), and the relatively higher CR pressure outside the cloud causes slightly earlier cloud collapse and increases the star formation efficiency by 50% to ∼13%. The initial mass function is similar in all cases except with possible variations in a high-CR environment. Further studies are needed to explain the range of ionization rates observed in MCs and explore star formation in extreme CR environments.
\n
Fuelling star formation in large, discy galaxies requires a continuous supply of gas accreting into star-forming regions. Previously, we characterized this accretion in four Milky Way mass galaxies ($M_{\\rm halo}\\sim 10^{12}{\\rm M}_{\\odot }$) in the FIRE-2 cosmological zoom-in simulations. At $z\\sim 0$, we found that gas within the inner circumgalactic medium (iCGM) approaches the disc with comparable angular momentum (AM) to the disc edge, joining in the outer half of the gaseous disc. Within the disc, gas moves inwards at velocities of $\\sim$1–5 km s$^{-1}$ while fully rotationally supported. In this study, we analyse the torques that drive these flows. In all cases studied, we find that the torques in discs enable gas accreted near the disc edge to transport inwards and fuel star formation in the central few kpc. The primary sources of torque come from gravity, hydrodynamical forces, and the sub-grid $P \\mathrm{ d}V$ work done by supernova (SN) remnants interacting with gas on $\\lesssim$10 pc scales. These SNe remnant interactions induce negative torques within the inner disc and positive torques in the outer disc. The gas–gas gravitational, hydro, and 'feedback' torques transfer AM outwards to where accreting gas joins the disc, playing an important role in driving inflows and regulating disc structure. Gravitational torques from stars and dark matter provide an AM sink within the innermost regions of the disc and iCGM, respectively. Feedback torques are dominant within the disc, while gravitational and hydrodynamical torques have similar significance depending on the system/region. Torques from viscous shearing, magnetic forces, stellar winds, and radiative transfer are less significant.
",
"doi": "10.1093/mnras/stae2021",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-09",
"series_number": "3",
"volume": "533",
"issue": "3",
"pages": "3008-3026"
},
{
"id": "authors:k9vgv-wha12",
"collection": "authors",
"collection_id": "k9vgv-wha12",
"cite_using_url": "https://authors.library.caltech.edu/records/k9vgv-wha12",
"type": "article",
"title": "The First Evidence of a Host Star Metallicity Cutoff in the Formation of Super-Earth Planets",
"author": [
{
"family_name": "Boley",
"given_name": "Kiersten M.",
"orcid": "0000-0001-8153-639X"
},
{
"family_name": "Christiansen",
"given_name": "Jessie L.",
"orcid": "0000-0002-8035-4778",
"clpid": "Christiansen-Jessie-L"
},
{
"family_name": "Zink",
"given_name": "Jon",
"orcid": "0000-0003-1848-2063",
"clpid": "Zink-Jon"
},
{
"family_name": "Hardegree-Ullman",
"given_name": "Kevin",
"orcid": "0000-0003-3702-0382"
},
{
"family_name": "Lee",
"given_name": "Eve J.",
"orcid": "0000-0002-1228-9820"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wang \u738b",
"given_name": "Ji \u5409",
"orcid": "0000-0002-4361-8885"
},
{
"family_name": "Fernandes",
"given_name": "Rachel B.",
"orcid": "0000-0002-3853-7327"
},
{
"family_name": "Bergsten",
"given_name": "Galen J.",
"orcid": "0000-0003-4500-8850"
},
{
"family_name": "Bhure",
"given_name": "Sakhee",
"orcid": "0000-0002-6673-8206"
}
],
"abstract": "Planet formation is expected to be severely limited in disks of low metallicity, owing to both the small solid mass reservoir and the low-opacity accelerating the disk gas dissipation. While previous studies have found a weak correlation between the occurrence rates of small planets (\u22724R ⊕) and stellar metallicity, so far no studies have probed below the metallicity limit beyond which planet formation is predicted to be suppressed. Here, we constructed a large catalog of ∼110,000 metal-poor stars observed by the TESS mission with spectroscopically derived metallicities, and systematically probed planet formation within the metal-poor regime ([Fe/H] ≤−0.5) for the first time. Extrapolating known higher-metallicity trends for small, short-period planets predicts the discovery of ∼68 super-Earths around these stars (∼85,000 stars) after accounting for survey completeness; however, we detect none. As a result, we have placed the most stringent upper limit on super-Earth occurrence rates around metal-poor stars (−0.75 < [Fe/H] ≤ −0.5) to date, ≤ 1.67%, a statistically significant (p-value = 0.000685) deviation from the prediction of metallicity trends derived with Kepler and K2. We find a clear host star metallicity cliff for super-Earths that could indicate the threshold below which planets are unable to grow beyond an Earth-mass at short orbital periods. This finding provides a crucial input to planet-formation theories, and has implications for the small planet inventory of the Galaxy and the galactic epoch at which the formation of small planets started.
",
"doi": "10.3847/1538-3881/ad6570",
"issn": "0004-6256",
"publisher": "American Astronomical Society",
"publication": "Astronomical Journal",
"publication_date": "2024-09",
"series_number": "3",
"volume": "168",
"issue": "3",
"pages": "128"
},
{
"id": "authors:8y89b-d6z44",
"collection": "authors",
"collection_id": "8y89b-d6z44",
"cite_using_url": "https://authors.library.caltech.edu/records/8y89b-d6z44",
"type": "article",
"title": "Unravelling jet quenching criteria across L* galaxies and massive cluster ellipticals",
"author": [
{
"family_name": "Su",
"given_name": "Kung-Yi",
"orcid": "0000-0003-1598-0083"
},
{
"family_name": "Bryan",
"given_name": "Greg L",
"orcid": "0000-0003-2630-9228"
},
{
"family_name": "Hayward",
"given_name": "Christopher C",
"orcid": "0000-0003-4073-3236"
},
{
"family_name": "Somerville",
"given_name": "Rachel S"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Emami",
"given_name": "Razieh",
"orcid": "0000-0002-2791-5011"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044"
},
{
"family_name": "Ponnada",
"given_name": "Sam B",
"orcid": "0000-0002-7484-2695",
"clpid": "Ponnada-Sam-B"
},
{
"family_name": "Fielding",
"given_name": "Drummond",
"orcid": "0000-0003-3806-8548"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067"
}
],
"abstract": "In the absence of supplementary heat, the radiative cooling of halo gas around massive galaxies (Milky Way mass and above) leads to an excess of cold gas or stars beyond observed levels. Active galactic nucleus jet-induced heating is likely essential, but the specific properties of the jets remain unclear. Our previous work concludes from simulations of a halo with $10^{14} \\,\\mathrm{ M}_\\odot$ that a successful jet model should have an energy flux comparable to the free-fall energy flux at the cooling radius and should inflate a sufficiently wide cocoon with a long enough cooling time. In this paper, we investigate three jet modes with constant fluxes satisfying the criteria, including high-temperature thermal jets, cosmic ray (CR)-dominant jets, and widely precessing kinetic jets in $10^{12}-10^{15}\\, {\\rm M}_{\\odot }$ haloes using high-resolution, non-cosmological magnetohydrodynamic simulations with the FIRE-2 (Feedback In Realistic Environments) stellar feedback model, conduction, and viscosity. We find that scaling the jet energy according to the free-fall energy at the cooling radius can successfully suppress the cooling flows and quench galaxies without violating observational constraints. On the contrary, if we scale the energy flux based on the total cooling rate within the cooling radius, strong interstellar medium cooling dominates this scaling, resulting in a jet flux exceeding what is needed. Among the three jet types, the CR-dominant jet is most effective in suppressing cooling flows across all surveyed halo masses due to enhanced CR pressure support. We confirm that the criteria for a successful jet model work across a wider range, encompassing halo masses of $10^{12}-10^{15} {\\rm M_\\odot }$.
",
"doi": "10.1093/mnras/stae1629",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-08",
"series_number": "2",
"volume": "532",
"issue": "2",
"pages": "2724-2740"
},
{
"id": "authors:w4956-00s63",
"collection": "authors",
"collection_id": "w4956-00s63",
"cite_using_url": "https://authors.library.caltech.edu/records/w4956-00s63",
"type": "article",
"title": "From Seeds to Supermassive Black Holes: Capture, Growth, Migration, and Pairing in Dense Protobulge Environments",
"author": [
{
"family_name": "Shi",
"given_name": "Yanlong",
"orcid": "0000-0002-0087-3237",
"clpid": "Shi-Yanlong"
},
{
"family_name": "Kremer",
"given_name": "Kyle",
"orcid": "0000-0002-4086-3180",
"clpid": "Kremer-Kyle"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "\n
The origins and mergers of supermassive black holes (SMBHs) remain a mystery. We describe a scenario from a novel multiphysics simulation featuring rapid (\u22721 Myr) hyper-Eddington gas capture by a ∼1000 M\u2299 \"seed\" black hole (BH) up to supermassive (\u2273106M\u2299) masses in a massive, dense molecular cloud complex typical of high-redshift starbursts. Due to the high cloud density, stellar feedback is inefficient, and most of the gas turns into stars in star clusters that rapidly merge hierarchically, creating deep potential wells. Relatively low-mass BH seeds at random positions can be \"captured\" by merging subclusters and migrate to the center in ∼1 freefall time (vastly faster than dynamical friction). This also efficiently produces a paired BH binary with ∼0.1 pc separation. The centrally concentrated stellar density profile (akin to a \"protobulge\") allows the cluster as a whole to capture and retain gas and build up a large (parsec-scale) circumbinary accretion disk with gas coherently funneled to the central BH (even when the BH radius of influence is small). The disk is \"hypermagnetized\" and \"flux-frozen\": dominated by a toroidal magnetic field with plasma β ∼ 10−3, with the fields amplified by flux-freezing. This drives hyper-Eddington inflow rates \u22731 M\u2299 yr−1, which also drive the two BHs to nearly equal masses. The late-stage system appears remarkably similar to recently observed high-redshift \"little red dots.\" This scenario can provide an explanation for rapid SMBH formation, growth, and mergers in high-redshift galaxies.
\n
The observationally inferred size versus stellar–mass relationship (SMR) for low-mass galaxies provides an important test for galaxy formation models. However, the relationship relies on assumptions that relate observed luminosity profiles to underlying stellar mass profiles. Here we use the Feedback in Realistic Environments simulations of low-mass galaxies to explore how the predicted SMR changes depending on whether one uses star-particle counts directly or mock observations. We reproduce the SMR found in The Exploration of Local Volume Satellites survey remarkably well only when we infer stellar masses and sizes using mock observations. However, when we use star particles to directly infer stellar masses and half-mass radii, we find that our galaxies are too large and obey an SMR with too little scatter compared to observations. This discrepancy between the 'true' galaxy size and mass and those derived in the mock observation approach is twofold. First, our simulated galaxies have higher and more varied mass-to-light ratios (MLR) at a fixed colour than those commonly adopted, which tends to underestimate their stellar masses compared to their true, simulated values. Second, our galaxies have radially increasing MLR gradients therefore using a single MLR tends to underpredict the mass in the outer regions. Similarly, the true half-mass radius is larger than the half-light radius because the light is more concentrated than the mass. If our simulations are accurate representations of the real Universe, then the relationship between galaxy size and stellar mass is even tighter for low-mass galaxies than is commonly inferred from observed relations.
",
"doi": "10.1093/mnras/stae1505",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-07",
"series_number": "1",
"volume": "532",
"issue": "1",
"pages": "538-548"
},
{
"id": "authors:dp84q-vvv86",
"collection": "authors",
"collection_id": "dp84q-vvv86",
"cite_using_url": "https://authors.library.caltech.edu/records/dp84q-vvv86",
"type": "article",
"title": "TRINITY IV: predictions for supermassive black holes at z \u2273 6",
"author": [
{
"family_name": "Zhang",
"given_name": "Haowen",
"orcid": "0000-0002-4321-3538"
},
{
"family_name": "Behroozi",
"given_name": "Peter",
"orcid": "0000-0002-2517-6446"
},
{
"family_name": "Volonteri",
"given_name": "Marta",
"orcid": "0000-0002-3216-1322"
},
{
"family_name": "Silk",
"given_name": "Joseph",
"orcid": "0000-0002-1566-8148"
},
{
"family_name": "Fan",
"given_name": "Xiaohui",
"orcid": "0000-0003-3310-0131"
},
{
"family_name": "Aird",
"given_name": "James",
"orcid": "0000-0003-1908-8463"
},
{
"family_name": "Yang",
"given_name": "Jinyi",
"orcid": "0000-0001-5287-4242"
},
{
"family_name": "Wang",
"given_name": "Feige",
"orcid": "0000-0002-0210-7499"
},
{
"family_name": "Tee",
"given_name": "Wei Leong",
"orcid": "0000-0003-0747-1780"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We present predictions for the high-redshift halo–galaxy–supermassive black hole (SMBH) connection from the Trinity model. Matching a comprehensive compilation of galaxy (0 ≤ z ≤ 13) and SMBH data sets (0 ≤ z ≤ 6.5), Trinity finds: (1) The number of SMBHs with M• > 109 M\u2299 in the observable Universe increases by five orders of magnitude from z ∼ 10 to z ∼ 2, and by another factor of ∼3 from z ∼ 2 to z = 0; (2) The M• > 109 and 1010 M\u2299 SMBHs at z ∼ 6 live in haloes with ∼(2 − 3) and (3 − 5) × 1012 M\u2299; (3) the newly discovered JWST AGN candidates at 7 \u2272 z \u2272 11 are overmassive compared to the intrinsic SMBH mass–galaxy mass relation from Trinity, but they are still broadly consistent with Trinity predictions for flux limited AGN samples with Lauer bias. This bias favours the detection for overmassive SMBHs due to higher luminosities at a fixed Eddington ratio. However UHZ1’s M•/M* ratio is still some 1 dex higher than Trinity AGNs, indicating a discrepancy; (4) Trinity underpredicts the number densities of GN-z11 and CEERS_1019 analogues. But given the strong constraints from existing data in Trinity, the extra constraint from GN-z11 and CEERS_1019 does not significantly change trinity model results. (5) z = 6–10 quasar luminosity functions will reduce uncertainties in the trinity prediction of the z = 6–10 SMBH mass–galaxy mass relation by up to ∼0.5 dex. These luminosity functions will be available with future telescopes, such as Roman and Euclid.
",
"doi": "10.1093/mnras/stae1447",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-07",
"series_number": "4",
"volume": "531",
"issue": "4",
"pages": "4974-4989"
},
{
"id": "authors:dtqr4-evn33",
"collection": "authors",
"collection_id": "dtqr4-evn33",
"cite_using_url": "https://authors.library.caltech.edu/records/dtqr4-evn33",
"type": "article",
"title": "H\u2009I discs of L* galaxies as probes of the baryonic physics of galaxy evolution",
"author": [
{
"family_name": "Gensior",
"given_name": "Jindra",
"orcid": "0000-0001-6119-9883"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919"
},
{
"family_name": "Reina-Campos",
"given_name": "Marta",
"orcid": "0000-0002-8556-4280"
},
{
"family_name": "Trujillo-Gomez",
"given_name": "Sebastian",
"orcid": "0000-0003-2482-0049"
},
{
"family_name": "Mayer",
"given_name": "Lucio",
"orcid": "0000-0002-7078-2074"
},
{
"family_name": "Keller",
"given_name": "Benjamin W",
"orcid": "0000-0002-9642-7193"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942"
},
{
"family_name": "Kruijssen",
"given_name": "J M Diederik",
"orcid": "0000-0002-8804-0212"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232"
}
],
"abstract": "Understanding what shapes the cold gas component of galaxies, which both provides the fuel for star formation and is strongly affected by the subsequent stellar feedback, is a crucial step towards a better understanding of galaxy evolution. Here, we analyse the H i properties of a sample of 46 Milky Way halo-mass galaxies, drawn from cosmological simulations (EMP-Pathfinder and Firebox). This set of simulations comprises galaxies evolved self-consistently across cosmic time with different baryonic sub-grid physics: three different star formation models [constant star formation efficiency (SFE) with different star formation eligibility criteria, and an environmentally dependent, turbulence-based SFE] and two different feedback prescriptions, where only one sub-sample includes early stellar feedback. We use these simulations to assess the impact of different baryonic physics on the H i content of galaxies. We find that the galaxy-wide H i properties agree with each other and with observations. However, differences appear for small-scale properties. The thin H i discs observed in the local universe are only reproduced with a turbulence-dependent SFE and/or early stellar feedback. Furthermore, we find that the morphology of H i discs is particularly sensitive to the different physics models: galaxies simulated with a turbulence-based SFE have discs that are smoother and more rotationally symmetric, compared to those simulated with a constant SFE; galaxies simulated with early stellar feedback have more regular discs than supernova-feedback-only galaxies. We find that the rotational asymmetry of the H i discs depends most strongly on the underlying physics model, making this a promising observable for understanding the physics responsible for shaping the interstellar medium of galaxies.
",
"doi": "10.1093/mnras/stae1217",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-06",
"series_number": "1",
"volume": "531",
"issue": "1",
"pages": "1158-1178"
},
{
"id": "authors:s2egk-9a002",
"collection": "authors",
"collection_id": "s2egk-9a002",
"cite_using_url": "https://authors.library.caltech.edu/records/s2egk-9a002",
"type": "article",
"title": "Dissipative Dark Substructure: The Consequences of Atomic Dark Matter on Milky Way Analog Subhalos",
"author": [
{
"family_name": "Gemmell",
"given_name": "Caleb",
"orcid": "0000-0002-6505-8559",
"clpid": "Gemmell-Caleb"
},
{
"family_name": "Roy",
"given_name": "Sandip",
"orcid": "0000-0002-7638-7454",
"clpid": "Roy-Sandip"
},
{
"family_name": "Shen",
"given_name": "Xuejian",
"orcid": "0000-0002-6196-823X",
"clpid": "Shen-Xuejian"
},
{
"family_name": "Curtin",
"given_name": "David",
"orcid": "0000-0003-0263-6195",
"clpid": "Curtin-David"
},
{
"family_name": "Lisanti",
"given_name": "Mariangela",
"orcid": "0000-0002-8495-8659",
"clpid": "Lisanti-Mariangela"
},
{
"family_name": "Murray",
"given_name": "Norman",
"orcid": "0000-0002-8659-3729",
"clpid": "Murray-Norman"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "\n
Using cosmological hydrodynamical zoom-in simulations, we explore the properties of subhalos in Milky Way analogs that contain a subcomponent of atomic dark matter (ADM). ADM differs from cold dark matter (CDM) due to the presence of self-interactions that lead to energy dissipation, analogous to standard model baryons. This model can arise in dark sectors that are natural and theoretically motivated extensions to the standard model. The simulations used in this work were carried out using GIZMO and utilize the FIRE-2 galaxy formation physics in the standard model baryonic sector. For the parameter points we consider, the ADM gas cools efficiently, allowing it to collapse to the center of subhalos. This increases a subhalo's central density and affects its orbit, with more subhalos surviving small pericentric passages. The subset of subhalos that host satellite galaxies have cuspier density profiles and smaller stellar half-mass radii relative to CDM. The entire population of dwarf galaxies produced in the ADM simulations is more compact than those seen in CDM simulations, unable to reproduce the entire diversity of observed dwarf galaxy structures. Additionally, we also identify a population of highly compact subhalos that consist nearly entirely of ADM and form in the central region of the host, where they can leave distinctive imprints in the baryonic disk. This work presents the first detailed exploration of subhalo properties in a strongly dissipative dark matter scenario, providing intuition for how other regions of ADM parameter space, as well as other dark sector models, would impact galactic-scale observables.
\n
\n
We analyze the first cosmological baryonic zoom-in simulations of galaxies in dissipative self-interacting dark matter (dSIDM). The simulations utilize the FIRE-2 galaxy formation physics with the inclusion of dissipative dark matter self-interactions modeled as a constant fractional energy dissipation (fdiss = 0.75). In this paper, we examine the properties of dwarf galaxies with M* ∼ 105–109M\u2299 in both isolation and within Milky Way–mass hosts. For isolated dwarfs, we find more compact galaxy sizes and promotion of disk formation in dSIDM with (σ/m) ≤ 1 cm2 g−1. On the contrary, models with (σ/m) = 10 cm2 g−1 produce puffier stellar distributions that are in tension with the observed size–mass relation. In addition, owing to the steeper central density profiles, the subkiloparsec circular velocities of isolated dwarfs when (σ/m) ≥ 0.1 cm2 g−1 are enhanced by about a factor of 2, which are still consistent with the kinematic measurements of Local Group dwarfs but in tension with the H i rotation curves of more massive field dwarfs. Meanwhile, for satellites of Milky Way–mass hosts, the median circular velocity profiles are marginally affected by dSIDM physics, but dSIDM may help promote the structural diversity of dwarf satellites. The number of satellites is slightly enhanced in dSIDM, but the differences are small compared with the large host-to-host variations. In conclusion, the dSIDM models with (σ/m) \u2273 0.1 cm2 g−1, fdiss = 0.75 are in tension in massive dwarfs (Mhalo ∼ 1011M\u2299) due to circular velocity constraints. However, models with lower effective cross sections (at this halo mass/velocity scale) are still viable and can produce nontrivial observable signatures.
\n
We investigate the formation of dense stellar clumps in a suite of high-resolution cosmological zoom-in simulations of a massive, star-forming galaxy at z ∼ 2 under the presence of strong quasar winds. Our simulations include multiphase ISM physics from the Feedback In Realistic Environments (FIRE) project and a novel implementation of hyper-refined accretion disc winds. We show that powerful quasar winds can have a global negative impact on galaxy growth while in the strongest cases triggering the formation of an off-centre clump with stellar mass ${\\rm M}_{\\star }\\sim 10^{7}\\, {\\rm M}_{\\odot }$, effective radius ${\\rm R}_{\\rm 1/2\\, \\rm Clump}\\sim 20\\, {\\rm pc}$, and surface density $\\Sigma _{\\star } \\sim 10^{4}\\, {\\rm M}_{\\odot }\\, {\\rm pc}^{-2}$. The clump progenitor gas cloud is originally not star-forming, but strong ram pressure gradients driven by the quasar winds (orders of magnitude stronger than experienced in the absence of winds) lead to rapid compression and subsequent conversion of gas into stars at densities much higher than the average density of star-forming gas. The AGN-triggered star-forming clump reaches ${\\rm SFR} \\sim 50\\, {\\rm M}_{\\odot }\\, {\\rm yr}^{-1}$ and $\\Sigma _{\\rm SFR} \\sim 10^{4}\\, {\\rm M}_{\\odot }\\, {\\rm yr}^{-1}\\, {\\rm kpc}^{-2}$, converting most of the progenitor gas cloud into stars in ∼2 Myr, significantly faster than its initial free-fall time and with stellar feedback unable to stop star formation. In contrast, the same gas cloud in the absence of quasar winds forms stars over a much longer period of time (∼35 Myr), at lower densities, and losing spatial coherency. The presence of young, ultra-dense, gravitationally bound stellar clumps in recently quenched galaxies could thus indicate local positive feedback acting alongside the strong negative impact of powerful quasar winds, providing a plausible formation scenario for globular clusters.
",
"doi": "10.1093/mnras/stae1021",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-05",
"series_number": "3",
"volume": "530",
"issue": "3",
"pages": "2795-2809"
},
{
"id": "authors:sb9kz-se967",
"collection": "authors",
"collection_id": "sb9kz-se967",
"cite_using_url": "https://authors.library.caltech.edu/records/sb9kz-se967",
"type": "article",
"title": "Synchrotron signatures of cosmic ray transport physics in galaxies",
"author": [
{
"family_name": "Ponnada",
"given_name": "Sam B",
"orcid": "0000-0002-7484-2695",
"clpid": "Ponnada-Sam-B"
},
{
"family_name": "Butsky",
"given_name": "Iryna S",
"orcid": "0000-0003-1257-5007",
"clpid": "Butsky-Iryna-S"
},
{
"family_name": "Skalidis",
"given_name": "Raphael",
"orcid": "0000-0003-2337-0277",
"clpid": "Skalidis-Raphael"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Panopoulou",
"given_name": "Georgia V",
"orcid": "0000-0001-7482-5759"
},
{
"family_name": "Hummels",
"given_name": "Cameron",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628"
},
{
"family_name": "Su",
"given_name": "Kung-Yi",
"orcid": "0000-0003-1598-0083"
}
],
"abstract": "Cosmic rays (CRs) may drive outflows and alter the phase structure of the circumgalactic medium, with potentially important implications on galaxy formation. However, these effects ultimately depend on the dominant mode of transport of CRs within and around galaxies, which remains highly uncertain. To explore potential observable constraints on CR transport, we investigate a set of cosmological fire-2 CR-magnetohydrodynamic simulations of L* galaxies which evolve CRs with transport models motivated by self-confinement (SC) and extrinsic turbulence (ET) paradigms. To first order, the synchrotron properties diverge between SC and ET models due to a CR physics-driven hysteresis. SC models show a higher tendency to undergo 'ejective' feedback events due to a runaway buildup of CR pressure in dense gas due to the behaviour of SC transport scalings at extremal CR energy densities. The corresponding CR wind-driven hysteresis results in brighter, smoother, and more extended synchrotron emission in SC runs relative to ET and constant diffusion runs. The differences in synchrotron arise from different morphology, interstellar medium gas, and B properties, potentially ruling out SC as the dominant mode of CR transport in typical star-forming L* galaxies, and indicating the prospect for non-thermal radio continuum observations to constrain CR transport physics.
",
"doi": "10.1093/mnrasl/slae017",
"issn": "1745-3925",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society: Letters",
"publication_date": "2024-05",
"series_number": "1",
"volume": "530",
"issue": "1",
"pages": "L1-L6"
},
{
"id": "authors:vs2cx-cwe52",
"collection": "authors",
"collection_id": "vs2cx-cwe52",
"cite_using_url": "https://authors.library.caltech.edu/records/vs2cx-cwe52",
"type": "article",
"title": "Hooks\u00a0& Bends in the radial acceleration relation: discriminatory tests for dark matter and MOND",
"author": [
{
"family_name": "Mercado",
"given_name": "Francisco J",
"orcid": "0000-0002-5908-737X",
"clpid": "Mercado-Francisco-J"
},
{
"family_name": "Bullock",
"given_name": "James S",
"orcid": "0000-0003-4298-5082"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628"
},
{
"family_name": "Samuel",
"given_name": "Jenna",
"orcid": "0000-0002-8429-4100"
}
],
"abstract": "The radial acceleration relation (RAR) connects the total gravitational acceleration of a galaxy at a given radius, atot(r), with that accounted for by baryons at the same radius, abar(r). The shape and tightness of the RAR for rotationally-supported galaxies have characteristics in line with MOdified Newtonian Dynamics (MOND) and can also arise within the cosmological constant + cold dark matter (ΛCDM) paradigm. We use zoom simulations of 20 galaxies with stellar masses of M\u22c6 \u2243 107–11 M\u2299 to study the RAR in the FIRE-2 simulations. We highlight the existence of simulated galaxies with non-monotonic RAR tracks that ‘hook’ down from the average relation. These hooks are challenging to explain in Modified Inertia theories of MOND, but naturally arise in all of our ΛCDM-simulated galaxies that are dark-matter dominated at small radii and have feedback-induced cores in their dark matter haloes. We show, analytically and numerically, that downward hooks are expected in such cored haloes because they have non-monotonic acceleration profiles. We also extend the relation to accelerations below those traced by disc galaxy rotation curves. In this regime, our simulations exhibit ‘bends’ off of the MOND-inspired extrapolation of the RAR, which, at large radii, approach atot ≈ abar/fb, where fb is the cosmic baryon fraction. Future efforts to search for these hooks and bends in real galaxies will provide interesting tests for MOND and ΛCDM.
",
"doi": "10.1093/mnras/stae819",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-05",
"series_number": "2",
"volume": "530",
"issue": "2",
"pages": "1349-1362"
},
{
"id": "authors:3j95j-ts208",
"collection": "authors",
"collection_id": "3j95j-ts208",
"cite_using_url": "https://authors.library.caltech.edu/records/3j95j-ts208",
"type": "article",
"title": "TRINITY \u2013 III. Quasar luminosity functions decomposed by halo, galaxy, and black hole masses as well as Eddington ratios from z = 0\u201310",
"author": [
{
"family_name": "Zhang",
"given_name": "Haowen",
"orcid": "0000-0002-4321-3538"
},
{
"family_name": "Behroozi",
"given_name": "Peter",
"orcid": "0000-0002-2517-6446"
},
{
"family_name": "Volonteri",
"given_name": "Marta",
"orcid": "0000-0002-3216-1322"
},
{
"family_name": "Silk",
"given_name": "Joseph",
"orcid": "0000-0002-1566-8148"
},
{
"family_name": "Fan",
"given_name": "Xiaohui",
"orcid": "0000-0003-3310-0131"
},
{
"family_name": "Aird",
"given_name": "James",
"orcid": "0000-0003-1908-8463"
},
{
"family_name": "Yang",
"given_name": "Jinyi",
"orcid": "0000-0001-5287-4242"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We present the redshift evolution of quasar luminosity functions (QLFs) decomposed by halo mass, galaxy mass, supermassive black hole (SMBH) mass, and Eddington ratio, as well as SMBH/radiative energy output ratios from trinity, a flexible empirical model that self-consistently infers the halo–galaxy–SMBH connection that match observational data. Key findings include: (1) The normalization of quasar luminosity function increases by ∼3–4 dex from z ∼ 10 to z ∼ 4, due to the fast mass build-up of different SMBH populations; (2) From z ∼ 4 to z ∼ 1, less massive galaxies and SMBHs make up bigger and bigger fractions of QLFs, due to the active galactic nuclei (AGNs) downsizing effect; (3) At z ∼ 0, massive haloes/galaxies/SMBHs are responsible for most bright quasars due to low Eddington ratios among all SMBHs; (4) The bright ends of QLFs are dominated by SMBHs that are at least 0.3 dex overmassive relative to the median SMBH mass–galaxy mass relation; (5) QLFs at z ∼ 6–7 are dominated by SMBHs accreting at Eddington ratios 0.1 < ηrad < 1, but super-Eddington AGNs contribute more significantly to QLFs towards z ∼ 9–10.
",
"doi": "10.1093/mnras/stae655",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-04",
"series_number": "3",
"volume": "529",
"issue": "3",
"pages": "2777-2793"
},
{
"id": "authors:qf19h-9rs80",
"collection": "authors",
"collection_id": "qf19h-9rs80",
"cite_using_url": "https://authors.library.caltech.edu/records/qf19h-9rs80",
"type": "article",
"title": "A Dusty Locale: evolution of galactic dust populations from Milky Way to dwarf-mass galaxies",
"author": [
{
"family_name": "Choban",
"given_name": "Caleb R",
"orcid": "0000-0001-9200-169X"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067"
},
{
"family_name": "Sandstrom",
"given_name": "Karin M",
"orcid": "0000-0002-4378-8534"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hayward",
"given_name": "Christopher C",
"orcid": "0000-0003-4073-3236"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628"
}
],
"abstract": "Observations indicate dust populations vary between galaxies and within them, suggesting a complex life cycle and evolutionary history. Here we investigate the evolution of galactic dust populations across cosmic time using a suite of cosmological zoom-in simulations from the Feedback in Realistic Environments project, spanning $M_{\\rm vir}=10^{9-12}{M}_{\\odot };\\, M_{*}=10^{6-11}\\, {M}_{\\odot }$. Our simulations incorporate a dust evolution model that accounts for the dominant sources of dust production, growth, and destruction and follows the evolution of specific dust species. All galactic dust populations in our suite exhibit similar evolutionary histories, with gas–dust accretion being the dominant producer of dust mass for all but the most metal-poor galaxies. Similar to previous works, we find the onset of efficient gas–dust accretion occurs above a 'critical' metallicity threshold (Zcrit). Due to this threshold, our simulations reproduce observed trends between galactic D/Z and metallicity and element depletion trends in the interstellar medium. However, we find Zcrit varies between dust species due to differences in key element abundances, dust physical properties, and life cycle processes resulting in $Z_{\\rm crit}\\sim 0.05{\\rm Z}_{\\odot },\\, 0.2{\\rm Z}_{\\odot },\\, 0.5{\\rm Z}_{\\odot }$ for metallic iron, silicates, and carbonaceous dust, respectively. These variations could explain the lack of small carbonaceous grains observed in the Magellanic Clouds. We also find a delay between the onset of gas–dust accretion and when a dust population reaches equilibrium, which we call the equilibrium time-scale (τequil). The relation between τequil and the metal enrichment time-scale of a galaxy, determined by its recent evolutionary history, can contribute to the scatter in the observed relation between galactic D/Z and metallicity.
",
"doi": "10.1093/mnras/stae716",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-04",
"series_number": "3",
"volume": "529",
"issue": "3",
"pages": "2356-2378"
},
{
"id": "authors:tdfh4-wyq41",
"collection": "authors",
"collection_id": "tdfh4-wyq41",
"cite_using_url": "https://authors.library.caltech.edu/records/tdfh4-wyq41",
"type": "article",
"title": "Constrain the Dark-matter Distribution of Ultra-diffuse Galaxies with Globular-cluster Mass Segregation: A Case Study with NGC5846-UDG1",
"author": [
{
"family_name": "Liang",
"given_name": "Jinning",
"orcid": "0000-0001-8405-2921",
"clpid": "Liang-Jinning"
},
{
"family_name": "Jiang",
"given_name": "Fangzhou",
"orcid": "0000-0001-6115-0633",
"clpid": "Jiang-Fangzhou"
},
{
"family_name": "Danieli",
"given_name": "Shany",
"orcid": "0000-0002-1841-2252",
"clpid": "Danieli-Shany"
},
{
"family_name": "Benson",
"given_name": "Andrew",
"orcid": "0000-0001-5501-6008",
"clpid": "Benson-Andrew-J"
},
{
"family_name": "Hopkins",
"given_name": "Phil",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "\n
The properties of globular clusters (GCs) contain valuable information of their host galaxies and dark-matter halos. In the remarkable example of ultra-diffuse galaxy, NGC5846-UDG1, the GC population exhibits strong radial mass segregation, indicative of dynamical-friction-driven orbital decay, which opens the possibility of using imaging data alone to constrain the dark-matter content of the galaxy. To explore this possibility, we develop a semianalytical model of GC evolution, which starts from the initial mass, structural, and spatial distributions of the GC progenitors, and follows the effects of dynamical friction, tidal evolution, and two-body relaxation. Using Markov Chain Monte Carlo, we forward-model the GCs in a UDG1-like potential to match the observed GC statistics, and to constrain the profile of the host halo and the origin of the GCs. We find that, with the assumptions of zero mass segregation when the star clusters were born, UDG1 is relatively dark-matter-poor compared to what is expected from stellar-to-halo–mass relations, and its halo concentration is lower than the cosmological average, irrespective of having a cuspy or a cored profile. Its GC population has an initial spatial distribution more extended than the smooth stellar distribution. We discuss the results in the context of scaling laws of galaxy–halo connections, and warn against naively using the GC-abundance–halo–mass relation to infer the halo mass of ultra-diffuse galaxies. Our model is generally applicable to GC-rich dwarf galaxies, and is publicly available.
\n
It has recently become possible to zoom-in from cosmological to sub-pc scales in galaxy simulations to follow accretion onto supermassive black holes (SMBHs). However, at some point the approximations used on ISM scales (e.g. optically-thin cooling and stellar-population-integrated star formation [SF] and feedback [FB]) break down. We therefore present the first cosmological radiation-magnetohydrodynamic (RMHD) simulation which self-consistently combines the FIRE physics (relevant on galactic/ISM scales where SF/FB are ensemble-averaged) and STARFORGE physics (relevant on small scales where we track individual (proto)stellar formation and evolution), together with explicit RMHD (including non-ideal MHD and multi-band M1-RHD) which self-consistently treats both optically-thick and thin regimes. This allows us to span scales from ~100 Mpc down to <100 au (~300 Schwarzschild radii) around a SMBH at a time where it accretes as a bright quasar, in a single simulation. We show that accretion rates up to ∼10−100 M_\u2299 yr\u207b¹ can be sustained into the accretion disk at \u226a10³ \ud835\udc45_(schw), with gravitational torques between stars and gas dominating on sub-kpc scales until star formation is shut down on sub-pc scales by a combination of optical depth to cooling and strong magnetic fields. There is an intermediate-scale, flux-frozen disk which is gravitoturbulent and stabilized by magnetic pressure sustaining strong turbulence and inflow with persistent spiral modes. In this paper we focus on how gas gets into the small-scale disk, and how star formation is efficiently suppressed.
",
"doi": "10.21105/astro.2309.13115",
"issn": "2565-6120",
"publisher": "Maynooth University",
"publication": "Open Journal of Astrophysics",
"publication_date": "2024-03-14",
"volume": "7",
"pages": "astro.2309.13115"
},
{
"id": "authors:zd9c7-w1f29",
"collection": "authors",
"collection_id": "zd9c7-w1f29",
"cite_using_url": "https://authors.library.caltech.edu/records/zd9c7-w1f29",
"type": "article",
"title": "Galactic cosmic-ray scattering due to intermittent structures",
"author": [
{
"family_name": "Butsky",
"given_name": "Iryna S",
"orcid": "0000-0003-1257-5007",
"clpid": "Butsky-Iryna-S"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kempski",
"given_name": "Philipp",
"orcid": "0009-0009-2144-3912"
},
{
"family_name": "Ponnada",
"given_name": "Sam B",
"orcid": "0000-0002-7484-2695",
"clpid": "Ponnada-Sam-B"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X"
}
],
"abstract": "Cosmic rays (CRs) with energies \u226a TeV comprise a significant component of the interstellar medium (ISM). Major uncertainties in CR behaviour on observable scales (much larger than CR gyroradii) stem from how magnetic fluctuations scatter CRs in pitch angle. Traditional first-principles models, which assume these magnetic fluctuations are weak and uniformly scatter CRs in a homogeneous ISM, struggle to reproduce basic observables such as the dependence of CR residence times and scattering rates on rigidity. We therefore explore a new category of ‘patchy’ CR scattering models, wherein CRs are pre-dominantly scattered by intermittent strong scattering structures with small volume-filling factors. These models produce the observed rigidity dependence with a simple size distribution constraint, such that larger scattering structures are rarer but can scatter a wider range of CR energies. To reproduce the empirically inferred CR scattering rates, the mean free path between scattering structures must be \u2113_(mfp) ~ 10 pc at GeV energies. We derive constraints on the sizes, internal properties, mass/volume-filling factors, and the number density any such structures would need to be both physically and observationally consistent. We consider a range of candidate structures, both large scale (e.g. H ii regions) and small scale (e.g. intermittent turbulent structures, perhaps even associated with radio plasma scattering) and show that while many macroscopic candidates can be immediately ruled out as the primary CR scattering sites, many smaller structures remain viable and merit further theoretical study. We discuss future observational constraints that could test these models.
",
"doi": "10.1093/mnras/stae276",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-03",
"series_number": "3",
"volume": "528",
"issue": "3",
"pages": "4245-4254"
},
{
"id": "authors:d782n-c7c74",
"collection": "authors",
"collection_id": "d782n-c7c74",
"cite_using_url": "https://authors.library.caltech.edu/records/d782n-c7c74",
"type": "article",
"title": "Disruption of Dark Matter Minihalos in the Milky Way Environment: Implications for Axion Miniclusters and Early Matter Domination",
"author": [
{
"family_name": "Shen",
"given_name": "Xuejian",
"orcid": "0000-0002-6196-823X",
"clpid": "Shen-Xuejian"
},
{
"family_name": "Xiao",
"given_name": "Huangyu",
"orcid": "0000-0003-2485-5700",
"clpid": "Xiao-Huangyu"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Zurek",
"given_name": "Kathryn M.",
"orcid": "0000-0002-2629-337X",
"clpid": "Zurek-K-M"
}
],
"abstract": "\n
Many theories of dark matter beyond the weakly interacting massive particles paradigm feature an enhanced matter power spectrum on subparsec scales, leading to the formation of dense dark matter minihalos. Future local observations are promising to search for and constrain such substructures. The survival probability of these dense minihalos in the Milky Way environment is crucial for interpreting local observations. In this work, we investigate two environmental effects: stellar disruption and (smooth) tidal disruption. These two mechanisms are studied using semianalytic models and idealized N-body simulations. For stellar disruption, we perform a series of N-body simulations of isolated minihalo–star encounters to test and calibrate analytic models of stellar encounters before applying the model to the realistic Milky Way disk environment. For tidal disruption, we perform N-body simulations to confirm the effectiveness of the analytic treatment. Finally, we propose a framework to combine the hierarchical assembly and infall of minihalos to the Milky Way with the late-time disruption mechanisms. We make predictions for the mass functions of minihalos in the Milky Way. The mass survival fraction (at Mmh ≥ 10−12M\u2299) of dense dark matter minihalos, e.g., for axion miniclusters and minihalos from early matter domination, is ∼60% with the relatively low-mass, compact population surviving. The survival fraction is insensitive to the detailed model parameters. We discuss various implications of the framework and future direct detection prospects.
\n
Synchrotron emission is one of few observable tracers of galactic magnetic fields (B) and cosmic rays (CRs). Much of our understanding of B in galaxies comes from utilizing synchrotron observations in conjunction with several simplifying assumptions of equipartition models, however, it remains unclear how well these assumptions hold, and what B these estimates physically represent. Using Feedback in Realistic Environments project simulations which self-consistently evolve CR proton, electron, and positron spectra from MeV to TeV energies, we present the first synthetic synchrotron emission predictions from simulated L* galaxies with ‘live’ spectrally resolved CR-magnetohydrodynamic. We find that synchrotron emission can be dominated by relatively cool and dense gas, resulting in equipartition estimates of B with fiducial assumptions underestimating the ‘true’ B in the gas that contributes the most emission by factors of 2–3 due to small volume-filling factors. Motivated by our results, we present an analytical framework that expands upon equipartition models for estimating B in a multiphase medium. Comparing our spectrally resolved synchrotron predictions to simpler spectral assumptions used in galaxy simulations with CRs, we find that spectral evolution can be crucial for accurate synchrotron calculations towards galactic centres, where loss terms are large.
",
"doi": "10.1093/mnras/stad3978",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-02",
"series_number": "4",
"volume": "527",
"issue": "4",
"pages": "11707-11718"
},
{
"id": "authors:x9jtn-nhd36",
"collection": "authors",
"collection_id": "x9jtn-nhd36",
"cite_using_url": "https://authors.library.caltech.edu/records/x9jtn-nhd36",
"type": "article",
"title": "[C\u2009II] 158 \u03bcm emission as an indicator of galaxy star formation rate",
"author": [
{
"family_name": "Liang",
"given_name": "Lichen",
"orcid": "0000-0001-9422-0095"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919"
},
{
"family_name": "Murray",
"given_name": "Norman",
"orcid": "0000-0002-8659-3729"
},
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309"
},
{
"family_name": "Hayward",
"given_name": "Christopher C",
"orcid": "0000-0003-4073-3236"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945"
},
{
"family_name": "Bassini",
"given_name": "Luigi",
"orcid": "0000-0002-6864-7762"
},
{
"family_name": "Richings",
"given_name": "Alexander J",
"orcid": "0000-0003-0502-9235"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628"
},
{
"family_name": "Chung",
"given_name": "Dongwoo T",
"orcid": "0000-0003-2618-6504"
},
{
"family_name": "Chan",
"given_name": "Jennifer Y H",
"orcid": "0000-0003-0314-7027"
},
{
"family_name": "Tolgay",
"given_name": "Do\u01e7a",
"orcid": "0000-0002-3155-946X"
},
{
"family_name": "\u00c7atmabacak",
"given_name": "Onur",
"orcid": "0000-0003-4067-1434"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Observations of local star-forming galaxies (SFGs) show a tight correlation between their singly ionized carbon line luminosity (\u2060\u2060L[C II]) and star formation rate (SFR), suggesting that \u2060\u2060L[C II] may be a useful SFR tracer for galaxies. Some other galaxy populations, however, are found to have lower \u2060\u2060L[C II]/SFR than local SFGs, including the infrared (IR)-luminous, starburst galaxies at low and high redshifts as well as some moderately SFGs at the epoch of re-ionization (EoR). The origins of this ‘[C II] deficit’ is unclear. In this work, we study the L[C II]–SFR relation of galaxies using a sample of z = 0–8 galaxies with M* ≈ 10\u2077 - 5 x 10¹¹ M\u2299 extracted from cosmological volume and zoom-in simulations from the Feedback in Realistic Environments (fire) project. We find a simple analytic expression for L[C II]/SFR of galaxies in terms of the following parameters: mass fraction of [C II]-emitting gas (\u2060\u2060f[C II]), gas metallicity (Zgas), gas density (ngas), and gas depletion time (\u2060\u2060tdep = Mgas/SFR). We find two distinct physical regimes: H\u2082-rich galaxies, where tdep is the main driver of the [C II] deficit and H\u2082-poor galaxies where Zgas is the main driver. The observed [C II] deficit of IR-luminous galaxies and early EoR galaxies, corresponding to the two different regimes, is due to short gas depletion time and low gas metallicity, respectively. Our result indicates that the [C II] deficit is a common phenomenon of galaxies, and caution needs to be taken when applying a constant L[C II]-to-SFR conversion factor derived from local SFGs to estimate cosmic SFR density at high redshifts and interpret data from upcoming [C II] line intensity mapping experiments.
",
"doi": "10.1093/mnras/stad3792",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-02",
"series_number": "1",
"volume": "528",
"issue": "1",
"pages": "499-541"
},
{
"id": "authors:gzvzv-2dt73",
"collection": "authors",
"collection_id": "gzvzv-2dt73",
"cite_using_url": "https://authors.library.caltech.edu/records/gzvzv-2dt73",
"type": "article",
"title": "Disc settling and dynamical heating: histories of Milky Way-mass stellar discs across cosmic time in the FIRE simulations",
"author": [
{
"family_name": "McCluskey",
"given_name": "Fiona"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942"
},
{
"family_name": "Loebman",
"given_name": "Sarah R",
"orcid": "0000-0003-3217-5967"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We study the kinematics of stars both at their formation and today within 14 Milky Way (MW)-mass galaxies from the FIRE-2 cosmological zoom-in simulations. We quantify the relative importance of cosmological disc settling and post-formation dynamical heating. We identify three eras: a Pre-Disc Era (typically \u2273 8 Gyr ago), when stars formed on dispersion-dominated orbits; an Early-Disc Era (≈8–4 Gyr ago), when stars started to form on rotation-dominated orbits but with high velocity dispersion, σform; and a Late-Disc Era (\u2272 4 Gyr ago), when stars formed with low σform. σform increased with time during the Pre-Disc Era, peaking ≈8 Gyr ago, then decreased throughout the Early-Disc Era as the disc settled and remained low throughout the Late-Disc Era. By contrast, the dispersion measured today, σnow, increases monotonically with age because of stronger post-formation heating for Pre-Disc stars. Importantly, most of σnow was in place at formation, not added post-formation, for stars younger than ≈10 Gyr. We compare the evolution of the three velocity components: at all times, σR, form > σ\u03d5, form > σZ, form. Post-formation heating primarily increased σR at ages \u2272 4 Gyr but acted nearly isotropically for older stars. The kinematics of young stars in FIRE-2 broadly agree with the range observed across the MW, M31, M33, and PHANGS-MUSE galaxies. The lookback time that the disc began to settle correlates with its dynamical state today: earlier-settling galaxies currently form colder discs. Including stellar cosmic-ray feedback does not significantly change disc rotational support at fixed stellar mass.
",
"doi": "10.1093/mnras/stad3547",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2024-01",
"series_number": "3",
"volume": "527",
"issue": "3",
"pages": "6926-6949"
},
{
"id": "authors:6fye5-hdw64",
"collection": "authors",
"collection_id": "6fye5-hdw64",
"cite_using_url": "https://authors.library.caltech.edu/records/6fye5-hdw64",
"type": "article",
"title": "Scaling K2. VII. Evidence For a High Occurrence Rate of Hot Sub-Neptunes at Intermediate Ages",
"author": [
{
"family_name": "Christiansen",
"given_name": "Jessie L.",
"orcid": "0000-0002-8035-4778",
"clpid": "Christiansen-Jessie-L"
},
{
"family_name": "Zink",
"given_name": "Jon K.",
"orcid": "0000-0003-1848-2063",
"clpid": "Zink-Jon-K"
},
{
"family_name": "Hardegree-Ullman",
"given_name": "Kevin K.",
"orcid": "0000-0003-3702-0382",
"clpid": "Hardegree-Ullman-Kevin-K"
},
{
"family_name": "Fernandes",
"given_name": "Rachel B.",
"orcid": "0000-0002-3853-7327",
"clpid": "Fernandes-Rachel-B"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Rebull",
"given_name": "Luisa M.",
"orcid": "0000-0001-6381-515X",
"clpid": "Rebull-Luisa-M"
},
{
"family_name": "Boley",
"given_name": "Kiersten M.",
"orcid": "0000-0001-8153-639X",
"clpid": "Boley-Kiersten-M"
},
{
"family_name": "Bergsten",
"given_name": "Galen J.",
"orcid": "0000-0003-4500-8850",
"clpid": "Bergsten-Galen-J"
},
{
"family_name": "Bhure",
"given_name": "Sakhee",
"orcid": "0000-0002-6673-8206",
"clpid": "Bhure-Sakhee"
}
],
"abstract": "The NASA K2 mission obtained high-precision time-series photometry for four young clusters, including the near-twin 600\u2013800 Myr old Praesepe and Hyades clusters. Hot sub-Neptunes are highly prone to mass-loss mechanisms, given their proximity to the host star and the weakly bound gaseous envelopes, and analyzing this population at young ages can provide strong constraints on planetary evolution models. Using our automated transit detection pipeline, we recover 15 planet candidates across the two clusters, including 10 previously confirmed planets. We find a hot sub-Neptune occurrence rate of 79%\u2013107% for GKM stars in the Praesepe cluster. This is 2.5\u20133.5\u03c3 higher than the occurrence rate of 16.54_(\u2212 0.98)^(+1.00) % for the same planets orbiting the \u223c3\u20139 Gyr old GKM field stars observed by K2, even after accounting for the slightly supersolar metallicity ([Fe/H] \u223c 0.2 dex) of the Praesepe cluster. We examine the effect of adding \u223c100 targets from the Hyades cluster and extending the planet parameter space under examination, and we find similarly high occurrence rates in both cases. The high occurrence rate of young, hot sub-Neptunes could indicate either that these planets are undergoing atmospheric evolution as they age, or that planetary systems that formed when the Galaxy was much younger are substantially different than from today. Under the assumption of the atmospheric mass-loss scenario, a significantly higher occurrence rate of these planets at the intermediate ages of Praesepe and Hyades appears more consistent with the core-powered mass-loss scenario for the origin of the planet radius valley, compared to the photoevaporation scenario.
",
"doi": "10.3847/1538-3881/acf9f9",
"issn": "0004-6256",
"publisher": "American Astronomical Society",
"publication": "The Astronomical Journal",
"publication_date": "2023-12",
"series_number": "6",
"volume": "166",
"issue": "6",
"pages": "248"
},
{
"id": "authors:ffxqs-dps96",
"collection": "authors",
"collection_id": "ffxqs-dps96",
"cite_using_url": "https://authors.library.caltech.edu/records/ffxqs-dps96",
"type": "article",
"title": "Orientations of Dark Matter Halos in FIRE-2 Milky Way\u2013mass Galaxies",
"author": [
{
"family_name": "Baptista",
"given_name": "Jay",
"orcid": "0000-0002-9306-1704"
},
{
"family_name": "Sanderson",
"given_name": "Robyn",
"orcid": "0000-0003-3939-3297"
},
{
"family_name": "Huber",
"given_name": "Dan",
"orcid": "0000-0001-8832-4488"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942"
},
{
"family_name": "Sameie",
"given_name": "Omid",
"orcid": "0000-0003-4394-6085"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X"
},
{
"family_name": "Bailin",
"given_name": "Jeremy",
"orcid": "0000-0001-6380-010X"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Giguere",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628"
},
{
"family_name": "Chakrabarti",
"given_name": "Sukanya",
"orcid": "0000-0001-6711-8140"
},
{
"family_name": "Vargya",
"given_name": "Drona"
},
{
"family_name": "Panithanpaisal",
"given_name": "Nondh",
"orcid": "0000-0001-5214-8822"
},
{
"family_name": "Arora",
"given_name": "Arpit",
"orcid": "0000-0002-8354-7356"
},
{
"family_name": "Cunningham",
"given_name": "Emily",
"orcid": "0000-0002-6993-0826"
}
],
"abstract": "The shape and orientation of dark matter (DM) halos are sensitive to the microphysics of the DM particles, yet in many mass models, the symmetry axes of the Milky Way's DM halo are often assumed to be aligned with the symmetry axes of the stellar disk. This is well motivated for the inner DM halo, but not for the outer halo. We use zoomed-in cosmological baryonic simulations from the Latte suite of FIRE-2 Milky Way–mass galaxies to explore the evolution of the DM halo's orientation with radius and time, with or without a major merger with a Large Magellanic Cloud analog, and when varying the DM model. In three of the four cold DM halos we examine, the orientation of the halo minor axis diverges from the stellar disk vector by more than 20° beyond about 30 galactocentric kpc, reaching a maximum of 30°–90°, depending on the individual halo's formation history. In identical simulations using a model of self-interacting DM with σ = 1 cm2 g−1, the halo remains aligned with the stellar disk out to ∼200–400 kpc. Interactions with massive satellites (M \u2273 4 × 1010M\u2299 at pericenter; M \u2273 3.3 × 1010M\u2299 at infall) affect the orientation of the halo significantly, aligning the halo's major axis with the satellite galaxy from the disk to the virial radius. The relative orientation of the halo and disk beyond 30 kpc is a potential diagnostic of self-interacting DM, if the effects of massive satellites can be accounted for.
",
"doi": "10.3847/1538-4357/acea79",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2023-11-20",
"series_number": "1",
"volume": "958",
"issue": "1",
"pages": "44"
},
{
"id": "authors:mkvs8-vmb66",
"collection": "authors",
"collection_id": "mkvs8-vmb66",
"cite_using_url": "https://authors.library.caltech.edu/records/mkvs8-vmb66",
"type": "article",
"title": "Predicting the Radiation Field of Molecular Clouds Using Denoising Diffusion Probabilistic Models",
"author": [
{
"family_name": "Xu",
"given_name": "Duo",
"orcid": "0000-0001-6216-8931"
},
{
"family_name": "Offner",
"given_name": "Stella S. R.",
"orcid": "0000-0003-1252-9916"
},
{
"family_name": "Gutermuth",
"given_name": "Robert",
"orcid": "0000-0002-6447-899X"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604"
},
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Accurately quantifying the impact of radiation feedback in star formation is challenging. To address this complex problem, we employ deep-learning techniques known as denoising diffusion probabilistic models (DDPMs) to predict the interstellar radiation field (ISRF) strength based on three-band dust emission at 4.5, 24, and 250 μm. We adopt magnetohydrodynamic simulations from the STARFORGE project that model star formation and giant molecular cloud (GMC) evolution. We generate synthetic dust emission maps matching observed spectral energy distributions in the Monoceros R2 (MonR2) GMC. We train DDPMs to estimate the ISRF using synthetic three-band dust emission. The dispersion between the predictions and true values is within a factor of 0.1 for the test set. We extended our assessment of the diffusion model to include new simulations with varying physical parameters. While there is a consistent offset observed in these out-of-distribution simulations, the model effectively constrains the relative intensity to within a factor of 2. Meanwhile, our analysis reveals a weak correlation between the ISRF solely derived from dust temperature and the actual ISRF. We apply our trained model to predict the ISRF in MonR2, revealing a correspondence between intense ISRF, bright sources, and high dust emission, confirming the model's ability to capture ISRF variations. Our model robustly predicts radiation feedback distribution, even in complex, poorly constrained ISRF environments like those influenced by nearby star clusters. However, precise ISRF predictions require an accurate training data set mirroring the target molecular cloud's unique physical conditions.
",
"doi": "10.3847/1538-4357/acfedc",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2023-11-20",
"series_number": "1",
"volume": "958",
"issue": "1",
"pages": "97"
},
{
"id": "authors:4853b-ctm67",
"collection": "authors",
"collection_id": "4853b-ctm67",
"cite_using_url": "https://authors.library.caltech.edu/records/4853b-ctm67",
"type": "article",
"title": "Novel conservative methods for adaptive force softening in collisionless and multispecies N-body simulations",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Nadler",
"given_name": "Ethan O",
"orcid": "0000-0002-1182-3825"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y",
"orcid": "0000-0002-1655-5604"
},
{
"family_name": "Shen",
"given_name": "Xuejian",
"orcid": "0000-0002-6196-823X",
"clpid": "Shen-Xuejian"
},
{
"family_name": "Sands",
"given_name": "Isabel",
"orcid": "0000-0002-1159-4882",
"clpid": "Sands-Isabel"
},
{
"family_name": "Jiang",
"given_name": "Fangzhou",
"orcid": "0000-0001-6115-0633",
"clpid": "Jiang-Fangzhou"
}
],
"abstract": "Modelling self-gravity of collisionless fluids (e.g. ensembles of dark matter, stars, black holes, dust, and planetary bodies) in simulations is challenging and requires some force softening. It is often desirable to allow softenings to evolve adaptively, in any high-dynamic range simulation, but this poses unique challenges of consistency, conservation, and accuracy, especially in multiphysics simulations where species with different 'softening laws' may interact. We therefore derive a generalized form of the energy-and-momentum conserving gravitational equations of motion, applicable to arbitrary rules used to determine the force softening, together with consistent associated time-step criteria, interaction terms between species with different softening laws, and arbitrary maximum/minimum softenings. We also derive new methods to maintain better accuracy and conservation when symmetrizing forces between particles. We review and extend previously discussed adaptive softening schemes based on the local neighbour particle density, and present several new schemes for scaling the softening with properties of the gravitational field, i.e. the potential or acceleration or tidal tensor. We show that the 'tidal softening' scheme not only represents a physically motivated, translation and Galilean invariant and equivalence-principle respecting (and therefore conservative) method but also imposes negligible time-step or other computational penalties, ensuring that pairwise two-body scattering is small compared to smooth background forces and can resolve outstanding challenges in properly capturing tidal disruption of substructures (minimizing artificial destruction) while also avoiding excessive N-body heating. We make all of this public in the GIZMO code.
",
"doi": "10.1093/mnras/stad2548",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2023-11",
"series_number": "4",
"volume": "525",
"issue": "4",
"pages": "5951-5977"
},
{
"id": "authors:rymc5-8jp48",
"collection": "authors",
"collection_id": "rymc5-8jp48",
"cite_using_url": "https://authors.library.caltech.edu/records/rymc5-8jp48",
"type": "article",
"title": "Dust dynamics in AGN winds: a new mechanism for multiwavelength AGN variability",
"author": [
{
"family_name": "Soliman",
"given_name": "Nadine H",
"orcid": "0000-0002-6810-1110",
"clpid": "Soliman-Nadine-H"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Partial dust obscuration in active galactic nuclei (AGNs) has been proposed as a potential explanation for some cases of AGN variability. The dust–gas mixture present in AGN tori is accelerated by radiation pressure, leading to the launching of an AGN wind. Dust under these conditions has been shown to be unstable to a generic class of fast-growing resonant drag instabilities (RDIs). In this work, we present the first numerical simulations of radiation-driven outflows that explicitly include dust dynamics in conditions resembling AGN winds. We investigate the implications of RDIs on the torus morphology, AGN variability, and the ability of radiation to effectively launch a wind. We find that the RDIs rapidly develop, reaching saturation at times much shorter than the global time-scales of the outflows, resulting in the formation of filamentary structure on box-size scales with strong dust clumping and super-Alfvénic velocity dispersions. The instabilities lead to fluctuations in dust opacity and gas column density of 10–20 per cent when integrated along mock observed lines of sight to the quasar accretion disc. These fluctuations occur over year to decade time-scales and exhibit a red-noise power spectrum commonly observed for AGNs. Additionally, we find that the radiation effectively couples with the dust–gas mixture, launching highly supersonic winds that entrain 70–90 per cent of the gas, with a factor of \u22723 photon momentum loss relative to the predicted multiple-scattering momentum loading rate. Therefore, our findings suggest that RDIs play an important role in driving the clumpy nature of AGN tori and generating AGN variability consistent with observations.
",
"doi": "10.1093/mnras/stad2460",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2023-10",
"series_number": "2",
"volume": "525",
"issue": "2",
"pages": "2668-2689"
},
{
"id": "authors:jm4tn-b3727",
"collection": "authors",
"collection_id": "jm4tn-b3727",
"cite_using_url": "https://authors.library.caltech.edu/records/jm4tn-b3727",
"type": "article",
"title": "What causes the formation of discs and end of bursty star formation?",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Gurvich",
"given_name": "Alexander B.",
"orcid": "0000-0002-6145-3674",
"clpid": "Gurvich-Alexander-B"
},
{
"family_name": "Shen",
"given_name": "Xuejian",
"orcid": "0000-0002-6196-823X",
"clpid": "Shen-Xuejian"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-Michael-Y"
},
{
"family_name": "Kurinchi-Vendhan",
"given_name": "Shalini",
"clpid": "Kurinchi-Vendhan-Shalini"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Jiang",
"given_name": "Fangzhou",
"orcid": "0000-0001-6115-0633",
"clpid": "Jiang-Fangzhou"
},
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-Matthew-E"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565",
"clpid": "Stern-Jonathan"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Bullock",
"given_name": "James",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-Coral-R"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Loebman",
"given_name": "Sarah R.",
"orcid": "0000-0003-3217-5967",
"clpid": "Loebman-Sarah-R"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232",
"clpid": "Moreno-Jorge"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
}
],
"abstract": "As they grow, galaxies can transition from irregular/spheroidal with ‘bursty’ star formation histories (SFHs), to discy with smooth SFHs. But even in simulations, the direct physical cause of such transitions remains unclear. We therefore explore this in a large suite of numerical experiments re-running portions of cosmological simulations with widely varied physics, further validated with existing FIRE simulations. We show that gas supply, cooling/thermodynamics, star formation model, Toomre scale, galaxy dynamical times, and feedback properties do not have a direct causal effect on these transitions. Rather, both the formation of discs and cessation of bursty star formation are driven by the gravitational potential, but in different ways. Disc formation is promoted when the mass profile becomes sufficiently centrally concentrated in shape (relative to circularization radii): we show that this provides a well-defined dynamical centre, ceases to support the global ‘breathing modes’ that can persist indefinitely in less-concentrated profiles and efficiently destroy discs, promotes orbit mixing to form a coherent angular momentum, and stabilizes the disc. Smooth SF is promoted by the potential or escape velocity Vesc (not circular velocity Vc) becoming sufficiently large at the radii of star formation that cool, mass-loaded (momentum-conserving) outflows are trapped/confined near the galaxy, as opposed to escaping after bursts. We discuss the detailed physics, how these conditions arise in cosmological contexts, their relation to other correlated phenomena (e.g. inner halo virialization, vertical disc ‘settling’), and observations.
",
"doi": "10.1093/mnras/stad1902",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2023-10",
"series_number": "2",
"volume": "525",
"issue": "2",
"pages": "2241-2286"
},
{
"id": "authors:8c6bm-5xf42",
"collection": "authors",
"collection_id": "8c6bm-5xf42",
"cite_using_url": "https://authors.library.caltech.edu/records/8c6bm-5xf42",
"type": "article",
"title": "Simulating Atomic Dark Matter in Milky Way Analogs",
"author": [
{
"family_name": "Roy",
"given_name": "Sandip",
"orcid": "0000-0002-7638-7454"
},
{
"family_name": "Shen",
"given_name": "Xuejian",
"orcid": "0000-0002-6196-823X",
"clpid": "Shen-Xuejian"
},
{
"family_name": "Lisanti",
"given_name": "Mariangela",
"orcid": "0000-0002-8495-8659"
},
{
"family_name": "Curtin",
"given_name": "David",
"orcid": "0000-0003-0263-6195"
},
{
"family_name": "Murray",
"given_name": "Norman",
"orcid": "0000-0002-8659-3729"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Dark sector theories naturally lead to multicomponent scenarios for dark matter where a subcomponent can dissipate energy through self-interactions, allowing it to efficiently cool inside galaxies. We present the first cosmological hydrodynamical simulations of Milky Way analogs where the majority of dark matter is collisionless cold dark matter (CDM) but a subcomponent (6%) is strongly dissipative minimal atomic dark matter (ADM). The simulations, implemented in GIZMO and utilizing FIRE-2 galaxy formation physics to model the standard baryonic sector, demonstrate that the addition of even a small fraction of dissipative dark matter can significantly impact galactic evolution despite being consistent with current cosmological constraints. We show that ADM gas with roughly standard model–like masses and couplings can cool to form a rotating \"dark disk\" with angular momentum closely aligned with the visible stellar disk. The morphology of the disk depends sensitively on the parameters of the ADM model, which affect the cooling rates in the dark sector. The majority of the ADM gas gravitationally collapses into dark \"clumps\" (regions of black hole or mirror star formation), which form a prominent bulge and a rotating thick disk in the central galaxy. These clumps form early and quickly sink to the inner ∼kiloparsec of the galaxy, affecting the galaxy's star formation history and present-day baryonic and CDM distributions.
",
"doi": "10.3847/2041-8213/ace2c8",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2023-09-10",
"series_number": "2",
"volume": "954",
"issue": "2",
"pages": "L40"
},
{
"id": "authors:t6cc8-a8j51",
"collection": "authors",
"collection_id": "t6cc8-a8j51",
"cite_using_url": "https://authors.library.caltech.edu/records/t6cc8-a8j51",
"type": "article",
"title": "Local positive feedback in the overall negative: the impact of quasar winds on star formation in the FIRE cosmological simulations",
"author": [
{
"family_name": "Mercedes-Feliz",
"given_name": "Jonathan",
"orcid": "0000-0002-8390-6726"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945"
},
{
"family_name": "Hayward",
"given_name": "Christopher C",
"orcid": "0000-0003-4073-3236"
},
{
"family_name": "Cochrane",
"given_name": "Rachel K",
"orcid": "0000-0001-8855-6107"
},
{
"family_name": "Terrazas",
"given_name": "Bryan A",
"orcid": "0000-0001-5529-7305"
},
{
"family_name": "Wellons",
"given_name": "Sarah",
"orcid": "0000-0002-3977-2724"
},
{
"family_name": "Richings",
"given_name": "Alexander J",
"orcid": "0000-0003-0502-9235"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232"
},
{
"family_name": "Su",
"given_name": "Kung Yi",
"orcid": "0000-0003-1598-0083"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067"
}
],
"abstract": "Negative feedback from accreting supermassive black holes is considered crucial in suppressing star formation and quenching massive galaxies. However, several models and observations suggest that black hole feedback may have a positive effect, triggering star formation by compressing interstellar medium gas to higher densities. We investigate the dual role of black hole feedback using cosmological hydrodynamic simulations from the Feedback In Realistic Environment (FIRE) project, incorporating a novel implementation of hyper-refined accretion-disc winds. Focusing on a massive, star-forming galaxy at z ∼ 2 (M_(halo) ~ 10^(12.5) M\u2299), we demonstrate that strong quasar winds with a kinetic power of ∼10\u2074\u2076 erg s\u207b¹, persisting for over 20 Myr, drive the formation of a central gas cavity and significantly reduce the surface density of star formation across the galaxy's disc. The suppression of star formation primarily occurs by limiting the availability of gas for star formation rather than by evacuating the pre-existing star-forming gas reservoir (preventive feedback dominates over ejective feedback). Despite the overall negative impact of quasar winds, we identify several potential indicators of local positive feedback, including (1) the spatial anticorrelation between wind-dominated regions and star-forming clumps, (2) higher local star formation efficiency in compressed gas at the edge of the cavity, and (3) increased contribution of outflowing material to local star formation. Moreover, stars formed under the influence of quasar winds tend to be located at larger radial distances. Our findings suggest that both positive and negative AGN feedback can coexist within galaxies, although the local positive triggering of star formation has a minor influence on global galaxy growth.
",
"doi": "10.1093/mnras/stad2079",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2023-09",
"series_number": "3",
"volume": "524",
"issue": "3",
"pages": "3446-3463"
},
{
"id": "authors:dj8a7-vfc28",
"collection": "authors",
"collection_id": "dj8a7-vfc28",
"cite_using_url": "https://authors.library.caltech.edu/records/dj8a7-vfc28",
"type": "article",
"title": "Born this way: thin disc, thick disc, and isotropic spheroid formation in FIRE-2 Milky Way\u2013mass galaxy simulations",
"author": [
{
"family_name": "Yu",
"given_name": "Sijie",
"orcid": "0000-0002-1019-0341"
},
{
"family_name": "Bullock",
"given_name": "James S",
"orcid": "0000-0003-4298-5082"
},
{
"family_name": "Gurvich",
"given_name": "Alexander B",
"orcid": "0000-0002-6145-3674"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232"
}
],
"abstract": "We investigate the formation of Milky Way–mass galaxies using FIRE-2 ΛCDM cosmological zoom-in simulations by studying the orbital evolution of stars formed in the main progenitor of the galaxy, from birth to the present day. We classify in situ stars as isotropic spheroid, thick-disc, and thin-disc according to their orbital circularities and show that these components are assembled in a time-ordered sequence from early to late times, respectively. All simulated galaxies experience an early phase of bursty star formation that transitions to a late-time steady phase. This transition coincides with the time that the inner CGM virializes. During the early bursty phase, galaxies have irregular morphologies and new stars are born on radial orbits; these stars evolve into an isotropic spheroidal population today. The bulk of thick-disc stars form at intermediate times, during a clumpy-disc 'spin-up' phase, slightly later than the peak of spheroid formation. At late times, once the CGM virializes and star formation 'cools down,' stars are born on circular orbits within a narrow plane. Those stars mostly inhabit thin discs today. Broadly speaking, stars with disc-like or spheroid-like orbits today were born that way. Mergers on to discs and secular processes do affect kinematics in our simulations, but play only secondary roles in populating thick-disc and in situ spheroid populations at z = 0. The age distributions of spheroid, thick disc, and thin disc populations scale self-similarly with the steady-phase transition time, which suggests that morphological age dating can be linked to the CGM virialization time in galaxies.
",
"doi": "10.1093/mnras/stad1806",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2023-08",
"series_number": "4",
"volume": "523",
"issue": "4",
"pages": "6220-6238"
},
{
"id": "authors:4t4c5-75776",
"collection": "authors",
"collection_id": "4t4c5-75776",
"cite_using_url": "https://authors.library.caltech.edu/records/4t4c5-75776",
"type": "article",
"title": "The impact of AGN-driven winds on physical and observable galaxy sizes",
"author": [
{
"family_name": "Cochrane",
"given_name": "R. K.",
"orcid": "0000-0001-8855-6107",
"clpid": "Cochrane-Rachel-K"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "D.",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Mercedes-Feliz",
"given_name": "J.",
"orcid": "0000-0002-8390-6726",
"clpid": "Mercedes-Feliz-Jonathan"
},
{
"family_name": "Hayward",
"given_name": "C. C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "C.-A.",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Wellons",
"given_name": "S.",
"orcid": "0000-0002-3977-2724",
"clpid": "Wellons-Sarah"
},
{
"family_name": "Terrazas",
"given_name": "B. A.",
"orcid": "0000-0001-5529-7305",
"clpid": "Terrazas-Bryan-A"
},
{
"family_name": "Wetzel",
"given_name": "A.",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Hopkins",
"given_name": "P. F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Moreno",
"given_name": "J",
"orcid": "0000-0002-3430-3232"
},
{
"family_name": "Su",
"given_name": "K.-Y.",
"orcid": "0000-0003-1598-0083",
"clpid": "Su-Kung-Yi"
},
{
"family_name": "Somerville",
"given_name": "R. S.",
"orcid": "0000-0002-6748-6821",
"clpid": "Somerville-Rachel-S"
}
],
"abstract": "Without active galactic nucleus (AGN) feedback, simulated massive, star-forming galaxies become too compact relative to observed galaxies at z \u2272 2. In this paper, we perform high-resolution re-simulations of a massive (\u2060\ud835\udc40\u22c6 ∼ 10¹¹ M_\u2299\u2060) galaxy at z ∼ 2.3, drawn from the Feedback in Realistic Environments (FIRE) project. In the simulation without AGN feedback, the galaxy experiences a rapid starburst and shrinking of its half-mass radius. We experiment with driving mechanical AGN winds, using a state-of-the-art hyper-Lagrangian refinement technique to increase particle resolution. These winds reduce the gas surface density in the inner regions of the galaxy, suppressing the compact starburst and maintaining an approximately constant half-mass radius. Using radiative transfer, we study the impact of AGN feedback on the magnitude and extent of the multiwavelength continuum emission. When AGN winds are included, the suppression of the compact, dusty starburst results in lowered flux at FIR wavelengths (due to decreased star formation) but increased flux at optical-to-near-IR wavelengths (due to decreased dust attenuation, in spite of the lowered star formation rate), relative to the case without AGN winds. The FIR half-light radius decreases from ∼1 to ∼0.1kpc in \u227240Myr when AGN winds are not included, but increases to ∼2kpc when they are. Interestingly, the half-light radius at optical-NIR wavelengths remains approximately constant over 35Myr\u2060, for simulations with and without AGN winds. In the case without winds, this occurs despite the rapid compaction, and is due to heavy dust obscuration in the inner regions of the galaxy. This work highlights the importance of forward-modelling when comparing simulated and observed galaxy populations.
",
"doi": "10.1093/mnras/stad1528",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2023-08",
"series_number": "2",
"volume": "523",
"issue": "2",
"pages": "2409-2421"
},
{
"id": "authors:1py2v-a1t89",
"collection": "authors",
"collection_id": "1py2v-a1t89",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230714-263898400.3",
"type": "article",
"title": "FIREbox: simulating galaxies at high dynamic range in a cosmological volume",
"author": [
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "\u00c7atmabacak",
"given_name": "Onur",
"orcid": "0000-0003-4067-1434",
"clpid": "\u00c7atmabacak-Onur"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Bassini",
"given_name": "Luigi",
"orcid": "0000-0002-6864-7762",
"clpid": "Bassini-Luigi"
},
{
"family_name": "Bernardini",
"given_name": "Mauro",
"orcid": "0000-0002-2930-9509",
"clpid": "Bernardini-Mauro"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Cenci",
"given_name": "Elia",
"orcid": "0000-0002-0766-1704",
"clpid": "Cenci-Elia"
},
{
"family_name": "Gensior",
"given_name": "Jindra",
"orcid": "0000-0001-6119-9883",
"clpid": "Gensior-Jindra"
},
{
"family_name": "Liang",
"given_name": "Lichen",
"orcid": "0000-0001-9422-0095",
"clpid": "Liang-Lichen"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232",
"clpid": "Moreno-Jorge"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
}
],
"abstract": "We introduce a suite of cosmological volume simulations to study the evolution of galaxies as part of the Feedback in Realistic Environments project. FIREbox, the principal simulation of the present suite, provides a representative sample of galaxies (\u223c1000 galaxies with M\u209b\u209c\u2090\u1d63 > 10\u2078 M_\u2299 at z = 0) at a resolution (\u0394x ~ 20 pc, m_b ~ 6 x 10\u2074 M_\u2299) comparable to state-of-the-art galaxy zoom-in simulations. FIREbox captures the multiphase nature of the interstellar medium in a fully cosmological setting (L = 22.1 Mpc) thanks to its exceptionally high dynamic range (\u227310\u2076) and the inclusion of multichannel stellar feedback. Here, we focus on validating the simulation predictions by comparing to observational data. We find that star formation rates, gas masses, and metallicities of simulated galaxies with M\u209b\u209c\u2090\u1d63 < 10^(10.5-11) M_\u2299) broadly agree with observations. These galaxy scaling relations extend to low masses (M\u209b\u209c\u2090\u1d63 ~ 10\u2077 M_\u2299) and follow a (broken) power-law relationship. Also reproduced are the evolution of the cosmic HI density and the HI column density distribution at z \u223c 0\u20135. At low z , FIREbox predicts a peak in the stellar-mass\u2013halo-mass relation but also a higher abundance of massive galaxies and a higher cosmic star formation rate density than observed, showing that stellar feedback alone is insufficient to reproduce the properties of massive galaxies at late times. Given its high resolution and sample size, FIREbox offers a baseline prediction of galaxy formation theory in a \u039bCDM Universe while also highlighting modelling challenges to be addressed in next-generation galaxy simulations.",
"doi": "10.1093/mnras/stad1205",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2023-07",
"series_number": "3",
"volume": "522",
"issue": "3",
"pages": "3831-3860"
},
{
"id": "authors:6apqh-cz454",
"collection": "authors",
"collection_id": "6apqh-cz454",
"cite_using_url": "https://authors.library.caltech.edu/records/6apqh-cz454",
"type": "article",
"title": "TRINITY II: The luminosity-dependent bias of the supermassive black hole mass\u2013galaxy mass relation for bright quasars at z \u00a0=\u00a06",
"author": [
{
"family_name": "Zhang",
"given_name": "Haowen",
"orcid": "0000-0002-4321-3538"
},
{
"family_name": "Behroozi",
"given_name": "Peter",
"orcid": "0000-0002-2517-6446"
},
{
"family_name": "Volonteri",
"given_name": "Marta",
"orcid": "0000-0002-3216-1322"
},
{
"family_name": "Silk",
"given_name": "Joseph",
"orcid": "0000-0002-1566-8148"
},
{
"family_name": "Fan",
"given_name": "Xiaohui",
"orcid": "0000-0003-3310-0131"
},
{
"family_name": "Aird",
"given_name": "James",
"orcid": "0000-0003-1908-8463"
},
{
"family_name": "Yang",
"given_name": "Jinyi",
"orcid": "0000-0001-5287-4242"
},
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Using recent empirical constraints on the dark matter halo–galaxy–supermassive black hole (SMBH) connection from z = 0–7, we infer how undermassive, typical, and overmassive SMBHs contribute to the quasar luminosity function (QLF) at z = 6. We find that beyond Lbol = 5 × 1046 erg s−1, the z = 6 QLF is dominated by SMBHs that are at least 0.3 dex above the z = 6 median M•–M* relation. The QLF is dominated by typical SMBHs (i.e. within ±0.3 dex around the M•–M* relation) at Lbol \u2272 1045 erg s−1. At z ∼ 6, the intrinsic M•–M* relation for all SMBHs is slightly steeper than the z = 0 scaling, with a similar normalization at M* ~ 1011\u2299. We also predict the M•–M* relation for z = 6 bright quasars selected by different bolometric luminosity thresholds, finding very good agreement with observations. For quasars with Lbol > 3 × 1046 (1048) erg s−1, the scaling relation is shifted upwards by ∼0.35 (1.0) dex for 1011M\u2299 galaxies. To accurately measure the intrinsic M•–M* relation, it is essential to include fainter quasars with Lbol \u2272 1045 erg s−1. At high redshifts, low-luminosity quasars are thus the best targets for understanding typical formation paths for SMBHs in galaxies.
",
"doi": "10.1093/mnrasl/slad060",
"issn": "1745-3925",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society: Letters",
"publication_date": "2023-07",
"series_number": "1",
"volume": "523",
"issue": "1",
"pages": "L69-L74"
},
{
"id": "authors:6qmc2-rh077",
"collection": "authors",
"collection_id": "6qmc2-rh077",
"cite_using_url": "https://authors.library.caltech.edu/records/6qmc2-rh077",
"type": "article",
"title": "Formation of proto-globular cluster candidates in cosmological simulations of dwarf galaxies at z > 4",
"author": [
{
"family_name": "Sameie",
"given_name": "Omid",
"orcid": "0000-0003-4394-6085",
"clpid": "Sameie-Omid"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Samuel",
"given_name": "Jenna",
"orcid": "0000-0002-8429-4100",
"clpid": "Samuel-Jenna"
},
{
"family_name": "Schauer",
"given_name": "Anna T. P.",
"orcid": "0000-0002-2220-8086",
"clpid": "Schauer-Anna-T-P"
},
{
"family_name": "Weisz",
"given_name": "Daniel R.",
"orcid": "0000-0002-6442-6030",
"clpid": "Weisz-Daniel-R"
}
],
"abstract": "We perform cosmological hydrodynamical simulations to study the formation of proto-globular cluster candidates in progenitors of present-day dwarf galaxies (M\u1d65\u1d62\u1d63 ≈ 10¹\u2070 M\u2299 at z = 0) as part of the ‘Feedback in Realistic Environment’ (FIRE) project. Compact (r1/2 < 30 pc), relatively massive (0.5 × 105 \u2272 M\u22c6/M\u2299 \u2272 5 × 105), self-bound stellar clusters form at 11 \u2273 z \u2273 5 in progenitors with \u2060M\u1d65\u1d62\u1d63 ≈ 10\u2079 M\u2299. Cluster formation is triggered when at least 10\u2077 M\u2299 of dense, turbulent gas reaches Σ\u2089\u2090\u209b ≈ 10\u2074 M\u2299 pc\u207b² as a result of the compressive effects of supernova feedback or from cloud–cloud collisions. The clusters can survive for \u20602-3 Gyr; absent numerical effects, they could possibly survive substantially longer, perhaps to z = 0. The longest lived clusters are those that form at significant distance – several hundreds of pc – from their host galaxy. We therefore predict that globular clusters forming in progenitors of present-day dwarf galaxies will be offset from any pre-existing stars within their host dark matter haloes as opposed to deeply embedded within a well-defined galaxy. Properties of the nascent clusters are consistent with observations of some of the faintest and most compact high-redshift sources in Hubble Space Telescope lensing fields and are at the edge of what will be detectable as point sources in deep imaging of non-lensed fields with JWST. By contrast, the star clusters’ host galaxies will remain undetectable.
",
"doi": "10.1093/mnras/stad1071",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2023-06",
"series_number": "2",
"volume": "522",
"issue": "2",
"pages": "1800-1813"
},
{
"id": "authors:gjwtw-02n92",
"collection": "authors",
"collection_id": "gjwtw-02n92",
"cite_using_url": "https://authors.library.caltech.edu/records/gjwtw-02n92",
"type": "article",
"title": "A simple sub-grid model for cosmic ray effects on galactic scales",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Butsky",
"given_name": "Iryna S",
"orcid": "0000-0003-1257-5007",
"clpid": "Butsky-Iryna-S"
},
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067"
}
],
"abstract": "Many recent numerical studies have argued that cosmic rays (CRs) from supernovae (SNe) or active galactic nuclei (AGNs) could play a crucial role in galaxy formation, in particular by establishing a CR-pressure-dominated circumgalactic medium (CGM). But explicit CR-magnetohydrodynamics (CR-MHD) remains computationally expensive, and it is not clear whether those results can be applied to simulations that do not explicitly treat magnetic fields or resolved interstellar medium phase structure. We therefore present an intentionally extremely simplified 'sub-grid' model for CRs, which attempts to capture the key qualitative behaviors of greatest interest for those interested in simulations or semi-analytical models including some approximate CR effects on galactic (\u2273 kpc) scales, while imposing negligible computational overhead. The model is numerically akin to some recently developed sub-grid models for radiative feedback, and allows for a simple constant parametrization of the CR diffusivity and/or streaming speed; it allows for an arbitrary distribution of sources (proportional to black hole accretion rates or star–particle SNe rates or gas/galaxy star formation rates), and interpolates between the limits where CRs escape the galaxies with negligible losses and those where CRs lose most of their energy catastrophically before escape (relevant in e.g. starburst galaxies). The numerical equations are solved trivially alongside gravity in most codes. We compare this to explicit CR-MHD simulations and discuss where the (many) sub-grid approximations break down, and what drives the major sources of uncertainty.
",
"doi": "10.1093/mnras/stad976",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2023-06",
"series_number": "2",
"volume": "522",
"issue": "2",
"pages": "2936-2950"
},
{
"id": "authors:er926-jhs14",
"collection": "authors",
"collection_id": "er926-jhs14",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230502-727238500.5",
"type": "article",
"title": "A semi-analytic study of self-interacting dark-matter haloes with baryons",
"author": [
{
"family_name": "Jiang",
"given_name": "Fangzhou",
"orcid": "0000-0001-6115-0633",
"clpid": "Jiang-Fangzhou"
},
{
"family_name": "Benson",
"given_name": "Andrew",
"orcid": "0000-0001-5501-6008",
"clpid": "Benson-Andrew-J"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Slone",
"given_name": "Oren",
"orcid": "0000-0002-5999-106X",
"clpid": "Slone-Oren"
},
{
"family_name": "Lisanti",
"given_name": "Mariangela",
"orcid": "0000-0002-8495-8659",
"clpid": "Lisanti-Mariangela"
},
{
"family_name": "Kaplinghat",
"given_name": "Manoj",
"orcid": "0000-0001-8555-0164",
"clpid": "Kaplinghat-Manoj"
},
{
"family_name": "Peter",
"given_name": "Annika H. G.",
"orcid": "0000-0002-8040-6785",
"clpid": "Peter-Annika-H-G"
},
{
"family_name": "Zeng",
"given_name": "Zhichao Carton",
"orcid": "0000-0002-6008-5144",
"clpid": "Zeng-Zhichao-Carton"
},
{
"family_name": "Du",
"given_name": "Xiaolong",
"orcid": "0000-0003-0728-2533",
"clpid": "Du-Xiaolong"
},
{
"family_name": "Yang",
"given_name": "Shengqi",
"orcid": "0000-0002-0782-9116",
"clpid": "Yang-Shengqi"
},
{
"family_name": "Shen",
"given_name": "Xuejian",
"orcid": "0000-0002-6196-823X",
"clpid": "Shen-Xuejian"
}
],
"abstract": "We combine the isothermal Jeans model and the model of adiabatic halo contraction into a semi-analytic procedure for computing the density profile of self-interacting dark-matter (SIDM) haloes with the gravitational influence from the inhabitant galaxies. The model agrees well with cosmological SIDM simulations over the entire core-forming stage up to the onset of gravothermal core-collapse. Using this model, we show that the halo response to baryons is more diverse in SIDM than in CDM and depends sensitively on galaxy size, a desirable feature in the context of the structural diversity of bright dwarfs. The fast speed of the method facilitates analyses that would be challenging for numerical simulations \u2013 notably, we quantify the SIDM halo response as functions of the baryonic properties, on a fine mesh grid spanned by the baryon-to-total-mass ratio, M_b/M_(vir), and galaxy compactness, r1/2/Rvir; we show with high statistical precision that for typical Milky-Way-like systems, the SIDM profiles are similar to their CDM counterparts; and we delineate the regime of core-collapse in the Mb/Mvir \u2212 r1/2/Rvir space, for a given cross section\u00a0and concentration. Finally, we compare the isothermal Jeans model with the more sophisticated gravothermal fluid model, and show that the former yields faster core formation and agrees better with cosmological simulations. We attribute the difference to whether the target CDM halo is used as a boundary condition or as the initial condition for the gravothermal evolution, and thus comment on possible improvements of the fluid model. We have made our model publicly available at https://github.com/JiangFangzhou/SIDM.",
"doi": "10.1093/mnras/stad705",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2023-05",
"series_number": "3",
"volume": "521",
"issue": "3",
"pages": "4630-4644"
},
{
"id": "authors:1qb0h-8r961",
"collection": "authors",
"collection_id": "1qb0h-8r961",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230502-750579300.3",
"type": "article",
"title": "Constraining cosmic ray transport with observations of the circumgalactic medium",
"author": [
{
"family_name": "Butsky",
"given_name": "Iryna S.",
"orcid": "0000-0003-1257-5007",
"clpid": "Butsky-Iryna-S"
},
{
"family_name": "Nakum",
"given_name": "Shreya",
"orcid": "0000-0002-3970-3921",
"clpid": "Nakum-Shreya-Vimal"
},
{
"family_name": "Ponnada",
"given_name": "Sam B.",
"orcid": "0000-0002-7484-2695",
"clpid": "Ponnada-Sam-B"
},
{
"family_name": "Hummels",
"given_name": "Cameron B.",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron-B"
},
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Recent theoretical studies predict that the circumgalactic medium (CGM) around low-redshift, \u223cL* galaxies could have substantial non-thermal pressure support in the form of cosmic rays. However, these predictions are sensitive to the specific model of cosmic ray transport employed, which is theoretically and observationally underconstrained. In this work, we propose a novel observational constraint for calculating the lower limit of the radially averaged, effective cosmic ray transport rate, \u03ba_(eff)^(min). Under a wide range of assumptions (so long as cosmic rays do not lose a significant fraction of their energy in the galactic disc, regardless of whether the cosmic ray pressure is important or not in the CGM), we demonstrate a well-defined relationship between \u03ba_(eff)^(min) and three observable galaxy properties: the total hydrogen column density, the average star formation rate, and the gas circular velocity. We use a suite of Feedback in Realistic Environments 2 galaxy simulations with a variety of cosmic ray transport physics to demonstrate that our analytical model of \u03ba_(eff)^(min) is a robust lower limit of the true cosmic ray transport rate. We then apply our new model to calculate \u03ba_(eff)^(min) for galaxies in the COS-Halos sample, and confirm this already reveals strong evidence for an effective transport rate that rises rapidly away from the interstellar medium to values \u03ba_(eff)^(min) \u2273 10^(30-31) cm\u00b2 s\u207b\u00b9 (corresponding to anisotropic streaming velocities of v^(stream)_(eff) \u2273 1000 km s\u207b\u00b9) in the diffuse CGM, at impact parameters larger than 50\u2013100\u2009kpc. We discuss how future observations can provide qualitatively new constraints in our understanding of cosmic rays in the CGM and intergalactic medium.",
"doi": "10.1093/mnras/stad671",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2023-05",
"series_number": "2",
"volume": "521",
"issue": "2",
"pages": "2477-2483"
},
{
"id": "authors:acfch-psa52",
"collection": "authors",
"collection_id": "acfch-psa52",
"cite_using_url": "https://authors.library.caltech.edu/records/acfch-psa52",
"type": "article",
"title": "Public Data Release of the FIRE-2 Cosmological Zoom-in Simulations of Galaxy Formation",
"author": [
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Sanderson",
"given_name": "Robyn E.",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-Robyn-E"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-Coral-R"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
},
{
"family_name": "Nikakhtar",
"given_name": "Farnik",
"orcid": "0000-0002-3641-4366",
"clpid": "Nikakhtar-Farnik"
},
{
"family_name": "Panithanpaisal",
"given_name": "Nondh",
"orcid": "0000-0001-5214-8822",
"clpid": "Panithanpaisal-Nondh"
},
{
"family_name": "Arora",
"given_name": "Arpit",
"orcid": "0000-0002-8354-7356",
"clpid": "Arora-Arpit"
},
{
"family_name": "Gurvich",
"given_name": "Alexander B.",
"orcid": "0000-0002-6145-3674",
"clpid": "Gurvich-Alexander-B"
},
{
"family_name": "Samuel",
"given_name": "Jenna",
"orcid": "0000-0002-8429-4100",
"clpid": "Samuel-Jenna"
},
{
"family_name": "Sameie",
"given_name": "Omid",
"orcid": "0000-0003-4394-6085",
"clpid": "Sameie-Omid"
},
{
"family_name": "Pandya",
"given_name": "Viraj",
"orcid": "0000-0002-2499-9205",
"clpid": "Pandya-Viraj"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Hummels",
"given_name": "Cameron",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron-B"
},
{
"family_name": "Loebman",
"given_name": "Sarah",
"orcid": "0000-0003-3217-5967",
"clpid": "Loebman-Sarah-R"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "\n
We describe a public data release of the FIRE-2 cosmological zoom-in simulations of galaxy formation (available at http://flathub.flatironinstitute.org/fire) from the Feedback In Realistic Environments (FIRE) project. FIRE-2 simulations achieve parsec-scale resolution to explicitly model the multiphase interstellar medium while implementing direct models for stellar evolution and feedback, including stellar winds, core-collapse and Type Ia supernovae, radiation pressure, photoionization, and photoelectric heating. We release complete snapshots from three suites of simulations. The first comprises 20 simulations that zoom in on 14 Milky Way (MW)–mass galaxies, five SMC/LMC-mass galaxies, and four lower-mass galaxies including one ultrafaint; we release 39 snapshots across z = 0–10. The second comprises four massive galaxies, with 19 snapshots across z = 1–10. Finally, a high-redshift suite comprises 22 simulations, with 11 snapshots across z = 5–10. Each simulation also includes dozens of resolved lower-mass (satellite) galaxies in its zoom-in region. Snapshots include all stored properties for all dark matter, gas, and star particles, including 11 elemental abundances for stars and gas, and formation times (ages) of star particles. We also release accompanying (sub)halo catalogs, which include galaxy properties and member star particles. For the simulations to z = 0, including all MW-mass galaxies, we release the formation coordinates and an “ex situ” flag for all star particles, pointers to track particles across snapshots, catalogs of stellar streams, and multipole basis expansions for the halo mass distributions. We describe publicly available python packages for reading and analyzing these simulations.
\n
Formation of supermassive black holes (BHs) remains a theoretical challenge. In many models, especially beginning from stellar relic ‘seeds,’ this requires sustained super-Eddington accretion. While studies have shown BHs can violate the Eddington limit on accretion disc scales given sufficient ‘fuelling’ from larger scales, what remains unclear is whether or not BHs can actually capture sufficient gas from their surrounding interstellar medium (ISM). We explore this in a suite of multiphysics high-resolution simulations of BH growth in magnetized, star-forming dense gas complexes including dynamical stellar feedback from radiation, stellar mass-loss, and supernovae, exploring populations of seeds with masses ∼1−10\u2074M\u2299\u2060. In this initial study, we neglect feedback from the BHs: so this sets a strong upper limit to the accretion rates seeds can sustain. We show that stellar feedback plays a key role. Complexes with gravitational pressure/surface density below ∼10³M\u2299pc\u207b² are disrupted with low star formation efficiencies so provide poor environments for BH growth. But in denser cloud complexes, early stellar feedback does not rapidly destroy the clouds but does generate strong shocks and dense clumps, allowing ∼1 per cent of randomly initialized seeds to encounter a dense clump with low relative velocity and produce runaway, hyper-Eddington accretion (growing by orders of magnitude). Remarkably, mass growth under these conditions is almost independent of initial BH mass, allowing rapid intermediate-mass black hole (IMBH) formation even for stellar-mass seeds. This defines a necessary (but perhaps not sufficient) set of criteria for runaway BH growth: we provide analytic estimates for the probability of runaway growth under different ISM conditions.
",
"doi": "10.1093/mnras/stac3245",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2023-01",
"series_number": "3",
"volume": "518",
"issue": "3",
"pages": "3606-3621"
},
{
"id": "authors:cxe4h-0v908",
"collection": "authors",
"collection_id": "cxe4h-0v908",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230214-87190900.7",
"type": "article",
"title": "Rapid disc settling and the transition from bursty to steady star formation in Milky Way-mass galaxies",
"author": [
{
"family_name": "Gurvich",
"given_name": "Alexander B.",
"orcid": "0000-0002-6145-3674",
"clpid": "Gurvich-Alexander-B"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565",
"clpid": "Stern-Jonathan"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232",
"clpid": "Moreno-Jorge"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Richings",
"given_name": "Alexander J.",
"orcid": "0000-0003-0502-9235",
"clpid": "Richings-Alexander-J"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
}
],
"abstract": "Recent observations and simulations indicate substantial evolution in the properties of galaxies with time, wherein rotationally supported and steady thin discs (like those frequently observed in the local Universe) emerge from galaxies that are clumpy, irregular, and have bursty star formation rates (SFRs). To better understand the progenitors of local disc galaxies, we carry out an analysis of three FIRE-2 simulated galaxies with a mass similar to the Milky Way at redshift z = 0. We show that all three galaxies transition from bursty to steady SFRs at a redshift between z = 0.5 and z = 0.8, and that this transition coincides with the rapid (\u22721 Gyr) emergence of a rotationally supported interstellar medium (ISM). In the late phase with steady SFR, the rotational energy comprises \u227390 per cent of the total kinetic + thermal energy in the ISM, and is roughly half the gravitational energy. By contrast, during the early bursty phase, the ISM initially has a quasi-spheroidal morphology and its energetics are dominated by quasi-isotropic in- and outflows out of virial equilibrium. The subdominance of rotational support and out-of-equilibrium conditions at early times challenge the application of standard equilibrium disc models to high-redshift progenitors of Milky Way-like galaxies. We further find that the formation of a rotationally-supported ISM coincides with the onset of a thermal pressure supported inner circumgalactic medium (CGM). Before this transition, there is no clear boundary between the ISM and the inner CGM.",
"doi": "10.1093/mnras/stac3712",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-12-30",
"series_number": "2",
"volume": "519",
"issue": "2",
"pages": "2598-2614"
},
{
"id": "authors:3s09r-bft18",
"collection": "authors",
"collection_id": "3s09r-bft18",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221128-494241100.9",
"type": "article",
"title": "Standard self-confinement and extrinsic turbulence models for cosmic ray transport are fundamentally incompatible with observations",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-Jonathan"
},
{
"family_name": "Butsky",
"given_name": "Iryna S.",
"orcid": "0000-0003-1257-5007",
"clpid": "Butsky-Iryna-S"
},
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
}
],
"abstract": "Models for cosmic ray (CR) dynamics fundamentally depend on the rate of CR scattering from magnetic fluctuations. In the ISM, for CRs with energies \u223cMeV-TeV, these fluctuations are usually attributed either to 'extrinsic turbulence' (ET) \u2013 a cascade from larger scales \u2013 or 'self-confinement' (SC) \u2013 self-generated fluctuations from CR streaming. Using simple analytic arguments and detailed 'live' numerical CR transport calculations in galaxy simulations, we show that both of these, in standard form, cannot explain even basic qualitative features of observed CR spectra. For ET, any spectrum that obeys critical balance or features realistic anisotropy, or any spectrum that accounts for finite damping below the dissipation scale, predicts qualitatively incorrect spectral shapes and scalings of B/C and other species. Even if somehow one ignored both anisotropy and damping, observationally required scattering rates disagree with ET predictions by orders of magnitude. For SC, the dependence of driving on CR energy density means that it is nearly impossible to recover observed CR spectral shapes and scalings, and again there is an orders-of-magnitude normalization problem. But more severely, SC solutions with super-Alfv\u00e9nic streaming are unstable. In live simulations, they revert to either arbitrarily rapid CR escape with zero secondary production, or to bottleneck solutions with far-too-strong CR confinement and secondary production. Resolving these fundamental issues without discarding basic plasma processes requires invoking different drivers for scattering fluctuations. These must act on a broad range of scales with a power spectrum obeying several specific (but plausible) constraints.",
"doi": "10.1093/mnras/stac2909",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-12",
"series_number": "4",
"volume": "517",
"issue": "4",
"pages": "5413-5448"
},
{
"id": "authors:cgf26-rjt93",
"collection": "authors",
"collection_id": "cgf26-rjt93",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221010-454096500.10",
"type": "article",
"title": "A reduced speed-of-light formulation of the magnetohydrodynamic-particle-in-cell method",
"author": [
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "A reduced speed-of-light (RSOL) approximation is a useful technique for magnetohydrodynamic (MHD)-particle-in-cell (PIC) simulations. With an RSOL, some 'in-code' speed-of-light c~ is set to much lower values than the true c, allowing simulations to take larger time-steps (which are restricted by the Courant condition given the large CR speeds). However, due to the absence of a well-formulated RSOL implementation from the literature, with naive substitution of the true c with a RSOL, the CR properties in MHD-PIC simulations (e.g. CR energy or momentum density, gyro radius) vary artificially with respect to each other and with respect to the converged (\u2060c~ \u2192 c\u2060) solutions, with different choices of a RSOL. Here, we derive a new formulation of the MHD-PIC equations with an RSOL and show that (1) it guarantees all steady-state properties of the CR distribution function, and background plasma/MHD quantities are independent of the RSOL c~ even for c~ \u226a c\u2060; (2) it ensures that the simulation can simultaneously represent the real physical values of CR number, mass, momentum, and energy density; (3) it retains the correct physical meaning of various terms like the electric field; and (4) it ensures the numerical time-step for CRs can always be safely increased by a factor \u223c c/c~\u2060. This new RSOL formulation should enable greater self-consistency and reduced CPU cost in simulations of CR\u2013MHD interactions.",
"doi": "10.1093/mnras/stac2523",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-11",
"series_number": "4",
"volume": "516",
"issue": "4",
"pages": "5143-5147"
},
{
"id": "authors:342v4-ctp81",
"collection": "authors",
"collection_id": "342v4-ctp81",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221003-756400000.16",
"type": "article",
"title": "First predicted cosmic ray spectra, primary-to-secondary ratios, and ionization rates from MHD galaxy formation simulations",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Butsky",
"given_name": "Iryna S.",
"orcid": "0000-0003-1257-5007",
"clpid": "Butsky-Iryna-S"
},
{
"family_name": "Panopoulou",
"given_name": "Georgia V.",
"orcid": "0000-0001-7482-5759",
"clpid": "Panopoulou-Georgia-V"
},
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
}
],
"abstract": "We present the first simulations evolving resolved spectra of cosmic rays (CRs) from MeV\u2013TeV energies (including electrons, positrons, (anti)protons, and heavier nuclei), in live kinetic-magnetohydrodynamics galaxy simulations with star formation and feedback. We utilize new numerical methods including terms often neglected in historical models, comparing Milky Way analogues with phenomenological scattering coefficients \u03bd to Solar-neighbourhood [Local interstellar medium (LISM)] observations (spectra, B/C, e\u207a/e\u207b, p\u0305/\u03c1, \u00b9\u2070Be/\u2079Be, ionization, and \u03b3-rays). We show it is possible to reproduce observations with simple single-power-law injection and scattering coefficients (scaling with rigidity R), similar to previous (non-dynamical) calculations. We also find: (1) The circumgalactic medium in realistic galaxies necessarily imposes an ~10 kpc CR scattering halo, influencing the required \u03bd(R). (2) Increasing the normalization of \u03bd(R) re-normalizes CR secondary spectra but also changes primary spectral slopes, owing to source distribution and loss effects. (3) Diffusive/turbulent reacceleration is unimportant and generally sub-dominant to gyroresonant/streaming losses, which are sub-dominant to adiabatic/convective terms dominated by ~ 1.0 - 1 turbulent/fountain motions. (4) CR spectra vary considerably across galaxies; certain features can arise from local structure rather than transport physics. (5) Systematic variation in CR ionization rates between LISM and molecular clouds (or Galactic position) arises naturally without invoking alternative sources. (6) Abundances of CNO nuclei require most CR acceleration occurs around when reverse shocks form in SNe, not in OB wind bubbles or later Sedov\u2013Taylor stages of SNe remnants.",
"doi": "10.1093/mnras/stac1791",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-11",
"series_number": "3",
"volume": "516",
"issue": "3",
"pages": "3470-3514"
},
{
"id": "authors:81zqk-s7b89",
"collection": "authors",
"collection_id": "81zqk-s7b89",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221024-123751900.6",
"type": "article",
"title": "Dust in the wind with resonant drag instabilities \u2013 I. The dynamics of dust-driven outflows in GMCs and H\u026a\u026a regions",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Rosen",
"given_name": "Anna L.",
"orcid": "0000-0003-4423-0660",
"clpid": "Rosen-Anna-L"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-Jonathan"
},
{
"family_name": "Panopoulou",
"given_name": "Georgia V.",
"orcid": "0000-0001-7482-5759",
"clpid": "Panopoulou-Georgia-V"
},
{
"family_name": "Soliman",
"given_name": "Nadine H.",
"orcid": "0000-0002-6810-1110",
"clpid": "Soliman-Nadine-H"
},
{
"family_name": "Seligman",
"given_name": "Darryl",
"orcid": "0000-0002-0726-6480",
"clpid": "Seligman-Darryl"
},
{
"family_name": "Steinwandel",
"given_name": "Ulrich P.",
"orcid": "0000-0001-8867-5026",
"clpid": "Steinwandel-Ulrich-P"
}
],
"abstract": "Radiation-dust driven outflows, where radiation pressure on dust grains accelerates gas, occur in many astrophysical environments. Almost all previous numerical studies of these systems have assumed that the dust was perfectly coupled to the gas. However, it has recently been shown that the dust in these systems is unstable to a large class of 'resonant drag instabilities' (RDIs) which de-couple the dust and gas dynamics and could qualitatively change the non-linear outcome of these outflows. We present the first simulations of radiation-dust driven outflows in stratified, inhomogeneous media, including explicit grain dynamics and a realistic spectrum of grain sizes and charge, magnetic fields and Lorentz forces on grains (which dramatically enhance the RDIs), Coulomb and Epstein drag forces, and explicit radiation transport allowing for different grain absorption and scattering properties. In this paper, we consider conditions resembling giant molecular clouds (GMCs), H\u026a\u026a regions, and distributed starbursts, where optical depths are modest (\u22721), single-scattering effects dominate radiation-dust coupling, Lorentz forces dominate over drag on grains, and the fastest-growing RDIs are similar, such as magnetosonic and fast-gyro RDIs. These RDIs generically produce strong size-dependent dust clustering, growing non-linear on time-scales that are much shorter than the characteristic times of the outflow. The instabilities produce filamentary and plume-like or 'horsehead' nebular morphologies that are remarkably similar to observed dust structures in GMCs and H\u026a\u026a regions. Additionally, in some cases they strongly alter the magnetic field structure and topology relative to filaments. Despite driving strong micro-scale dust clumping which leaves some gas 'behind,' an order-unity fraction of the gas is always efficiently entrained by dust.",
"doi": "10.1093/mnras/stac1784",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-11",
"series_number": "1",
"volume": "517",
"issue": "1",
"pages": "1491-1517"
},
{
"id": "authors:k18n5-j9w97",
"collection": "authors",
"collection_id": "k18n5-j9w97",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221024-125854800.20",
"type": "article",
"title": "The impact of cosmic rays on dynamical balance and disc\u2013halo interaction in L\u22c6 disc galaxies",
"author": [
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Gurvich",
"given_name": "Alexander B.",
"orcid": "0000-0002-6145-3674",
"clpid": "Gurvich-Alexander-B"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Trapp",
"given_name": "Cameron",
"orcid": "0000-0001-7813-0268",
"clpid": "Trapp-Cameron"
},
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
}
],
"abstract": "Cosmic rays (CRs) are an important component in the interstellar medium, but their effect on the dynamics of the disc\u2013halo interface (<10 kpc from the disc) is still unclear. We study the influence of CRs on the gas above the disc with high-resolution FIRE-2 cosmological simulations of late-type L\u22c6 galaxies at redshift z \u223c 0. We compare runs with and without CR feedback (with constant anisotropic diffusion \u03ba_\u2225 \u223c 3 \u00d7 10\u00b2\u2079 cm2\u2009s\u207b\u00b9 and streaming). Our simulations capture the relevant disc\u2013halo interactions, including outflows, inflows, and galactic fountains. Extra-planar gas in all of the runs satisfies dynamical balance, where total pressure balances the weight of the overlying gas. While the kinetic pressure from non-uniform motion (\u22731\u2009kpc scale) dominates in the mid-plane, thermal and bulk pressures (or CR pressure if included) take over at large heights. We find that with CR feedback, (1) the warm (\u223c10\u2074 K) gas is slowly accelerated by CRs; (2) the hot (>5 \u00d7 10\u2075 K) gas scale height is suppressed; (3) the warm-hot (2 \u00d7 10\u2074 - 5 \u00d7 10\u2075 K) medium becomes the most volume-filling phase in the disc\u2013halo interface. We develop a novel conceptual model of the near-disc gas dynamics in low-redshift L\u22c6 galaxies: with CRs, the disc\u2013halo interface is filled with CR-driven warm winds and hot superbubbles that are propagating into the circumgalactic medium with a small fraction falling back to the disc. Without CRs, most outflows from hot superbubbles are trapped by the existing hot halo and gravity, so typically they form galactic fountains.",
"doi": "10.1093/mnras/stac2236",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-10-07",
"series_number": "1",
"volume": "517",
"issue": "1",
"pages": "597-615"
},
{
"id": "authors:bbt2w-rtz56",
"collection": "authors",
"collection_id": "bbt2w-rtz56",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221017-12657600.19",
"type": "article",
"title": "Establishing Dust Rings and Forming Planets within Them",
"author": [
{
"family_name": "Lee",
"given_name": "Eve J.",
"orcid": "0000-0002-1228-9820",
"clpid": "Lee-Eve-J"
},
{
"family_name": "Fuentes",
"given_name": "J. R.",
"orcid": "0000-0003-2124-9764",
"clpid": "Fuentes-Jos\u00e9-Rafael"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Radio images of protoplanetary disks demonstrate that dust grains tend to organize themselves into rings. These rings may be a consequence of dust trapping within gas pressure maxima, wherein the local high dust-to-gas ratio is expected to trigger the formation of planetesimals and eventually planets. We revisit the behavior of dust near gas pressure perturbations enforced by a planet in two-dimensional, shearing-box simulations. While dust grains collect into generally long-lived rings, particles with a small Stokes parameter \u03c4\u209b < 0.1 tend to advect out of the ring within a few drift timescales. Scaled to the properties of ALMA disks, we find that rings composed of larger particles (\u03c4\u209b \u2265 0.1) can nucleate a dust clump massive enough to trigger pebble accretion, which proceeds to ingest the entire dust ring well within \u223c1 Myr. To ensure the survival of the dust rings, we favor a nonplanetary origin and typical grain size \u03c4\u209b \u2272 0.05\u20130.1. Planet-driven rings may still be possible but if so we would expect the orbital distance of the dust rings to be larger for older systems.",
"doi": "10.3847/1538-4357/ac8cfe",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2022-10-01",
"series_number": "2",
"volume": "937",
"issue": "2",
"pages": "Art. No. 95"
},
{
"id": "authors:7tfnz-nrj74",
"collection": "authors",
"collection_id": "7tfnz-nrj74",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220926-576716400.13",
"type": "article",
"title": "Shapes of Milky-Way-mass galaxies with self-interacting dark matter",
"author": [
{
"family_name": "Vargya",
"given_name": "Drona",
"clpid": "Vargya-Drona"
},
{
"family_name": "Sanderson",
"given_name": "Robyn",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-Robyn-E"
},
{
"family_name": "Sameie",
"given_name": "Omid",
"orcid": "0000-0003-4394-6085",
"clpid": "Sameie-Omid"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Graus",
"given_name": "Andrew",
"clpid": "Graus-Andrew-S"
}
],
"abstract": "Self-interacting dark matter (SIDM) models offer one way to reconcile inconsistencies between observations and predictions from collisionless cold dark matter (CDM) models on dwarf-galaxy scales. In order to incorporate the effects of both baryonic and SIDM interactions, we study a suite of cosmological-baryonic simulations of Milky-Way (MW)-mass galaxies from the Feedback in Realistic Environments (FIRE-2) project where we vary the SIDM self-interaction cross-section\u00a0\u03c3/m. We compare the shape of the main dark matter (DM) halo at redshift z\u00a0= 0 predicted by SIDM simulations (at \u03c3/m\u00a0= 0.1, 1, and 10\u00a0cm\u00b2\u2009g\u207b\u00b9) with CDM simulations using the same initial conditions. In the presence of baryonic feedback effects, we find that SIDM models do not produce the large differences in the inner structure of MW-mass galaxies predicted by SIDM-only models. However, we do find that the radius where the shape of the total mass distribution begins to differ from that of the stellar mass distribution is dependent on \u03c3/m. This transition could potentially be used to set limits on the SIDM cross-section\u00a0in the MW.",
"doi": "10.1093/mnras/stac2069",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-10",
"series_number": "2",
"volume": "516",
"issue": "2",
"pages": "2389-2405"
},
{
"id": "authors:6jz2g-q4p08",
"collection": "authors",
"collection_id": "6jz2g-q4p08",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20221010-454096500.11",
"type": "article",
"title": "Magnetic fields on FIRE: Comparing B-fields in the multiphase ISM and CGM of simulated L\u22c6 galaxies to observations",
"author": [
{
"family_name": "Ponnada",
"given_name": "Sam B.",
"orcid": "0000-0002-7484-2695",
"clpid": "Ponnada-Sam-B"
},
{
"family_name": "Panopoulou",
"given_name": "Georgia V.",
"orcid": "0000-0001-7482-5759",
"clpid": "Panopoulou-Georgia-V"
},
{
"family_name": "Butsky",
"given_name": "Iryna S.",
"orcid": "0000-0003-1257-5007",
"clpid": "Butsky-Iryna-S"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Loebman",
"given_name": "Sarah R.",
"orcid": "0000-0003-3217-5967",
"clpid": "Loebman-Sarah-R"
},
{
"family_name": "Hummels",
"given_name": "Cameron",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron-B"
},
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
}
],
"abstract": "The physics of magnetic fields (B) and cosmic rays (CRs) have recently been included in simulations of galaxy formation. However, significant uncertainties remain in how these components affect galaxy evolution. To understand their common observational tracers, we analyse the magnetic fields in a set of high-resolution, magnetohydrodynamic, cosmological simulations of Milky-Way-like galaxies from the FIRE-2 project. We compare mock observables of magnetic field tracers for simulations with and without CRs to observations of Zeeman splitting and rotation/dispersion measures. We find reasonable agreement between simulations and observations in both the neutral and the ionized interstellar medium (ISM). We find that the simulated galaxies with CRs show weaker ISM |B| fields on average compared to their magnetic-field-only counterparts. This is a manifestation of the effects of CRs in the diffuse, low density inner circumgalactic medium (CGM). We find that equipartition between magnetic and cosmic ray energy densities may be valid at large (> 1\u2009kpc) scales for typical ISM densities of Milky-Way-like galaxies, but not in their haloes. Within the ISM, the magnetic fields in our simulated galaxies follow a power-law scaling with gas density. The scaling extends down to neutral hydrogen number densities < 300\u00a0cm\u207b\u00b3, in contrast to observationally derived models, but consistent with the observational measurements. Finally, we generate synthetic rotation measure (RM) profiles for projections of the simulated galaxies and compare to observational constraints in the CGM. While consistent with upper limits, improved data are needed to detect the predicted CGM RMs at 10\u2013200\u00a0kpc and better constrain theoretical predictions.",
"doi": "10.1093/mnras/stac2448",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-09-22",
"series_number": "3",
"volume": "516",
"issue": "3",
"pages": "4417-4431"
},
{
"id": "authors:w4dyv-ywb55",
"collection": "authors",
"collection_id": "w4dyv-ywb55",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220923-941669700.9",
"type": "article",
"title": "Exploring metallicity-dependent rates of Type Ia supernovae and their impact on galaxy formation",
"author": [
{
"family_name": "Gandhi",
"given_name": "Pratik J.",
"orcid": "0000-0003-0965-605X",
"clpid": "Gandhi-Pratik-J"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Shappee",
"given_name": "Benjamin J.",
"orcid": "0000-0003-4631-1149",
"clpid": "Shappee-B-J"
},
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-Coral"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
}
],
"abstract": "Type Ia supernovae are critical for feedback and elemental enrichment in galaxies. Recent surveys like the All-Sky Automated Survey for Supernova (ASAS-SN) and the Dark Energy Survey (DES) find that the specific supernova Ia rate at z \u223c 0 may be \u227220\u201350\u00d7 higher in lower mass galaxies than at Milky Way-mass. Independently, observations show that the close-binary fraction of solar-type Milky Way stars is higher at lower metallicity. Motivated by these observations, we use the FIRE-2 cosmological zoom-in simulations to explore the impact of metallicity-dependent rate models on galaxies of M_* ~ 10\u2077-10\u00b9\u00b9M_\u2299. First, we benchmark our simulated star formation histories against observations, and show that the assumed stellar mass functions play a major role in determining the degree of tension between observations and metallicity-independent rate models, potentially causing ASAS-SN and DES observations to agree more than might appear. Models in which the supernova Ia rate increases with decreasing metallicity (\u221d Z\u207b\u2070\u1427\u2075 \u1d57\u1d52 \u207b\u00b9) provide significantly better agreement with observations. Encouragingly, these rate increases (\u227310\u00d7 in low-mass galaxies) do not significantly impact galaxy masses and morphologies, which remain largely unaffected except for our most extreme models. We explore implications for both [Fe/H] and [\u03b1/Fe] enrichment; metallicity-dependent rate models can improve agreement with the observed stellar mass\u2013metallicity relations in low-mass galaxies. Our results demonstrate that a range of metallicity-dependent rate models are viable for galaxy formation and motivate future work.",
"doi": "10.1093/mnras/stac2228",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-09-07",
"series_number": "2",
"volume": "516",
"issue": "2",
"pages": "1941-1958"
},
{
"id": "authors:vh5ty-61002",
"collection": "authors",
"collection_id": "vh5ty-61002",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220825-833695900.765",
"type": "article",
"title": "The observability of galaxy merger signatures in nearby gas-rich spirals",
"author": [
{
"family_name": "McElroy",
"given_name": "Rebecca",
"orcid": "0000-0003-2290-7060",
"clpid": "McElroy-Rebecca"
},
{
"family_name": "Bottrell",
"given_name": "Connor",
"orcid": "0000-0003-4758-4501",
"clpid": "Bottrell-Connor"
},
{
"family_name": "Hani",
"given_name": "Maan H.",
"orcid": "0000-0002-5351-2291",
"clpid": "Hani-Maan-H"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232",
"clpid": "Moreno-Jorge"
},
{
"family_name": "Croom",
"given_name": "Scott M.",
"orcid": "0000-0003-2880-9197",
"clpid": "Croom-Scott-M"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Twum",
"given_name": "Angela",
"clpid": "Twum-Angela"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-Lars"
},
{
"family_name": "Husemann",
"given_name": "Bernd",
"orcid": "0000-0003-2901-6842",
"clpid": "Husemann-Bernd"
}
],
"abstract": "Galaxy mergers are crucial to understanding galaxy evolution, therefore we must determine their observational signatures to select them from large IFU galaxy samples such as MUSE and SAMI. We employ 24 high-resolution idealized hydrodynamical galaxy merger simulations based on the 'Feedback In Realistic Environment' (FIRE-2) model to determine the observability of mergers to various configurations and stages using synthetic images and velocity maps. Our mergers cover a range of orbital configurations at fixed 1:2.5 stellar mass ratio for two gas rich spirals at low redshift. Morphological and kinematic asymmetries are computed for synthetic images and velocity maps spanning each interaction. We divide the interaction sequence into three: (1) the pair phase; (2) the merging phase; and (3) the post-coalescence phase. We correctly identify mergers between first pericentre passage and 500\u00a0Myr after coalescence using kinematic asymmetry with 66\u00a0per\u2009cent completeness, depending upon merger phase and the field of view of the observation. We detect fewer mergers in the pair phase (40\u00a0per\u2009cent) and many more in the merging and post-coalescence phases (97\u00a0per\u2009cent). We find that merger detectability decreases with field of view, except in retrograde mergers, where centrally concentrated asymmetric kinematic features enhances their detectability. Using a cut-off derived from a combination of photometric and kinematic asymmetry, we increase these detections to 89\u00a0per\u2009cent overall, 79\u00a0per\u2009cent in pairs, and close to 100\u00a0per\u2009cent in the merging and post-coalescent phases. By using this combined asymmetry cut-off we mitigate some of the effects caused by smaller fields of view subtended by massively multiplexed integral field spectroscopy programmes.",
"doi": "10.1093/mnras/stac1715",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-09",
"series_number": "3",
"volume": "515",
"issue": "3",
"pages": "3406-3419"
},
{
"id": "authors:3g0w5-5k886",
"collection": "authors",
"collection_id": "3g0w5-5k886",
"cite_using_url": "https://authors.library.caltech.edu/records/3g0w5-5k886",
"type": "article",
"title": "Gusts in the headwind: uncertainties in direct dark matter detection",
"author": [
{
"family_name": "Lawrence",
"given_name": "Grace E",
"orcid": "0000-0001-5164-8569"
},
{
"family_name": "Duffy",
"given_name": "Alan R",
"orcid": "0000-0002-9636-1809"
},
{
"family_name": "Blake",
"given_name": "Chris A"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We use high-resolution, hydrodynamic, galaxy simulations from the Latte suite of FIRE-2 simulations to investigate the inherent variation of dark matter in sub-sampled regions around the Solar Circle of a Milky Way-type analogue galaxy and its impact on direct dark matter detection. These simulations show that the baryonic back reaction, as well as the assembly history of substructures, has lasting impacts on the dark matter's spatial and velocity distributions. These are experienced as 'gusts' of dark matter wind around the Solar Circle, potentially complicating interpretations of direct detection experiments on Earth. We find that the velocity distribution function in the galactocentric frame shows strong deviations from the Maxwell Boltzmann form typically assumed in the fiducial Standard Halo Model, indicating the presence of high-velocity substructures. By introducing a new numerical integration technique that removes any dependencies on the Standard Halo Model, we generate event-rate predictions for both single-element Germanium and compound Sodium Iodide detectors, and explore how the variability of dark matter around the Solar Circle influences annual modulation signal predictions. We find that these velocity substructures contribute additional astrophysical uncertainty to the interpretation of event rates, although their impact on summary statistics, such as the peak day of annual modulation, is generally low.
",
"doi": "10.1093/mnras/stac2447",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-09",
"series_number": "2",
"volume": "524",
"issue": "2",
"pages": "2606-2623"
},
{
"id": "authors:63ntk-kn633",
"collection": "authors",
"collection_id": "63ntk-kn633",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183312768",
"type": "article",
"title": "Cluster assembly and the origin of mass segregation in the STARFORGE simulations",
"author": [
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D\u00e1vid"
},
{
"family_name": "Markey",
"given_name": "Carleen",
"orcid": "0000-0003-0629-8840",
"clpid": "Markey-Carleen"
},
{
"family_name": "Offner",
"given_name": "Stella S. R.",
"orcid": "0000-0003-1252-9916",
"clpid": "Offner-Stella-S-R"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-Michael-Y"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Rosen",
"given_name": "Anna L.",
"orcid": "0000-0003-4423-0660",
"clpid": "Rosen-Anna-L"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Stars form in dense, clustered environments, where feedback from newly formed stars eventually ejects the gas, terminating star formation and leaving behind one or more star clusters. Using the STARFORGE simulations, it is possible to simulate this process in its entirety within a molecular cloud, while explicitly evolving the gas radiation and magnetic fields and following the formation of individual, low-mass stars. We find that individual star-formation sites merge to form ever larger structures, while still accreting gas. Thus clusters are assembled through a series of mergers. During the cluster assembly process, a small fraction of stars are ejected from their clusters; we find no significant difference between the mass distribution of the ejected stellar population and that of stars inside clusters. The star-formation sites that are the building blocks of clusters start out mass segregated with one or a few massive stars at their centre. As they merge the newly formed clusters maintain this feature, causing them to have mass-segregated substructures without themselves being centrally condensed. The merged clusters relax to a centrally condensed mass-segregated configuration through dynamical interactions between their members, but this process does not finish before feedback expels the remaining gas from the cluster. In the simulated runs, the gas-free clusters then become unbound and breakup. We find that turbulent driving and a periodic cloud geometry can significantly reduce clustering and prevent gas expulsion. Meanwhile, the initial surface density and level of turbulence have little qualitative effect on cluster evolution, despite the significantly different star formation histories.",
"doi": "10.1093/mnras/stac1737",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-09",
"series_number": "1",
"volume": "515",
"issue": "1",
"pages": "167-184"
},
{
"id": "authors:wp7tz-4fd02",
"collection": "authors",
"collection_id": "wp7tz-4fd02",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220817-927599000",
"type": "article",
"title": "Spatially resolved gas-phase metallicity in FIRE-2 dwarfs: late-time evolution of metallicity relations in simulations with feedback and mergers",
"author": [
{
"family_name": "Porter",
"given_name": "Lori E.",
"orcid": "0000-0002-7795-2267",
"clpid": "Porter-Lori-E"
},
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-Matthew-E"
},
{
"family_name": "Burkhart",
"given_name": "Blakesley",
"orcid": "0000-0001-5817-5944",
"clpid": "Burkhart-Blakesley"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Emerick",
"given_name": "Andrew",
"orcid": "0000-0003-2807-328X",
"clpid": "Emerick-Andrew"
}
],
"abstract": "We present an analysis of spatially resolved gas-phase metallicity relations in five dwarf galaxies (\u2060M\u2095\u2090\u2097\u2092 \u2248 10\u00b9\u00b9 M_\u2299\u2060, M\u22c6 \u2248 10^(8.8)\u221210^(9.6) M_\u2299\u2060) from the FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulation suite, which include an explicit model for sub-grid turbulent mixing of metals in gas, near z \u2248 0, over a period of 1.4 Gyr, and compare our findings with observations. While these dwarf galaxies represent a diverse sample, we find that all simulated galaxies match the observed mass\u2013metallicity (MZR) and mass\u2013metallicity gradient (MZGR) relations. We note that in all five galaxies, the metallicities are effectively identical between phases of the interstellar medium (ISM), with 95 per cent of the gas being within \u00b10.1 dex between the cold and dense gas (T < 500 K and n_H > 1 cm\u207b\u00b3), ionized gas (near the H\u03b1T \u2248 10\u2074 K ridge-line), and nebular regions (ionized gas where the 10 Myr-averaged star formation rate is non-zero). We find that most of the scatter in relative metallicity between cold dense gas and ionized gas/nebular regions can be attributed to either local starburst events or metal-poor inflows. We also note the presence of a major merger in one of our galaxies, m11e, with a substantial impact on the metallicity distribution in the spatially resolved map, showing two strong metallicity peaks and triggering a starburst in the main galaxy.",
"doi": "10.1093/mnras/stac1958",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-09",
"series_number": "3",
"volume": "515",
"issue": "3",
"pages": "3555-3576"
},
{
"id": "authors:qyjc4-vtq77",
"collection": "authors",
"collection_id": "qyjc4-vtq77",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220906-252653000",
"type": "article",
"title": "Effects of the environment and feedback physics on the initial mass function of stars in the STARFORGE simulations",
"author": [
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D\u00e1vid"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-Michael-Y"
},
{
"family_name": "Offner",
"given_name": "Stella S. R.",
"orcid": "0000-0003-1252-9916",
"clpid": "Offner-Stella-S-R"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Rosen",
"given_name": "Anna L.",
"orcid": "0000-0003-4423-0660",
"clpid": "Rosen-Anna-L"
}
],
"abstract": "One of the key mysteries of star formation is the origin of the stellar initial mass function (IMF). The IMF is observed to be nearly universal in the Milky Way and its satellites, and significant variations are only inferred in extreme environments, such as the cores of massive elliptical galaxies and the Central Molecular Zone. In this work, we present simulations from the STARFORGE project that are the first cloud-scale radiation-magnetohydrodynamic simulations that follow individual stars and include all relevant physical processes. The simulations include detailed gas thermodynamics, as well as stellar feedback in the form of protostellar jets, stellar radiation, winds, and supernovae. In this work, we focus on how stellar radiation, winds, and supernovae impact star-forming clouds. Radiative feedback plays a major role in quenching star formation and disrupting the cloud; however, the IMF peak is predominantly set by protostellar jet physics. We find that the effect of stellar winds is minor, and supernovae 'occur too late' to affect the IMF or quench star formation. We also investigate the effects of initial conditions on the IMF. We find that the IMF is insensitive to the initial turbulence, cloud mass, and cloud surface density, even though these parameters significantly shape the star formation history of the cloud, including the final star formation efficiency. Meanwhile, the characteristic stellar mass depends weakly on metallicity and the interstellar radiation field, which essentially set the average gas temperature. Finally, while turbulent driving and the level of magnetization strongly influence the star formation history, they only influence the high-mass slope of the IMF.",
"doi": "10.1093/mnras/stac2060",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-08-17",
"series_number": "4",
"volume": "515",
"issue": "4",
"pages": "4929-4952"
},
{
"id": "authors:bwr77-2t018",
"collection": "authors",
"collection_id": "bwr77-2t018",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220908-161233774",
"type": "article",
"title": "On the optical properties of resonant drag instabilities: variability of asymptotic giant branch and R Coronae Borealis stars",
"author": [
{
"family_name": "Steinwandel",
"given_name": "Ulrich P.",
"orcid": "0000-0001-8867-5026",
"clpid": "Steinwandel-Ulrich-P"
},
{
"family_name": "Kaurov",
"given_name": "Alexander A.",
"clpid": "Kaurov-Alexander-A"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-Jonathan"
}
],
"abstract": "In dusty cool-star outflow or ejection events around asymptotic giant branch (AGB) or R Coronae Borealis or RCB-like stars, dust is accelerated by radiation from the star and coupled to the gas via collisional drag forces. It has recently been shown that such dust-gas mixtures are unstable to a super-class of instabilities called the resonant drag instabilities (RDIs), which promote dust clustering. We therefore consider idealized simulations of the RDIs operating on a spectrum of dust grain sizes subject to radiative acceleration (allowing for different grain optical properties), coupled to the gas with a realistic drag law, including or excluding the effects of magnetic fields and charged grains, and calculate for the first time how the RDIs could contribute to observed variability. We show that the RDIs naturally produce significant variations (spatially and temporally) ($\\sim 10\\!-\\!20{{\\ \\rm per\\ cent}}$ 1\u2009\u03c3-level) in the extinction, corresponding to $\\sim 0.1\\!-\\!1\\,$mag level in the stellar types above, on time-scales of order months to a year. The fluctuations are surprisingly robust to the assumed size of the source as they are dominated by large-scale modes, which also means their spatial structure could be resolved in some nearby systems. We also quantify how this produces variations in the line-of-sight grain size-distribution. All of these variations are similar to those observed, suggesting that the RDIs may play a key role driving observed spatial and temporal variability in dust extinction within dusty outflow/ejection events around cool stars. We further propose that the measured variations in grain sizes could directly be used to identify the presence of the RDIs in close by systems with observations.",
"doi": "10.1093/mnras/stac2035",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-08-13",
"series_number": "4",
"volume": "515",
"issue": "4",
"pages": "4797-4809"
},
{
"id": "authors:wwmxh-bet24",
"collection": "authors",
"collection_id": "wwmxh-bet24",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183319490",
"type": "article",
"title": "The galactic dust-up: modelling dust evolution in FIRE",
"author": [
{
"family_name": "Choban",
"given_name": "Caleb R.",
"orcid": "0000-0001-9200-169X",
"clpid": "Choban-Caleb-R"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Sandstrom",
"given_name": "Karin M.",
"orcid": "0000-0002-4378-8534",
"clpid": "Sandstrom-Karin-M"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
}
],
"abstract": "Recent strides have been made developing dust evolution models for galaxy formation simulations but these approaches vary in their assumptions and degree of complexity. Here, we introduce and compare two separate dust evolution models (labelled 'Elemental' and 'Species'), based on recent approaches, incorporated into the GIZMO code and coupled with FIRE-2 stellar feedback and interstellar medium physics. Both models account for turbulent dust diffusion, stellar production of dust, dust growth via gas-dust accretion, and dust destruction from time-resolved supernovae, thermal sputtering in hot gas, and astration. The 'Elemental' model tracks the evolution of generalized dust species and utilizes a simple, 'tunable' dust growth routine, while the 'Species' model tracks the evolution of specific dust species with set chemical compositions and incorporates a physically motivated, two-phase dust growth routine. We test and compare these models in an idealized Milky Way-mass galaxy and find that while both produce reasonable galaxy-integrated dust-to-metals (D/Z) ratios and predict gas-dust accretion as the main dust growth mechanism, a chemically motivated model is needed to reproduce the observed scaling relation between individual element depletions and D/Z with column density and local gas density. We also find the inclusion of theoretical metallic iron and O-bearing dust species are needed in the case of specific dust species in order to match observations of O and Fe depletions, and the integration of a sub-resolution dense molecular gas/CO scheme is needed to both match observed C depletions and ensure carbonaceous dust is not overproduced in dense environments.",
"doi": "10.1093/mnras/stac1542",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-08",
"series_number": "3",
"volume": "514",
"issue": "3",
"pages": "4506-4534"
},
{
"id": "authors:2tfde-9m062",
"collection": "authors",
"collection_id": "2tfde-9m062",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183316128",
"type": "article",
"title": "Hot-mode accretion and the physics of thin-disc galaxy formation",
"author": [
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565",
"clpid": "Stern-Jonathan"
},
{
"family_name": "Bullock",
"given_name": "James",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Gurvich",
"given_name": "Alexander B.",
"orcid": "0000-0002-6145-3674",
"clpid": "Gurvich-Alexander-B"
},
{
"family_name": "Yu",
"given_name": "Sijie",
"orcid": "0000-0002-1019-0341",
"clpid": "Yu-Sijie"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Fielding",
"given_name": "Drummond B.",
"orcid": "0000-0003-3806-8548",
"clpid": "Fielding-Drummond-B"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Starkenburg",
"given_name": "Tjitske",
"orcid": "0000-0003-2539-8206",
"clpid": "Starkenburg-Tjitske"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232",
"clpid": "Moreno-Jorge"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Trapp",
"given_name": "Cameron",
"orcid": "0000-0001-7813-0268",
"clpid": "Trapp-Cameron"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We use FIRE simulations to study disc formation in z \u223c 0, Milky Way-mass galaxies, and conclude that a key ingredient for the formation of thin stellar discs is the ability for accreting gas to develop an aligned angular momentum distribution via internal cancellation prior to joining the galaxy. Among galaxies with a high fraction (\u2060>70 per cent\u2060) of their young stars in a thin disc (h/R \u223c 0.1), we find that: (i) hot, virial-temperature gas dominates the inflowing gas mass on halo scales (\u227320 kpc), with radiative losses offset by compression heating; (ii) this hot accretion proceeds until angular momentum support slows inward motion, at which point the gas cools to \u227210\u2074K\u2060; (iii) prior to cooling, the accreting gas develops an angular momentum distribution that is aligned with the galaxy disc, and while cooling transitions from a quasi-spherical spatial configuration to a more-flattened, disc-like configuration. We show that the existence of this 'rotating cooling flow' accretion mode is strongly correlated with the fraction of stars forming in a thin disc, using a sample of 17 z \u223c 0 galaxies spanning a halo mass range of 10^(10.5) M\u2299 \u2272 M_h \u2272 10\u00b9\u00b2 M\u2299 and stellar mass range of 10\u2078 M\u2299 \u2272 M\u22c6 \u2272 10\u00b9\u00b9 M\u2299. Notably, galaxies with a thick disc or irregular morphology do not undergo significant angular momentum alignment of gas prior to accretion and show no correspondence between halo gas cooling and flattening. Our results suggest that rotating cooling flows (or, more generally, rotating subsonic flows) that become coherent and angular momentum-supported prior to accretion on to the galaxy are likely a necessary condition for the formation of thin, star-forming disc galaxies in a \u039bCDM universe.",
"doi": "10.1093/mnras/stac1603",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-08",
"series_number": "4",
"volume": "514",
"issue": "4",
"pages": "5056-5073"
},
{
"id": "authors:51fpx-1hd76",
"collection": "authors",
"collection_id": "51fpx-1hd76",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183245280",
"type": "article",
"title": "The In Situ Origins of Dwarf Stellar Outskirts in FIRE-2",
"author": [
{
"family_name": "Kado-Fong",
"given_name": "Erin",
"orcid": "0000-0002-0332-177X",
"clpid": "Kado-Fong-Erin"
},
{
"family_name": "Sanderson",
"given_name": "Robyn E.",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-Robyn-E"
},
{
"family_name": "Greene",
"given_name": "Jenny E.",
"orcid": "0000-0002-5612-3427",
"clpid": "Greene-Jenny-E"
},
{
"family_name": "Cunningham",
"given_name": "Emily C.",
"orcid": "0000-0002-6993-0826",
"clpid": "Cunningham-Emily-C"
},
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-Coral-R"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Huang",
"given_name": "Song",
"orcid": "0000-0003-1385-7591",
"clpid": "Huang-Song"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Starkenburg",
"given_name": "Tjitske",
"orcid": "0000-0003-2539-8206",
"clpid": "Starkenburg-Tjitske"
}
],
"abstract": "Extended, old, and round stellar halos appear to be ubiquitous around high-mass dwarf galaxies (10^(8.5) < M_\u22c6/M_\u2299 < 10^(9.6)) in the observed universe. However, it is unlikely that these dwarfs have undergone a sufficient number of minor mergers to form stellar halos that are composed of predominantly accreted stars. Here, we demonstrate that FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulations are capable of producing dwarf galaxies with realistic structures, including both a thick disk and round stellar halo. Crucially, these stellar halos are formed in situ, largely via the outward migration of disk stars. However, there also exists a large population of \"nondisky\" dwarfs in FIRE-2 that lack a well-defined disk/halo and do not resemble the observed dwarf population. These nondisky dwarfs tend to be either more gas-poor or to have burstier recent star formation histories than the disky dwarfs, suggesting that star formation feedback may be preventing disk formation. Both classes of dwarfs underscore the power of a galaxy's intrinsic shape\u2014which is a direct quantification of the distribution of the galaxy's stellar content\u2014to interrogate the feedback implementation in simulated galaxies.",
"doi": "10.3847/1538-4357/ac6c88",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2022-06-01",
"series_number": "2",
"volume": "931",
"issue": "2",
"pages": "Art. No. 152"
},
{
"id": "authors:fbhjz-hvp06",
"collection": "authors",
"collection_id": "fbhjz-hvp06",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220525-91487000",
"type": "article",
"title": "Amplified J-factors in the Galactic Centre for velocity-dependent dark matter annihilation in FIRE simulations",
"author": [
{
"family_name": "McKeown",
"given_name": "Daniel",
"orcid": "0000-0002-5121-7117",
"clpid": "McKeown-Daniel"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Mercado",
"given_name": "Francisco J.",
"orcid": "0000-0002-5908-737X",
"clpid": "Mercado-Francisco-J"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Necib",
"given_name": "Lina",
"orcid": "0000-0003-2806-1414",
"clpid": "Necib-Lina"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Yu",
"given_name": "Sijie",
"orcid": "0000-0002-1019-0341",
"clpid": "Yu-Sijie"
}
],
"abstract": "We use FIRE-2 zoom cosmological simulations of Milky Way size Galaxy haloes to calculate astrophysical J-factors for dark matter annihilation and indirect detection studies. In addition to velocity-independent (s-wave) annihilation cross-sections\u00a0\u3008\u03c3v\u3009, we also calculate effective J-factors for velocity-dependent models, where the annihilation cross-section\u00a0is either p-wave (\u221d\u00a0v\u00b2/c\u00b2) or d-wave (\u221d\u00a0v\u2074/c\u2074). We use 12 pairs of simulations, each run with dark matter-only (DMO) physics and FIRE-2 physics. We observe FIRE runs produce central dark matter velocity dispersions that are systematically larger than in DMO runs by factors of \u223c2.5\u20134. They also have a larger range of central (\u223c400\u00a0pc) dark matter densities than the DMO runs (\u03c1_(FIRE)/\u03c1_(DMO) \u2243 0.5\u20133) owing to the competing effects of baryonic contraction and feedback. At 3 deg from the Galactic Centre, FIRE J-factors are 3\u201360 (p-wave) and 10\u2013500 (d-wave) times higher than in the DMO runs. The change in s-wave signal at 3 deg is more modest and can be higher or lower (\u223c0.3\u20137), though the shape of the emission profile is flatter (less peaked towards the Galactic Centre) and more circular on the sky in FIRE runs. Our results for s-wave are broadly consistent with the range of assumptions in most indirect detection studies. We observe p-wave J-factors that are significantly enhanced compared to most past estimates. We find that thermal models with p-wave annihilation may be within range of detection in the near future.",
"doi": "10.1093/mnras/stac966",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-06",
"series_number": "1",
"volume": "513",
"issue": "1",
"pages": "55-70"
},
{
"id": "authors:bef8d-mtw14",
"collection": "authors",
"collection_id": "bef8d-mtw14",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183305395",
"type": "article",
"title": "Numerical study of cosmic ray confinement through dust resonant drag instabilities",
"author": [
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-Jonathan"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We investigate the possibility of cosmic ray (CR) confinement by charged dust grains through resonant drag instabilities (RDIs). We perform magnetohydrodynamic particle-in-cell simulations of magnetized gas mixed with charged dust and cosmic rays, with the gyro-radii of dust and GeV CRs on \u223cau scales fully resolved. As a first study, we focus on one type of RDI wherein charged grains drift super-Alfv\u00e9nically, with Lorentz forces strongly dominating over drag forces. Dust grains are unstable to the RDIs and form concentrated columns and sheets, whose scale grows until saturating at the simulation box size. Initially perfectly streaming CRs are strongly scattered by RDI-excited Alfv\u00e9n waves, with the growth rate of the CR perpendicular velocity components equaling the growth rate of magnetic field perturbations. These rates are well-predicted by analytic linear theory. CRs finally become isotropized and drift at least at \u223cv_A by unidirectional Alfv\u00e9n waves excited by the RDIs, with a uniform distribution of the pitch angle cosine \u03bc and a flat profile of the CR pitch angle diffusion coefficient D_(\u03bc\u03bc) around \u03bc = 0, without the '90\u25cb pitch angle problem.' With CR feedback on the gas included, D_(\u03bc\u03bc) decreases by a factor of a few, indicating a lower CR scattering rate, because the backreaction on the RDI from the CR pressure adds extra wave damping, leading to lower quasi-steady-state scattering rates. Our study demonstrates that the dust-induced CR confinement can be very important under certain conditions, e.g. the dusty circumgalactic medium around quasars or superluminous galaxies.",
"doi": "10.1093/mnras/stac895",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-06",
"series_number": "1",
"volume": "513",
"issue": "1",
"pages": "282-295"
},
{
"id": "authors:weaaa-csc41",
"collection": "authors",
"collection_id": "weaaa-csc41",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220215-354905400",
"type": "article",
"title": "Galaxies lacking dark matter produced by close encounters in a cosmological simulation",
"author": [
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232",
"clpid": "Moreno-Jorge"
},
{
"family_name": "Danieli",
"given_name": "Shany",
"orcid": "0000-0002-1841-2252",
"clpid": "Danieli-Shany"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "\u00c7atmabacak",
"given_name": "Onur",
"orcid": "0000-0003-4067-1434",
"clpid": "\u00c7atmabacak-Onur"
},
{
"family_name": "Gurvich",
"given_name": "Alexander",
"orcid": "0000-0002-6145-3674",
"clpid": "Gurvich-Alexander-B"
},
{
"family_name": "Lazar",
"given_name": "Alexandres",
"orcid": "0000-0002-6852-6282",
"clpid": "Lazar-Alexandres"
},
{
"family_name": "Klein",
"given_name": "Courtney",
"orcid": "0000-0002-2762-4046",
"clpid": "Klein-Courtney"
},
{
"family_name": "Hummels",
"given_name": "Cameron B.",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron-B"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary"
},
{
"family_name": "Mercado",
"given_name": "Francisco J.",
"orcid": "0000-0002-5908-737X",
"clpid": "Mercado-Francisco-J"
},
{
"family_name": "Yu",
"given_name": "Sijie",
"orcid": "0000-0002-1019-0341",
"clpid": "Yu-Sijie"
},
{
"family_name": "Jiang",
"given_name": "Fangzhou",
"orcid": "0000-0001-6115-0633",
"clpid": "Jiang-Fangzhou"
},
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-Coral-R"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
}
],
"abstract": "The standard cold dark matter plus cosmological constant model predicts that galaxies form within dark-matter haloes, and that low-mass galaxies are more dark-matter dominated than massive ones. The unexpected discovery of two low-mass galaxies lacking dark matter immediately provoked concerns about the standard cosmology and ignited explorations of alternatives, including self-interacting dark matter and modified gravity. Apprehension grew after several cosmological simulations using the conventional model failed to form adequate numerical analogues with comparable internal characteristics (stellar masses, sizes, velocity dispersions and morphologies). Here we show that the standard paradigm naturally produces galaxies lacking dark matter with internal characteristics in agreement with observations. Using a state-of-the-art cosmological simulation and a meticulous galaxy-identification technique, we find that extreme close encounters with massive neighbours can be responsible for this. We predict that ~30% of massive central galaxies (with at least 10\u00b9\u00b9 solar masses in stars) harbour at least one dark-matter-deficient satellite (with 10\u2078\u201310\u2079 solar masses in stars). This distinctive class of galaxies provides an additional layer in our understanding of the role of interactions in shaping galactic properties. Future observations surveying galaxies in the aforementioned regime will provide a crucial test of this scenario.",
"doi": "10.1038/s41550-021-01598-4",
"issn": "2397-3366",
"publisher": "Nature Publishing Group",
"publication": "Nature Astronomy",
"publication_date": "2022-04",
"series_number": "4",
"volume": "6",
"issue": "4",
"pages": "496-502"
},
{
"id": "authors:b7zn7-fed21",
"collection": "authors",
"collection_id": "b7zn7-fed21",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220309-966983000",
"type": "article",
"title": "Black hole-galaxy scaling relations in FIRE: the importance of black hole location and mergers",
"author": [
{
"family_name": "\u00c7atmabacak",
"given_name": "Onur",
"orcid": "0000-0003-4067-1434",
"clpid": "\u00c7atmabacak-Onur"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
}
],
"abstract": "The concurrent growth of supermassive black holes (SMBHs) and their host galaxies remains to be fully explored, especially at high redshift. While often understood as a consequence of self-regulation via AGN feedback, it can also be explained by alternative SMBH accretion models. Here, we expand on previous work by studying the growth of SMBHs with the help of a large suite of cosmological zoom-in simulations (MassiveFIRE) that are part of the Feedback in Realistic Environments (FIRE) project. The growth of SMBHs is modelled in post-processing with different black hole accretion models, placements, and merger treatments, and validated by comparing to on-the-fly calculations. Scaling relations predicted by the gravitational torque-driven accretion (GTDA) model agree with observations at low redshift without the need for AGN feedback, in contrast to models in which the accretion rate depends strongly on SMBH mass. At high redshift, we find deviations from the local scaling relations in line with previous theoretical results. In particular, SMBHs are undermassive, presumably due to stellar feedback, but start to grow efficiently once their host galaxies reach M* \u223c 10\u00b9\u2070 M_\u2299. We analyse and explain these findings in the context of a simple analytic model. Finally, we show that the predicted scaling relations depend sensitively on the SMBH location and the efficiency of SMBH merging, particularly in low-mass systems. These findings highlight the relevance of understanding the evolution of SMBH-galaxy scaling relations to predict the rate of gravitational wave signals from SMBH mergers across cosmic history.",
"doi": "10.1093/mnras/stac040",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-03",
"series_number": "1",
"volume": "511",
"issue": "1",
"pages": "506-535"
},
{
"id": "authors:jz8ab-kfq94",
"collection": "authors",
"collection_id": "jz8ab-kfq94",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220223-919288000",
"type": "article",
"title": "Probing Hot Gas Components of the Circumgalactic Medium in Cosmological Simulations with the Thermal Sunyaev\u2013Zel'dovich Effect",
"author": [
{
"family_name": "Kim",
"given_name": "Junhan",
"orcid": "0000-0002-4274-9373",
"clpid": "Kim-Junhan"
},
{
"family_name": "Golwala",
"given_name": "Sunil",
"orcid": "0000-0002-1098-7174",
"clpid": "Golwala-S-R"
},
{
"family_name": "Bartlett",
"given_name": "James G.",
"orcid": "0000-0002-0303-3583",
"clpid": "Bartlett-James-G"
},
{
"family_name": "Amodeo",
"given_name": "Stefania",
"orcid": "0000-0002-4200-9965",
"clpid": "Amodeo-Stefania"
},
{
"family_name": "Battaglia",
"given_name": "Nicholas",
"orcid": "0000-0001-5846-0411",
"clpid": "Battaglia-Nicholas"
},
{
"family_name": "Benson",
"given_name": "Andrew J.",
"orcid": "0000-0001-5501-6008",
"clpid": "Benson-Andrew-J"
},
{
"family_name": "Hill",
"given_name": "J. Colin",
"orcid": "0000-0002-9539-0835",
"clpid": "Hill-J-Colin"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hummels",
"given_name": "Cameron B.",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron-B"
},
{
"family_name": "Moser",
"given_name": "Emily",
"orcid": "0000-0003-1593-1505",
"clpid": "Moser-Emily"
},
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-Matthew-E"
}
],
"abstract": "The thermal Sunyaev\u2013Zel'dovich (tSZ) effect is a powerful tool with the potential for constraining directly the properties of the hot gas that dominates dark matter halos because it measures pressure and thus thermal energy density. Studying this hot component of the circumgalactic medium (CGM) is important because it is strongly impacted by star formation and active galactic nucleus (AGN) activity in galaxies, participating in the feedback loop that regulates star and black hole mass growth in galaxies. We study the tSZ effect across a wide halo-mass range using three cosmological hydrodynamical simulations: Illustris-TNG, EAGLE, and FIRE-2. Specifically, we present the scaling relation between the tSZ signal and halo mass and the (mass-weighted) radial profiles of gas density, temperature, and pressure for all three simulations. The analysis includes comparisons to Planck tSZ observations and to the thermal pressure profile inferred from the Atacama Cosmology Telescope (ACT) measurements. We compare these tSZ data to simulations to interpret the measurements in terms of feedback and accretion processes in the CGM. We also identify as-yet unobserved potential signatures of these processes that may be visible in future measurements, which will have the capability of measuring tSZ signals to even lower masses. We also perform internal comparisons between runs with different physical assumptions. We conclude (1) there is strong evidence for the impact of feedback at R\u2085\u2080\u2080, but that this impact decreases by 5R\u2085\u2080\u2080, and (2) the thermodynamic profiles of the CGM are highly dependent on the implemented model, such as cosmic-ray or AGN feedback prescriptions.",
"doi": "10.3847/1538-4357/ac4750",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2022-02-20",
"series_number": "2",
"volume": "926",
"issue": "2",
"pages": "Art. No. 179"
},
{
"id": "authors:zjz4h-mm837",
"collection": "authors",
"collection_id": "zjz4h-mm837",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-619611000",
"type": "article",
"title": "The acoustic resonant drag instability with a spectrum of grain sizes",
"author": [
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-Jonathan"
},
{
"family_name": "Moroianu",
"given_name": "Stefania",
"clpid": "Moroianu-Stefania"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We study the linear growth and non-linear saturation of the 'acoustic Resonant Drag Instability' (RDI) when the dust grains, which drive the instability, have a wide, continuous spectrum of different sizes. This physics is generally applicable to dusty winds driven by radiation pressure, such as occurs around red-giant stars, star-forming regions, or active galactic nuclei. Depending on the physical size of the grains compared to the wavelength of the radiation field that drives the wind, two qualitatively different regimes emerge. In the case of grains that are larger than the radiation's wavelength \u2013 termed the constant-drift regime \u2013 the grain's equilibrium drift velocity through the gas is approximately independent of grain size, leading to strong correlations between differently sized grains that persist well into the saturated non-linear turbulence. For grains that are smaller than the radiation's wavelength \u2013 termed the non-constant-drift regime \u2013 the linear instability grows more slowly than the single-grain-size RDI and only the larger grains exhibit RDI-like behaviour in the saturated state. A detailed study of grain clumping and grain\u2013grain collisions shows that outflows in the constant-drift regime may be effective sites for grain growth through collisions, with large collision rates but low collision velocities.",
"doi": "10.1093/mnras/stab3377",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-02",
"series_number": "1",
"volume": "510",
"issue": "1",
"pages": "110-130"
},
{
"id": "authors:5d9pr-da453",
"collection": "authors",
"collection_id": "5d9pr-da453",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210323-124505549",
"type": "article",
"title": "Why do black holes trace bulges (& central surface densities), instead of galaxies as a whole?",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wellons",
"given_name": "Sarah",
"orcid": "0000-0002-3977-2724",
"clpid": "Wellons-Sarah"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-Michael-Y"
}
],
"abstract": "Previous studies of fueling black holes in galactic nuclei have argued (on scales \u223c0.01\u22121000pc) accretion is dynamical with inflow rates M\u02d9\u223c\u03b7M_(gas)/t_(dyn) in terms of gas mass M_(gas), dynamical time t_(dyn), and some \u03b7. But these models generally neglected expulsion of gas by stellar feedback, or considered extremely high densities where expulsion is inefficient. Studies of star formation, however, have shown on sub-kpc scales the expulsion efficiency f_(wind) = M_(ejected)/M_(total) scales with the gravitational acceleration as (1\u2212f_(wind))/f_(wind)\u223ca\u00af_(grav)/\u27e8p\u02d9/m\u2217\u27e9\u223c\u03a3_(eff)/\u03a3_(crit) where a\u00af_(grav) \u2261 GM_(tot)(",
"doi": "10.1093/mnras/stab3458",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-02",
"series_number": "1",
"volume": "510",
"issue": "1",
"pages": "630-638"
},
{
"id": "authors:3qqcb-b7g08",
"collection": "authors",
"collection_id": "3qqcb-b7g08",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-619586000",
"type": "article",
"title": "Gas infall and radial transport in cosmological simulations of milky way-mass discs",
"author": [
{
"family_name": "Trapp",
"given_name": "Cameron W.",
"orcid": "0000-0001-7813-0268",
"clpid": "Trapp-Cameron-W"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Chan",
"given_name": "Tsang Keung",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Escala",
"given_name": "Ivanna",
"orcid": "0000-0002-9933-9551",
"clpid": "Escala-Ivanna"
},
{
"family_name": "Hummels",
"given_name": "Cameron",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron-B"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-Norman-W"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
}
],
"abstract": "Observations indicate that a continuous supply of gas is needed to maintain observed star formation rates in large, discy galaxies. To fuel star formation, gas must reach the inner regions of such galaxies. Despite its crucial importance for galaxy evolution, how and where gas joins galaxies is poorly constrained observationally and rarely explored in fully cosmological simulations. To investigate gas accretion in the vicinity of galaxies at low redshift, we analyse the FIRE-2 cosmological zoom-in simulations for 4 Milky Way mass galaxies (M_(halo) \u223c 10\u00b9\u00b2 M_\u2299), focusing on simulations with cosmic ray physics. We find that at z \u223c 0, gas approaches the disc with angular momentum similar to the gaseous disc edge and low radial velocities, piling-up near the edge and settling into full rotational support. Accreting gas moves predominately parallel to the disc and joins largely in the outskirts. Immediately prior to joining the disc, trajectories briefly become more vertical on average. Within the disc, gas motion is complex, being dominated by spiral arm induced oscillations and feedback. However, time and azimuthal averages show slow net radial infall with transport speeds of 1\u20133\u00a0km\u00a0s\u207b\u00b9 and net mass fluxes through the disc of \u223cM_\u2299 yr\u207b\u00b9, comparable to the galaxies' star formation rates and decreasing towards galactic centre as gas is sunk into star formation. These rates are slightly higher in simulations without cosmic rays (1\u20137\u00a0km\u00a0s\u22121, \u223c4\u20135\u00a0M_\u2299 yr\u207b\u00b9). We find overall consistency of our results with observational constraints and discuss prospects of future observations of gas flows in and around galaxies.",
"doi": "10.1093/mnras/stab3251",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-01",
"series_number": "3",
"volume": "509",
"issue": "3",
"pages": "4149-4170"
},
{
"id": "authors:k5er1-1xw10",
"collection": "authors",
"collection_id": "k5er1-1xw10",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210323-112520656",
"type": "article",
"title": "A consistent reduced-speed-of-light formulation of cosmic ray transport valid in weak- and strong-scattering regimes",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-Jonathan"
},
{
"family_name": "Butsky",
"given_name": "Iryna S.",
"orcid": "0000-0003-1257-5007",
"clpid": "Butsky-Iryna-S"
}
],
"abstract": "We derive a consistent set of moment equations for cosmic ray (CR)-magnetohydrodynamics, assuming a gyrotropic distribution function (DF). Unlike previous efforts, we derive a closure, akin to the M1 closure in radiation hydrodynamics (RHD), that is valid in both the nearly isotropic DF and/or strong-scattering regimes, and the arbitrarily anisotropic DF or free-streaming regimes, as well as allowing for anisotropic scattering and transport/magnetic field structure. We present the appropriate two-moment closure and equations for various choices of evolved variables, including the CR phase space DF f, number density n, total energy e, kinetic energy \u03f5, and their fluxes or higher moments, and the appropriate coupling terms to the gas. We show that this naturally includes and generalizes a variety of terms including convection/fluid motion, anisotropic CR pressure, streaming, diffusion, gyro-resonant/streaming losses, and re-acceleration. We discuss how this extends previous treatments of CR transport including diffusion and moment methods and popular forms of the Fokker\u2013Planck equation, as well as how this differs from the analogous M1-RHD equations. We also present two different methods for incorporating a reduced speed of light (RSOL) to reduce time-step limitations: In both, we carefully address where the RSOL (versus true c) must appear for the correct behaviour to be recovered in all interesting limits, and show how current implementations of CRs with an RSOL neglect some additional terms.",
"doi": "10.1093/mnras/stab2635",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-01",
"series_number": "3",
"volume": "509",
"issue": "3",
"pages": "3779-3797"
},
{
"id": "authors:awnty-wcd94",
"collection": "authors",
"collection_id": "awnty-wcd94",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211215-622148000",
"type": "article",
"title": "Characterizing mass, momentum, energy, and metal outflow rates of multiphase galactic winds in the FIRE-2 cosmological simulations",
"author": [
{
"family_name": "Pandya",
"given_name": "Viraj",
"orcid": "0000-0002-2499-9205",
"clpid": "Pandya-Viraj"
},
{
"family_name": "Fielding",
"given_name": "Drummond B.",
"orcid": "0000-0003-3806-8548",
"clpid": "Fielding-Drummond-B"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Somerville",
"given_name": "Rachel S.",
"orcid": "0000-0003-2835-8533",
"clpid": "Somerville-Rachel-S"
},
{
"family_name": "Bryan",
"given_name": "Greg L.",
"orcid": "0000-0003-2630-9228",
"clpid": "Bryan-Greg-L"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565",
"clpid": "Stern-Jonathan"
},
{
"family_name": "Kim",
"given_name": "Chang-Goo",
"orcid": "0000-0003-2896-3725",
"clpid": "Kim-Chang-Goo"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Forbes",
"given_name": "John C.",
"orcid": "0000-0002-1975-4449",
"clpid": "Forbes-John-C"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-Norman-W"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
}
],
"abstract": "We characterize mass, momentum, energy, and metal outflow rates of multiphase galactic winds in a suite of FIRE-2 cosmological 'zoom-in' simulations from the Feedback in Realistic Environments (FIRE) project. We analyse simulations of low-mass dwarfs, intermediate-mass dwarfs, Milky Way-mass haloes, and high-redshift massive haloes. Consistent with previous work, we find that dwarfs eject about 100\u00a0times more gas from their interstellar medium (ISM) than they form in stars, while this mass 'loading factor' drops below one in massive galaxies. Most of the mass is carried by the hot phase (>10\u2075 K) in massive haloes and the warm phase (10\u00b3\u221210\u2075 K) in dwarfs; cold outflows (<10\u00b3 K) are negligible except in high-redshift dwarfs. Energy, momentum, and metal loading factors from the ISM are of order unity in dwarfs and significantly lower in more massive haloes. Hot outflows have 2\u22125\u00a0\u00d7 higher specific energy than needed to escape from the gravitational potential of dwarf haloes; indeed, in dwarfs, the mass, momentum, and metal outflow rates increase with radius whereas energy is roughly conserved, indicating swept up halo gas. Burst-averaged mass loading factors tend to be larger during more powerful star formation episodes and when the inner halo is not virialized, but we see effectively no trend with the dense ISM gas fraction. We discuss how our results can guide future controlled numerical experiments that aim to elucidate the key parameters governing galactic winds and the resulting associated preventative feedback.",
"doi": "10.1093/mnras/stab2714",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-12",
"series_number": "2",
"volume": "508",
"issue": "2",
"pages": "2979-3008"
},
{
"id": "authors:vc585-0q465",
"collection": "authors",
"collection_id": "vc585-0q465",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210309-082003361",
"type": "article",
"title": "Seeds don't sink: even massive black hole 'seeds' cannot migrate to galaxy centres efficiently",
"author": [
{
"family_name": "Ma",
"given_name": "Linhao",
"orcid": "0000-0001-6117-5750",
"clpid": "Ma-Linhao"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Kelley",
"given_name": "Luke Zoltan",
"orcid": "0000-0002-6625-6450",
"clpid": "Kelley-Luke-Zoltan"
}
],
"abstract": "Possible formation scenarios of supermassive black holes (BHs) in the early universe include rapid growth from less massive seed BHs via super-Eddington accretion or runaway mergers, yet both of these scenarios would require seed BHs to efficiently sink to and be trapped in the Galactic Centre via dynamical friction. This may not be true for their complicated dynamics in clumpy high-z galaxies. In this work, we study this 'sinking problem' with state-of-the-art high-resolution cosmological simulations, combined with both direct N-body integration of seed BH trajectories and post-processing of randomly generated test particles with a newly developed dynamical friction estimator. We find that seed BHs less massive than 10\u2078M\u2299 (i.e. all but the already-supermassive seeds) cannot efficiently sink in typical high-z galaxies. We also discuss two possible solutions: dramatically increasing the number of seeds such that one seed can end up trapped in the Galactic Centre by chance, or seed BHs being embedded in dense structures (e.g. star clusters) with effective masses above the mass threshold. We discuss the limitations of both solutions.",
"doi": "10.1093/mnras/stab2713",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-12",
"series_number": "2",
"volume": "508",
"issue": "2",
"pages": "1973-1985"
},
{
"id": "authors:n40ns-ff116",
"collection": "authors",
"collection_id": "n40ns-ff116",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211026-152808911",
"type": "article",
"title": "Progenitor-mass-dependent yields amplify intrinsic scatter in dwarf-galaxy elemental abundance ratios",
"author": [
{
"family_name": "Muley",
"given_name": "Dhruv A.",
"orcid": "0000-0001-6394-3215",
"clpid": "Muley-Dhruv-A"
},
{
"family_name": "Wheeler",
"given_name": "Coral R.",
"clpid": "Wheeler-Coral-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Emerick",
"given_name": "Andrew",
"orcid": "0000-0003-2807-328X",
"clpid": "Emerick-Andrew"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
}
],
"abstract": "We explore the effect of including progenitor mass- and metallicity-dependent yields, supernova rates and energetics on variations in elemental abundance ratios (particularly [\u03b1/Fe]) in dwarf galaxies. To understand how the scatter and overall trends in [\u03b1/Fe] are affected by including variable metal yields from a discretely sampled initial mass function, we run FIRE simulations of a dwarf galaxy (M\u22c6(z = 0)\u223c10\u2076M\u2299) using nucleosynthetic yields from the NuGrid data base that depend on the stellar progenitor mass and metallicity. While NuGrid exhibits lower aggregate \u03b1-element production than default FIRE yields, we find that its explicit mass dependence, even when including turbulent metal diffusion, substantially widens the intrinsic scatter in the simulated [Fe/H]-[\u03b1/Fe] \u2013 a phenomenon visible in some observations of dwarf galaxies.",
"doi": "10.1093/mnras/stab2572",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-11",
"series_number": "1",
"volume": "508",
"issue": "1",
"pages": "508-515"
},
{
"id": "authors:temyq-67y16",
"collection": "authors",
"collection_id": "temyq-67y16",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211104-211055622",
"type": "article",
"title": "Neutral CGM as damped Ly\u2009\u03b1 absorbers at high redshift",
"author": [
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565",
"clpid": "Stern-Jonathan"
},
{
"family_name": "Sternberg",
"given_name": "Amiel",
"orcid": "0000-0001-5065-9530",
"clpid": "Sternberg-Amiel"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Fielding",
"given_name": "Drummond",
"orcid": "0000-0003-3806-8548",
"clpid": "Fielding-Drummond-B"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Recent searches for the hosts of z \u223c 4 damped Ly\u2009\u03b1 absorbers (DLAs) have detected bright galaxies at distances of tens of kpc from the DLA. Using the FIRE-2 cosmological zoom simulations, we argue that these relatively large distances are due to a predominantly cool and neutral inner circumgalactic medium (CGM) surrounding high-redshift galaxies. The inner CGM is cool because of the short cooling time of hot gas in \u227210\u00b9\u00b2 M_\u2299 haloes, which implies that accretion and feedback energy are radiated quickly, while it is neutral due to high volume densities and column densities at high redshift that shield cool gas from photoionization. Our analysis predicts large DLA covering factors (\u2060\u227350 per cent) out to impact parameters \u223c0.3[(1 + z)/5]^(3/2) R_(vir) from the central galaxies at z \u2273 1, equivalent to a proper distance of \u223c21 M^(1/3)\u2081\u2082((1+z)/5)^(1/2) kpc (R_(vir) and M\u2081\u2082 are the halo virial radius and mass in units of 10\u00b9\u00b2 M_\u2299\u2060, respectively). This implies that DLA covering factors at z \u223c 4 may be comparable to unity out to a distance \u223c10 times larger than stellar half-mass radii. A predominantly neutral inner CGM in the early universe suggests that its mass and metallicity can be directly constrained by absorption surveys, without resorting to the large ionization corrections as required for ionized CGM.",
"doi": "10.1093/mnras/stab2240",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-10",
"series_number": "2",
"volume": "507",
"issue": "2",
"pages": "2869-2884"
},
{
"id": "authors:3t8a8-gsa79",
"collection": "authors",
"collection_id": "3t8a8-gsa79",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211020-174301603",
"type": "article",
"title": "Which AGN jets quench star formation in massive galaxies?",
"author": [
{
"family_name": "Su",
"given_name": "Kung-Yi",
"orcid": "0000-0003-1598-0083",
"clpid": "Su-Kung-Yi"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Bryan",
"given_name": "Greg L.",
"orcid": "0000-0003-2630-9228",
"clpid": "Bryan-Greg-L"
},
{
"family_name": "Somerville",
"given_name": "Rachel S.",
"orcid": "0000-0003-2835-8533",
"clpid": "Somerville-Rachel-S"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Wellons",
"given_name": "Sarah",
"orcid": "0000-0002-3977-2724",
"clpid": "Wellons-Sarah"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565",
"clpid": "Stern-Jonathan"
},
{
"family_name": "Terrazas",
"given_name": "Bryan A.",
"orcid": "0000-0001-5529-7305",
"clpid": "Terrazas-Bryan-A"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-Matthew-E"
},
{
"family_name": "Hummels",
"given_name": "Cameron",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron-B"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
}
],
"abstract": "Without additional heating, radiative cooling of the halo gas of massive galaxies (Milky Way-mass and above) produces cold gas or stars exceeding that observed. Heating from active galactic nucleus (AGN) jets is likely required, but the jet properties remain unclear. This is particularly challenging for galaxy simulations, where the resolution is orders-of-magnitude insufficient to resolve jet formation and evolution. On such scales, the uncertain parameters include the jet energy form [kinetic, thermal, cosmic ray (CR)]; energy, momentum, and mass flux; magnetic fields; opening angle; precession; and duty cycle. We investigate these parameters in a 10\u00b9\u2074M\u2299 halo using high-resolution non-cosmological magnetohydrodynamic simulations with the FIRE-2 (Feedback In Realistic Environments) stellar feedback model, conduction, and viscosity. We explore which scenarios qualitatively meet observational constraints on the halo gas and show that CR-dominated jets most efficiently quench the galaxy by providing CR pressure support and modifying the thermal instability. Mildly relativistic (\u223cMeV or \u223c10\u00b9\u2070K) thermal plasma jets work but require \u223c10 times larger energy input. For fixed energy flux, jets with higher specific energy (longer cooling times) quench more effectively. For this halo mass, kinetic jets are inefficient at quenching unless they have wide opening or precession angles. Magnetic fields also matter less except when the magnetic energy flux reaches \u2273 10\u2074\u2074 erg\u2009s\u207b\u00b9 in a kinetic jet model, which significantly widens the jet cocoon. The criteria for a successful jet model are an optimal energy flux and a sufficiently wide jet cocoon with a long enough cooling time at the cooling radius.",
"doi": "10.1093/mnras/stab2021",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-10",
"series_number": "1",
"volume": "507",
"issue": "1",
"pages": "175-204"
},
{
"id": "authors:r1973-a2n73",
"collection": "authors",
"collection_id": "r1973-a2n73",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211020-212403723",
"type": "article",
"title": "The central densities of Milky Way-mass galaxies in cold and self-interacting dark matter models",
"author": [
{
"family_name": "Sameie",
"given_name": "Omid",
"orcid": "0000-0003-4394-6085",
"clpid": "Sameie-Omid"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Sanderson",
"given_name": "Robyn",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-Robyn-E"
},
{
"family_name": "Vargya",
"given_name": "Drona",
"clpid": "Vargya-Drona"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Graus",
"given_name": "Andrew",
"clpid": "Graus-Andrew-S"
},
{
"family_name": "Robles",
"given_name": "Victor H.",
"orcid": "0000-0002-9497-9963",
"clpid": "Robles-Victor-H"
}
],
"abstract": "We present a suite of baryonic cosmological zoom-in simulations of self-interacting dark matter (SIDM) haloes within the 'Feedback In Realistic Environment' (FIRE) project. The three simulated haloes have virial masses of \u223c10\u00b9\u00b2M\u2299 at z = 0, and we study velocity-independent self-interaction cross sections of 1 and 10 cm\u00b2g\u207b\u00b9\u2060. We study star formation rates and the shape of dark matter density profiles of the parent haloes in both cold dark matter (CDM) and SIDM models. Galaxies formed in the SIDM haloes have higher star formation rates at z \u2264 1, resulting in more massive galaxies compared to the CDM simulations. While both CDM and SIDM simulations show diverse shape of the dark matter density profiles, the SIDM haloes can reach higher and more steep central densities within few kpcs compared to the CDM haloes. We identify a correlation between the build-up of the stars within the half-mass radii of the galaxies and the growth in the central dark matter densities. The thermalization process in the SIDM haloes is enhanced in the presence of a dense stellar component. Hence, SIDM haloes with highly concentrated baryonic profiles are predicted to have higher central dark matter densities than the CDM haloes. Overall, the SIDM haloes are more responsive to the presence of a massive baryonic distribution than their CDM counterparts.",
"doi": "10.1093/mnras/stab2173",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-10",
"series_number": "1",
"volume": "507",
"issue": "1",
"pages": "720-729"
},
{
"id": "authors:ej3hx-j7v73",
"collection": "authors",
"collection_id": "ej3hx-j7v73",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210428-103121850",
"type": "article",
"title": "Dissipative dark matter on FIRE \u2013 I. Structural and kinematic properties of dwarf galaxies",
"author": [
{
"family_name": "Shen",
"given_name": "Xuejian",
"orcid": "0000-0002-6196-823X",
"clpid": "Shen-Xuejian"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Necib",
"given_name": "Lina",
"orcid": "0000-0003-2806-1414",
"clpid": "Necib-Lina"
},
{
"family_name": "Jiang",
"given_name": "Fangzhou",
"orcid": "0000-0001-6115-0633",
"clpid": "Jiang-Fangzhou"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
}
],
"abstract": "We present the first set of cosmological baryonic zoom-in simulations of galaxies including dissipative self-interacting dark matter (dSIDM). These simulations utilize the Feedback In Realistic Environments galaxy formation physics, but allow the dark matter to have dissipative self-interactions analogous to standard model forces, parametrized by the self-interaction cross-section per unit mass, (\u03c3/m), and the dimensionless degree of dissipation, 0 < f_(diss) < 1. We survey this parameter space, including constant and velocity-dependent cross-sections, and focus on structural and kinematic properties of dwarf galaxies with M_(halo)\u223c10\u00b9\u2070\u207b\u00b9\u00b9 M\u2299 and M\u2217\u223c10\u2075\u207b\u2078 M\u2299. Central density profiles (parametrized as \u03c1 \u221d r\u03b1) of simulated dwarfs become cuspy when (\u03c3/m)_(eff) \u2273 0.1cm\u00b2g\u207b\u00b9 (and f_(diss) = 0.5 as fiducial). The power-law slopes asymptote to \u03b1 \u2248 \u22121.5 in low-mass dwarfs independent of cross-section, which arises from a dark matter 'cooling flow'. Through comparisons with dark matter only simulations, we find the profile in this regime is insensitive to the inclusion of baryons. However, when (\u03c3/m)_(eff) \u226a 0.1cm\u00b2g\u207b\u00b9\u2060, baryonic effects can produce cored density profiles comparable to non-dissipative cold dark matter (CDM) runs but at smaller radii. Simulated galaxies with (\u03c3/m) \u2273 10cm\u00b2g\u207b\u00b9 and the fiducial f_(diss) develop significant coherent rotation of dark matter, accompanied by halo deformation, but this is unlike the well-defined thin 'dark discs' often attributed to baryon-like dSIDM. The density profiles in this high cross-section model exhibit lower normalizations given the onset of halo deformation. For our surveyed dSIDM parameters, halo masses and galaxy stellar masses do not show appreciable difference from CDM, but dark matter kinematics and halo concentrations/shapes can differ.",
"doi": "10.1093/mnras/stab2042",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-09",
"series_number": "3",
"volume": "506",
"issue": "3",
"pages": "4421-4445"
},
{
"id": "authors:svdak-rpj07",
"collection": "authors",
"collection_id": "svdak-rpj07",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211026-215215582",
"type": "article",
"title": "STARFORGE: Toward a comprehensive numerical model of star cluster formation and feedback",
"author": [
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-Michael-Y"
},
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D\u00e1vid"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Offner",
"given_name": "Stella S. R.",
"orcid": "0000-0003-1252-9916",
"clpid": "Offner-Stella-S-R"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
}
],
"abstract": "We present STARFORGE (STAR FORmation in Gaseous Environments): a new numerical framework for 3D radiation magnetohydrodynamic (MHD) simulations of star formation that simultaneously follow the formation, accretion, evolution, and dynamics of individual stars in massive giant molecular clouds (GMCs), while accounting for stellar feedback, including jets, radiative heating and momentum, stellar winds, and supernovae. We use the GIZMO code with the MFM mesh-free Lagrangian MHD method, augmented with new algorithms for gravity, time-stepping, sink particle formation and accretion, stellar dynamics, and feedback coupling. We survey a wide range of numerical parameters/prescriptions for sink formation and accretion and find very small variations in star formation history and the IMF (except for intentionally unphysical variations). Modules for mass-injecting feedback (winds, SNe, and jets) inject new gas elements on the fly, eliminating the lack of resolution in diffuse feedback cavities otherwise inherent in Lagrangian methods. The treatment of radiation uses GIZMO's radiative transfer solver to track five frequency bands (IR, optical, NUV, FUV, ionizing), coupling direct stellar emission and dust emission with gas heating and radiation pressure terms. We demonstrate accurate solutions for SNe, winds, and radiation in problems with known similarity solutions, and show that our jet module is robust to resolution and numerical details, and agrees well with previous AMR simulations. STARFORGE can scale up to massive (>10\u2075\u2009M\u2299) GMCs on current supercomputers while predicting the stellar (\u22730.1\u2009M\u2299) range of the IMF, permitting simulations of both high- and low-mass cluster formation in a wide range of conditions.",
"doi": "10.1093/mnras/stab1347",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-09",
"series_number": "2",
"volume": "506",
"issue": "2",
"pages": "2199-2231"
},
{
"id": "authors:s30xc-2g444",
"collection": "authors",
"collection_id": "s30xc-2g444",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211001-193558774",
"type": "article",
"title": "A model for the formation of stellar associations and clusters from giant molecular clouds",
"author": [
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-Michael-Y"
},
{
"family_name": "Diederik\u00a0Kruijssen",
"given_name": "J. M.",
"orcid": "0000-0002-8804-0212",
"clpid": "Diederik-Kruijssen-J"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
}
],
"abstract": "We present a large suite of magnetohydrodynamic simulations of turbulent, star-forming giant molecular clouds (GMCs) with stellar feedback, extending previous work by simulating 10 different random realizations for each point in the parameter space of cloud mass and size. It is found that once the clouds disperse due to stellar feedback, both self-gravitating star clusters and unbound stars generally remain, which arise from the same underlying continuum of substructured stellar density, i.e. the hierarchical cluster formation scenario. The fraction of stars that are born within gravitationally bound star clusters is related to the overall cloud star formation efficiency set by stellar feedback, but has significant scatter due to stochastic variations in the small-scale details of the star-forming gas flow. We use our numerical results to calibrate a model for mapping the bulk properties (mass, size, and metallicity) of self-gravitating GMCs on to the star cluster populations they form, expressed statistically in terms of cloud-level distributions. Synthesizing cluster catalogues from an observed GMC catalogue in M83, we find that this model predicts initial star cluster masses and sizes that are in good agreement with observations, using only standard IMF and stellar evolution models as inputs for feedback. Within our model, the ratio of the strength of gravity to stellar feedback is the key parameter setting the masses of star clusters, and of the various feedback channels direct stellar radiation (photon momentum and photoionization) is the most important on GMC scales.",
"doi": "10.1093/mnras/stab1894",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-09",
"series_number": "3",
"volume": "506",
"issue": "3",
"pages": "3239-3258"
},
{
"id": "authors:q5xjf-5xf02",
"collection": "authors",
"collection_id": "q5xjf-5xf02",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210914-225356647",
"type": "article",
"title": "Cosmological Simulations of Quasar Fueling to Subparsec Scales Using Lagrangian Hyper-refinement",
"author": [
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Somerville",
"given_name": "Rachel S.",
"orcid": "0000-0003-2835-8533",
"clpid": "Somerville-Rachel-S"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Bryan",
"given_name": "Greg L.",
"orcid": "0000-0003-2630-9228",
"clpid": "Bryan-Greg-L"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-Lars"
},
{
"family_name": "Stone",
"given_name": "James M.",
"orcid": "0000-0001-5603-1832",
"clpid": "Stone-James-M"
}
],
"abstract": "We present cosmological hydrodynamic simulations of a quasar-mass halo (M_(halo) \u2248 10^(12.5) M_\u2299 at z = 2) that for the first time resolve gas transport down to the inner 0.1 pc surrounding the central massive black hole. We model a multiphase interstellar medium including stellar feedback by supernovae, stellar winds, and radiation, and a hyper-Lagrangian refinement technique increasing the resolution dynamically approaching the black hole. We do not include black hole feedback. We show that the subpc inflow rate (1) can reach \u223c6 M_\u2299 yr\u207b\u00b9 roughly in steady state during the epoch of peak nuclear gas density (z \u223c 2), sufficient to power a luminous quasar, (2) is highly time variable in the pre-quasar phase, spanning 0.001\u201310 M_\u2299 yr\u207b\u00b9 on Myr timescales, and (3) is limited to short (\u223c2 Myr) active phases (0.01\u20130.1 M_\u2299 yr\u207b\u00b9) followed by longer periods of inactivity at lower nuclear gas density and late times (z \u223c 1), owing to the formation of a hot central cavity. Inflowing gas is primarily cool, rotational support dominates over turbulence and thermal pressure, and star formation can consume as much gas as provided by inflows across 1 pc\u201310 kpc. Gravitational torques from multiscale stellar non-axisymmetries dominate angular momentum transport over gas self-torquing and pressure gradients, with accretion weakly dependent on black hole mass. Subpc inflow rates correlate with nuclear (but decouple from global) star formation and can exceed the Eddington rate by \u00d710. The black hole can move \u223c10 pc from the galaxy center on \u223c0.1 Myr. Accreting gas forms pc-scale, rotationally supported, obscuring structures often misaligned with the galaxy-scale disk. These simulations open a new avenue to investigate black hole\u2013galaxy coevolution.",
"doi": "10.3847/1538-4357/ac09e8",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2021-08-20",
"series_number": "2",
"volume": "917",
"issue": "2",
"pages": "Art. No. 53"
},
{
"id": "authors:475fg-vzn23",
"collection": "authors",
"collection_id": "475fg-vzn23",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200922-124141959",
"type": "article",
"title": "The mass budget for intermediate-mass black holes in dense star clusters",
"author": [
{
"family_name": "Shi",
"given_name": "Yanlong",
"orcid": "0000-0002-0087-3237",
"clpid": "Shi-Yanlong"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-Michael-Y"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Intermediate-mass black holes (IMBHs) could form via runaway merging of massive stars in a young massive star cluster (YMC). We combine a suite of numerical simulations of YMC formation with a semi-analytic model for dynamical friction and merging of massive stars and evolution of a central quasi-star, to predict how final quasi-star and relic IMBH masses scale with cluster properties (and compare with observations). The simulations argue that inner YMC density profiles at formation are steep (approaching isothermal), producing some efficient merging even in clusters with relatively low effective densities, unlike models that assume flat central profiles resembling those of globular clusters after central relaxation. Our results can be approximated by simple analytic scalings, with M_(IMBH) \u221d v^(3/2)_(cl) where v\u00b2_(cl) = GM_(cl)/r_h is the circular velocity in terms of initial cluster mass Mcl and half-mass radius rh. While this suggests IMBH formation is possible even in typical clusters, we show that predicted IMBH masses for these systems are small, \u223c100\u22121000 M_\u2299 or \u223c0.0003 M_(cl) \u2060, below even the most conservative observational upper limits in all known cases. The IMBH mass could reach \u2273 10\u2074 M\u2299 in the centres nuclear star clusters, ultra-compact dwarfs, or compact ellipticals, but in all these cases the prediction remains far below the present observed supermassive BH masses in these systems.",
"doi": "10.1093/mnras/stab1470",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-08",
"series_number": "2",
"volume": "505",
"issue": "2",
"pages": "2753-2763"
},
{
"id": "authors:cek6z-7q744",
"collection": "authors",
"collection_id": "cek6z-7q744",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210106-102315985",
"type": "article",
"title": "Virial shocks are suppressed in cosmic ray-dominated galaxy haloes",
"author": [
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565",
"clpid": "Stern-Jonathan"
},
{
"family_name": "Hummels",
"given_name": "Cameron B.",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron-B"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
}
],
"abstract": "We study the impact of cosmic rays (CRs) on the structure of virial shocks, using a large suite of high-resolution cosmological FIRE-2 simulations accounting for CR injection by supernovae. In Milky Way-mass, low-redshift (z \u2272 1\u22122) haloes, which are expected to form 'hot haloes' with slowly cooling gas in quasi-hydrostatic equilibrium (with a stable virial shock), our simulations without CRs do exhibit clear virial shocks. The cooler phase condensing out from inflows becomes pressure confined to overdense clumps, embedded in low-density, volume-filling hot gas with volume-weighted cooling time longer than inflow time. The gas thus transitions sharply from cool free-falling inflow, to hot and thermal-pressure supported at approximately the virial radius (\u2248R_(vir)), and the shock is quasi-spherical. With CRs, we previously argued that haloes in this particular mass and redshift range build up CR-pressure-dominated gaseous haloes. Here, we show that when CR pressure dominates over thermal pressure, there is no significant virial shock. Instead, inflowing gas is gradually decelerated by the CR pressure gradient and the gas is relatively subsonic out to and even beyond R_(vir). Rapid cooling also maintains subvirial temperatures in the inflowing gas within \u223cR_(vir).",
"doi": "10.1093/mnras/stab1264",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-07",
"series_number": "1",
"volume": "505",
"issue": "1",
"pages": "259-273"
},
{
"id": "authors:reagp-46210",
"collection": "authors",
"collection_id": "reagp-46210",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210302-122414919",
"type": "article",
"title": "First light from tidal disruption events",
"author": [
{
"family_name": "Bonnerot",
"given_name": "Cl\u00e9ment",
"orcid": "0000-0001-9970-2843",
"clpid": "Bonnerot-Cl\u00e9ment"
},
{
"family_name": "Lu",
"given_name": "Wenbin",
"orcid": "0000-0002-1568-7461",
"clpid": "Lu-Wenbin"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "When a star comes too close to a supermassive black hole, it gets torn apart by strong tidal forces in a tidal disruption event, or TDE. Half of the elongated stream of debris comes back to the stellar pericentre where relativistic apsidal precession induces a self-crossing shock. As a result, the gas gets launched into an outflow that can experience additional interactions, leading to the formation of an accretion disc. We carry out the first radiation\u2013hydrodynamics simulations of this process, making use of the same injection procedure to treat the self-crossing shock as in our previous adiabatic study. Two sets of realistic parameters of the problem are considered that correspond to different strengths of this initial interaction. In both cases, we find that the injected matter has its trajectories promptly circularized by secondary shocks taking place near the black hole. However, the generated internal energy efficiently diffuses away in the form of radiation, which results in a thin vertical profile of the formed disc. The diffusing photons promptly irradiate the surrounding debris until they emerge with a bolometric luminosity of L \u2248 10\u2074\u2074 erg s\u207b\u00b9. Towards the self-crossing shock, diffusion is, however, slowed that results in a shallower luminosity increase, with a potentially significant component in the optical band. Matter launched to large distances continuously gains energy through radiation pressure, which can cause a significant fraction to become unbound. This work provides direct insight into the origin of the early emission from TDEs, which is accessed by a rapidly increasing number of observations.",
"doi": "10.1093/mnras/stab398",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-07",
"series_number": "4",
"volume": "504",
"issue": "4",
"pages": "4885-4905"
},
{
"id": "authors:wz6cb-8rc66",
"collection": "authors",
"collection_id": "wz6cb-8rc66",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210803-200634030",
"type": "article",
"title": "The bursty origin of the Milky Way thick disc",
"author": [
{
"family_name": "Yu",
"given_name": "Sijie",
"orcid": "0000-0002-1019-0341",
"clpid": "Yu-Sijie"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Klein",
"given_name": "Courtney",
"orcid": "0000-0002-2762-4046",
"clpid": "Klein-Courtney"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565",
"clpid": "Stern-Jonathan"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232",
"clpid": "Moreno-Jorge"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Gurvich",
"given_name": "Alexander B.",
"orcid": "0000-0002-6145-3674",
"clpid": "Gurvich-Alexander-B"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
}
],
"abstract": "We investigate thin and thick stellar disc formation in Milky Way-mass galaxies using 12 FIRE-2 cosmological zoom-in simulations. All simulated galaxies experience an early period of bursty star formation that transitions to a late-time steady phase of near-constant star formation. Stars formed during the late-time steady phase have more circular orbits and thin-disc-like morphology at z = 0, while stars born during the bursty phase have more radial orbits and thick-disc structure. The median age of thick-disc stars at z = 0 correlates strongly with this transition time. We also find that galaxies with an earlier transition from bursty to steady star formation have a higher thin-disc fractions at z = 0. Three of our systems have minor mergers with Large Magellanic Cloud-size satellites during the thin-disc phase. These mergers trigger short starbursts but do not destroy the thin disc nor alter broad trends between the star formation transition time and thin/thick-disc properties. If our simulations are representative of the Universe, then stellar archaeological studies of the Milky Way (or M31) provide a window into past star formation modes in the Galaxy. Current age estimates of the Galactic thick disc would suggest that the Milky Way transitioned from bursty to steady phase \u223c6.5 Gyr ago; prior to that time the Milky Way likely lacked a recognizable thin disc.",
"doi": "10.1093/mnras/stab1339",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-07",
"series_number": "1",
"volume": "505",
"issue": "1",
"pages": "889-902"
},
{
"id": "authors:93ded-2a215",
"collection": "authors",
"collection_id": "93ded-2a215",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210408-124720174",
"type": "article",
"title": "SMBH seeds from dissipative dark matter",
"author": [
{
"family_name": "Xiao",
"given_name": "Huangyu",
"orcid": "0000-0003-2485-5700",
"clpid": "Xiao-Huangyu"
},
{
"family_name": "Shen",
"given_name": "Xuejian",
"orcid": "0000-0002-6196-823X",
"clpid": "Shen-Xuejian"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Zurek",
"given_name": "Kathryn M.",
"orcid": "0000-0002-2629-337X",
"clpid": "Zurek-K-M"
}
],
"abstract": "The existence of supermassive black holes (SMBHs) with masses greater than ~ 10\u2079M\u2609 at high redshift (z \u2273 7) is difficult to accommodate in standard astrophysical scenarios. We study the possibility that (nearly) totally dissipative self-interacting dark matter (tdSIDM)\u2013in rare, high density dark matter fluctuations in the early Universe \u2014 produces SMBH seeds through catastrophic collapse. We use a semi-analytic model, tested and calibrated by a series of N-body simulations of isolated dark matter halos, to compute the collapse criteria and timescale of tdSIDM halos, where dark matter loses nearly all of its kinetic energy in a single collision in the center-of-momentum frame. Applying this model to halo merger trees, we empirically assign SMBH seeds to halos and trace the formation and evolution history of SMBHs. We make predictions for the quasar luminosity function, the M_(BH)-\u03c3_v* relation, and cosmic SMBH mass density at high redshift and compare them to observations. We find that a dissipative dark matter interaction cross-section of \u03c3/m ~ 0.05 cm\u00b2/g is sufficient to produce the SMBHs observed in the early Universe while remaining consistent with ordinary SMBHs in the late Universe.",
"doi": "10.1088/1475-7516/2021/07/039",
"issn": "1475-7516",
"publisher": "IOP",
"publication": "Journal of Cosmology and Astroparticle Physics",
"publication_date": "2021-07",
"series_number": "7",
"volume": "2021",
"issue": "7",
"pages": "Art. No. 039"
},
{
"id": "authors:rvz7e-4hv67",
"collection": "authors",
"collection_id": "rvz7e-4hv67",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210630-162633099",
"type": "article",
"title": "Planes of satellites around Milky Way/M31-mass galaxies in the FIRE simulations and comparisons with the Local Group",
"author": [
{
"family_name": "Samuel",
"given_name": "Jenna",
"orcid": "0000-0002-8429-4100",
"clpid": "Samuel-Jenna"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Chapman",
"given_name": "Sierra",
"clpid": "Chapman-Sierra"
},
{
"family_name": "Tollerud",
"given_name": "Erik",
"orcid": "0000-0002-9599-310X",
"clpid": "Tollerud-Erik-J"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Bailin",
"given_name": "Jeremy",
"clpid": "Bailin-Jeremy"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
}
],
"abstract": "We examine the prevalence, longevity, and causes of planes of satellite dwarf galaxies, as observed in the Local Group. We use 14 Milky Way/Andromeda-(MW/M31) mass host galaxies from the Feedback In Realistic Environments-2 simulations. We select the 14 most massive satellites by stellar mass within d_(host) \u2264 300kpc of each host and correct for incompleteness from the foreground galactic disc when comparing to the MW. We find that MW-like planes as spatially thin and/or kinematically coherent as observed are uncommon, but they do exist in our simulations. Spatially thin planes occur in 1\u20132\u2009per\u2009cent of snapshots during z = 0\u22120.2, and kinematically coherent planes occur in 5\u2009per\u2009cent of snapshots. These planes are generally transient, surviving for <500\u2009Myr. However, if we select hosts with a Large Magellanic Cloud-like satellite near first pericentre, the fraction of snapshots with MW-like planes increases dramatically to 7\u201316\u2009per\u2009cent, with lifetimes of \u20090.7\u20131\u2009Gyr, likely because of group accretion of satellites. We find that M31's satellite distribution is much more common: M31's satellites lie within \u223c1\u03c3 of the simulation median for every plane metric we consider. We find no significant difference in average satellite planarity for isolated hosts versus hosts in LG-like pairs. Baryonic and dark matter-only simulations exhibit similar levels of planarity, even though baryonic subhaloes are less centrally concentrated within their host haloes. We conclude that planes of satellites are not a strong challenge to \u039bCDM cosmology.",
"doi": "10.1093/mnras/stab955",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-06",
"series_number": "1",
"volume": "504",
"issue": "1",
"pages": "1379-1397"
},
{
"id": "authors:8tbsa-fpq26",
"collection": "authors",
"collection_id": "8tbsa-fpq26",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210621-223906560",
"type": "article",
"title": "Spatially resolved star formation and fuelling in galaxy interactions",
"author": [
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232",
"clpid": "Moreno-Jorge"
},
{
"family_name": "Torrey",
"given_name": "Paul",
"orcid": "0000-0002-5653-0786",
"clpid": "Torrey-Paul"
},
{
"family_name": "Ellison",
"given_name": "Sara L.",
"orcid": "0000-0002-1768-1899",
"clpid": "Ellison-Sara-L"
},
{
"family_name": "Patton",
"given_name": "David R",
"orcid": "0000-0002-1871-4154",
"clpid": "Patton-David-R"
},
{
"family_name": "Bottrell",
"given_name": "Connor",
"orcid": "0000-0003-4758-4501",
"clpid": "Bottrell-Connor"
},
{
"family_name": "Bluck",
"given_name": "Asa F. L.",
"orcid": "0000-0001-6395-4504",
"clpid": "Bluck-Asa-F-L"
},
{
"family_name": "Hani",
"given_name": "Maan H.",
"orcid": "0000-0002-5351-2291",
"clpid": "Hani-Maan-H"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-Lars"
}
],
"abstract": "We investigate the spatial structure and evolution of star formation and the interstellar medium (ISM) in interacting galaxies. We use an extensive suite of parsec-scale galaxy-merger simulations (stellar mass ratio = 2.5:1), which employs the 'Feedback In Realistic Environments-2' model (FIRE-2). This framework resolves star formation, feedback processes, and the multiphase structure of the ISM. We focus on the galaxy-pair stages of interaction. We find that close encounters substantially augment cool (H\u2009I) and cold-dense (H\u2082) gas budgets, elevating the formation of new stars as a result. This enhancement is centrally concentrated for the secondary galaxy, and more radially extended for the primary. This behaviour is weakly dependent on orbital geometry. We also find that galaxies with elevated global star formation rate (SFR) experience intense nuclear SFR enhancement, driven by high levels of either star formation efficiency (SFE) or available cold-dense gas fuel. Galaxies with suppressed global SFR also contain a nuclear cold-dense gas reservoir, but low SFE levels diminish SFR in the central region. Concretely, in the majority of cases, SFR enhancement in the central kiloparsec is fuel-driven (55 per cent for the secondary, 71 per cent for the primary) \u2013 while central SFR suppression is efficiency-driven (91 per cent for the secondary, 97 per cent for the primary). Our numerical predictions underscore the need of substantially larger, and/or merger-dedicated, spatially resolved galaxy surveys \u2013 capable of examining vast and diverse samples of interacting systems \u2013 coupled with multiwavelength campaigns aimed to capture their internal ISM structure.",
"doi": "10.1093/mnras/staa2952",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-05",
"series_number": "3",
"volume": "503",
"issue": "3",
"pages": "3113-3133"
},
{
"id": "authors:a7z4d-dce64",
"collection": "authors",
"collection_id": "a7z4d-dce64",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210423-164858810",
"type": "article",
"title": "Virialization of the Inner CGM in the FIRE Simulations and Implications for Galaxy Disks, Star Formation, and Feedback",
"author": [
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565",
"clpid": "Stern-Jonathan"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Fielding",
"given_name": "Drummond",
"orcid": "0000-0003-3806-8548",
"clpid": "Fielding-Drummond-B"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Hafen",
"given_name": "Zachary H.",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Gurvich",
"given_name": "Alexander B.",
"orcid": "0000-0002-6145-3674",
"clpid": "Gurvich-Alexander-B"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Byrne",
"given_name": "Lindsey",
"orcid": "0000-0002-8408-1834",
"clpid": "Byrne-Lindsey"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Murray",
"given_name": "Norman",
"orcid": "0000-0002-8659-3729",
"clpid": "Murray-Norman-W"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We use the FIRE-2 cosmological simulations to study the formation of a quasi-static, virial-temperature gas phase in the circumgalactic medium (CGM) at redshifts 0 < z < 5 and how the formation of this virialized phase affects the evolution of galactic disks. We demonstrate that when the halo mass crosses ~10\u00b9\u00b2 M_\u2299, the cooling time of shocked gas in the inner CGM (~0.1R_(vir), where R_(vir) is the virial radius) exceeds the local free-fall time. The inner CGM then experiences a transition from on average subvirial temperatures (T \u00ab T_(vir)), large pressure fluctuations, and supersonic inflow/outflow velocities to virial temperatures (T ~ T_(vir)), uniform pressures, and subsonic velocities. This transition occurs when the outer CGM (~0.5R_(vir)) is already subsonic and has a temperature ~T_(vir), indicating that the longer cooling times at large radii allow the outer CGM to virialize at lower halo masses than the inner CGM. This outside-in CGM virialization scenario is in contrast with inside-out scenarios commonly envisioned based on more idealized simulations. We demonstrate that inner CGM virialization coincides with abrupt changes in the central galaxy and its stellar feedback: the galaxy settles into a stable rotating disk, star formation transitions from \"bursty\" to \"steady,\" and stellar-driven galaxy-scale outflows are suppressed. Our results thus suggest that CGM virialization is initially associated with the formation of rotation-dominated thin galactic disks, rather than with the quenching of star formation as often assumed.",
"doi": "10.3847/1538-4357/abd776",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2021-04-20",
"series_number": "2",
"volume": "911",
"issue": "2",
"pages": "Art. No. 88"
},
{
"id": "authors:wbbha-ccp78",
"collection": "authors",
"collection_id": "wbbha-ccp78",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210602-104241885",
"type": "article",
"title": "STARFORGE: the effects of protostellar outflows on the IMF",
"author": [
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D\u00e1vid"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-Michael-Y"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Offner",
"given_name": "Stella S. R.",
"orcid": "0000-0003-1252-9916",
"clpid": "Offner-Stella-S-R"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
}
],
"abstract": "The initial mass function (IMF) of stars is a key quantity affecting almost every field of astrophysics, yet it remains unclear what physical mechanisms determine it. We present the first runs of the STAR FORmation in Gaseous Environments project, using a new numerical framework to follow the formation of individual stars in giant molecular clouds (GMCs) using the GIZMO code. Our suite includes runs with increasingly complex physics, starting with isothermal ideal magnetohydrodynamics (MHD) and then adding non-isothermal thermodynamics and protostellar outflows. We show that without protostellar outflows the resulting stellar masses are an order of magnitude too high, similar to the result in the base isothermal MHD run. Outflows disrupt the accretion flow around the protostar, allowing gas to fragment and additional stars to form, thereby lowering the mean stellar mass to a value similar to that observed. The effect of jets upon global cloud evolution is most pronounced for lower mass GMCs and dense clumps, so while jets can disrupt low-mass clouds, they are unable to regulate star formation in massive GMCs, as they would turn an order unity fraction of the mass into stars before unbinding the cloud. Jets are also unable to stop the runaway accretion of massive stars, which could ultimately lead to the formation of stars with masses >500M\u2299\u2060. Although we find that the mass scale set by jets is insensitive to most cloud parameters (i.e. surface density, virial parameter), it is strongly dependent on the momentum loading of the jets (which is poorly constrained by observations) as well as the temperature of the parent cloud, which predicts slightly larger IMF variations than observed. We conclude that protostellar jets play a vital role in setting the mass scale of stars, but additional physics are necessary to reproduce the observed IMF.",
"doi": "10.1093/mnras/stab278",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-04",
"series_number": "3",
"volume": "502",
"issue": "3",
"pages": "3646-3663"
},
{
"id": "authors:k939b-gz730",
"collection": "authors",
"collection_id": "k939b-gz730",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210602-084203342",
"type": "article",
"title": "The impact of astrophysical dust grains on the confinement of cosmic rays",
"author": [
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-Jonathan"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Kempski",
"given_name": "Philipp",
"clpid": "Kempski-Philipp"
}
],
"abstract": "We argue that charged dust grains could significantly impact the confinement and transport of galactic cosmic rays. For sub-GeV to \u223c103\u2009GeV cosmic rays, small-scale parallel Alfv\u00e9n waves, which isotropize cosmic rays through gyro-resonant interactions, are also gyro-resonant with charged grains. If the dust is nearly stationary, as in the bulk of the interstellar medium, Alfv\u00e9n waves are damped by dust. This will reduce the amplitude of Alfv\u00e9n waves produced by the cosmic rays through the streaming instability, thus enhancing cosmic ray transport. In well-ionized regions, the dust damping rate is larger by a factor of \u223c10 than other mechanisms that damp parallel Alfv\u00e9n waves at the scales relevant for \u223cGeV cosmic rays, suggesting that dust could play a key role in regulating cosmic ray transport. In astrophysical situations in which the dust moves through the gas with super-Alfv\u00e9nic velocities, Alfv\u00e9n waves are rendered unstable, which could directly scatter cosmic rays. This interaction has the potential to create a strong feedback mechanism where dust, driven through the gas by radiation pressure, then strongly enhances the confinement of cosmic rays, increasing their capacity to drive outflows. This mechanism may act in the circumgalactic medium around star-forming galaxies and active galactic nuclei.",
"doi": "10.1093/mnras/stab179",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-04",
"series_number": "2",
"volume": "502",
"issue": "2",
"pages": "2630-2644"
},
{
"id": "authors:j8s4k-zz766",
"collection": "authors",
"collection_id": "j8s4k-zz766",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210602-072448048",
"type": "article",
"title": "The IRX\u2013\u03b2 relation of high-redshift galaxies",
"author": [
{
"family_name": "Liang",
"given_name": "Lichen",
"orcid": "0000-0001-9422-0095",
"clpid": "Liang-Lichen"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-Desika"
},
{
"family_name": "\u00c7atmabacak",
"given_name": "Onur",
"clpid": "\u00c7atmabacak-Onur"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "The relation between infrared excess (IRX) and UV spectral slope (\u03b2_(UV)) is an empirical probe of dust properties of galaxies. The shape, scatter, and redshift evolution of this relation are not well understood, however, leading to uncertainties in estimating the dust content and star formation rates (SFRs) of galaxies at high redshift. In this study, we explore the nature and properties of the IRX\u2013\u03b2_(UV) relation with a sample of z = 2\u20136 galaxies (\u2060M\u2217 \u2248 10\u2079\u221210\u00b9\u00b2M\u2299\u2060) extracted from high-resolution cosmological simulations (MassiveFIRE) of the Feedback in Realistic Environments (FIRE) project. The galaxies in our sample show an IRX\u2013\u03b2UV relation that is in good agreement with the observed relation in nearby galaxies. IRX is tightly coupled to the UV optical depth, and is mainly determined by the dust-to-star geometry instead of total dust mass, while \u03b2_(UV) is set both by stellar properties, UV optical depth, and the dust extinction law. Overall, much of the scatter in the IRX\u2013\u03b2_(UV) relation of our sample is found to be driven by variations of the intrinsic UV spectral slope. We further assess how the IRX\u2013\u03b2_(UV) relation depends on viewing direction, dust-to-metal ratio, birth-cloud structures, and the dust extinction law and we present a simple model that encapsulates most of the found dependencies. Consequently, we argue that the reported 'deficit' of the infrared/sub-millimetre bright objects at z \u2273 5 does not necessarily imply a non-standard dust extinction law at those epochs.",
"doi": "10.1093/mnras/stab096",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-04",
"series_number": "3",
"volume": "502",
"issue": "3",
"pages": "3210-3241"
},
{
"id": "authors:v7hv0-03303",
"collection": "authors",
"collection_id": "v7hv0-03303",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210311-091942314",
"type": "article",
"title": "The Origin and Evolution of Ly\u03b1\u00a0Blobs in Cosmological Galaxy Formation Simulations",
"author": [
{
"family_name": "Kimock",
"given_name": "Benjamin",
"orcid": "0000-0002-3160-7679",
"clpid": "Kimock-Benjamin"
},
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-Desika"
},
{
"family_name": "Smith",
"given_name": "Aaron",
"orcid": "0000-0002-2838-9033",
"clpid": "Smith-Aaron"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Bromm",
"given_name": "Volker",
"orcid": "0000-0003-0212-2979",
"clpid": "Bromm-Volker"
},
{
"family_name": "Dav\u00e9",
"given_name": "Romeel",
"orcid": "0000-0003-2842-9434",
"clpid": "Dav\u00e9-Romeel"
},
{
"family_name": "Geach",
"given_name": "James E.",
"orcid": "0000-0003-4964-4635",
"clpid": "Geach-James-E"
},
{
"family_name": "Hopkins",
"given_name": "Philip",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Keres\u0306",
"given_name": "Dus\u0306an",
"orcid": "0000-0002-1666-7067",
"clpid": "Keres\u0306-Dus\u0306an"
}
],
"abstract": "High-redshift Ly\u03b1 blobs (LABs) are an enigmatic class of objects that have been the subject of numerous observational and theoretical investigations. It is of particular interest to determine the dominant power sources for their luminosity, as direct emission from H ii regions, cooling gas, and fluorescence due to the presence of active galactic nuclei (AGNs) can all contribute significantly. In this paper, we present the first theoretical model to consider all of these physical processes in an attempt to develop a model for the origin of LABs. This is achieved by combining a series of high-resolution cosmological zoom-in simulations with ionization and Ly\u03b1 radiative transfer models. We find that massive galaxies display a range of Ly\u03b1 luminosities and spatial extents (which strongly depend on the limiting surface brightness used) over the course of their lives, though regularly exhibit luminosities and sizes consistent with observed LABs. The model LABs are typically powered from a combination of recombination in star-forming galaxies, as well as cooling emission from gas associated with accretion. When AGNs are included in the model, the fluorescence caused by active galactic nucleus-driven ionization can be a significant contributor to the total Ly\u03b1 luminosity as well. Within our modeled mass range, there are no obvious threshold physical properties that predict the appearance of LABs, and only weak correlations of the luminosity with the physical properties of the host galaxy. This is because the emergent Ly\u03b1 luminosity from a system is a complex function of the gas temperature, ionization state, and Ly\u03b1 escape fraction.",
"doi": "10.3847/1538-4357/abbe89",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2021-03-10",
"series_number": "2",
"volume": "909",
"issue": "2",
"pages": "Art. No. 119"
},
{
"id": "authors:f4m8m-wpj80",
"collection": "authors",
"collection_id": "f4m8m-wpj80",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200626-150127283",
"type": "article",
"title": "SatGen: a semi-analytical satellite galaxy generator \u2013 I. The model and its application to Local-Group satellite statistics",
"author": [
{
"family_name": "Jiang",
"given_name": "Fangzhou",
"orcid": "0000-0001-6115-0633",
"clpid": "Jiang-Fangzhou"
},
{
"family_name": "Dekel",
"given_name": "Avishai",
"orcid": "0000-0003-4174-0374",
"clpid": "Dekel-Avishai"
},
{
"family_name": "Freundlich",
"given_name": "Jonathan",
"orcid": "0000-0002-5245-7796",
"clpid": "Freundlich-Jonathan"
},
{
"family_name": "van den Bosch",
"given_name": "Frank C.",
"orcid": "0000-0003-3236-2068",
"clpid": "van-den-Bosch-F-C"
},
{
"family_name": "Green",
"given_name": "Sheridan B.",
"orcid": "0000-0001-9100-6237",
"clpid": "Green-Sheridan-B"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Benson",
"given_name": "Andrew",
"orcid": "0000-0001-5501-6008",
"clpid": "Benson-Andrew-J"
},
{
"family_name": "Du",
"given_name": "Xiaolong",
"clpid": "Du-Xiaolong"
}
],
"abstract": "We present a semi-analytical model of satellite galaxies, SatGen, which can generate large statistical samples of satellite populations for a host halo of desired mass, redshift, and assembly history. The model combines dark matter (DM) halo merger trees, empirical relations for the galaxy\u2013halo connection, and analytical prescriptions for tidal effects, dynamical friction, and ram-pressure stripping. SatGen emulates cosmological zoom-in hydrosimulations in certain aspects. Satellites can reside in cored or cuspy DM subhaloes, depending on the halo response to baryonic physics that can be formulated from hydrosimulations and physical modelling. The subhalo profile and the stellar mass and size of a satellite evolve depending on its tidal mass-loss and initial structure. The host galaxy can include a baryonic disc and a stellar bulge, each described by a density profile that allows analytic satellite orbit integration. SatGen complements simulations by propagating the effect of halo response found in simulated field galaxies to satellites (not properly resolved in simulations) and outperforms simulations by sampling the halo-to-halo variance of satellite statistics and overcoming artificial disruption due to insufficient resolution. As a first application, we use the model to study satellites of Milky Way (MW)- and M31-sized hosts, making it emulate simulations of bursty star formation and of smooth star formation, respectively, and to experiment with a disc potential in the host halo. We find that our model reproduces the observed satellite statistics reasonably well. Different physical recipes make a difference in satellite abundance and spatial distribution at the 25 per cent level, not large enough to be distinguished by current observations given the halo-to-halo variance. The MW/M31 disc depletes satellites by \u223c20 per cent and has a subtle effect of diversifying the internal structure of satellites, which is important for alleviating certain small-scale problems. We discuss the conditions for a massive satellite to survive in MW/M31.",
"doi": "10.1093/mnras/staa4034",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-03",
"series_number": "1",
"volume": "502",
"issue": "1",
"pages": "621-641"
},
{
"id": "authors:jnz2y-f0a57",
"collection": "authors",
"collection_id": "jnz2y-f0a57",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200310-082303427",
"type": "article",
"title": "Cosmic ray driven outflows to Mpc scales from L* galaxies",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
},
{
"family_name": "Hummels",
"given_name": "Cameron",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-C-B"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
}
],
"abstract": "We study the effects of cosmic rays (CRs) on outflows from star-forming galaxies in the circum and intergalactic medium (CGM/IGM), in high-resolution, fully cosmological FIRE-2 simulations (accounting for mechanical and radiative stellar feedback, magnetic fields, anisotropic conduction/viscosity/CR diffusion and streaming, and CR losses). We showed previously that massive (\u2060M_(halo)\u227310\u00b9\u00b9), low-redshift (z \u2272 1\u20132) haloes can have CR pressure dominate over thermal CGM pressure and balance gravity, giving rise to a cooler CGM with an equilibrium density profile. This dramatically alters outflows. Absent CRs, high gas thermal pressure in massive haloes 'traps' galactic outflows near the disc, so they recycle. With CRs injected in supernovae as modelled here, the low-pressure halo allows 'escape' and CR pressure gradients continuously accelerate this material well into the IGM in 'fast' outflows, while lower-density gas at large radii is accelerated in situ into 'slow' outflows that extend to >Mpc scales. CGM/IGM outflow morphologies are radically altered: they become mostly volume-filling (with inflow in a thin mid-plane layer) and coherently biconical from the disc to >Mpc. The CR-driven outflows are primarily cool (\u2060T\u223c10\u2075) and low velocity. All of these effects weaken and eventually vanish at lower halo masses (\u2060\u227210\u00b9\u00b9M\u2299\u2060) or higher redshifts (z \u2273 1\u20132), reflecting the ratio of CR to thermal + gravitational pressure in the outer halo. We present a simple analytical model that explains all of the above phenomena. We caution that these predictions may depend on uncertain CR transport physics.",
"doi": "10.1093/mnras/staa3690",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-03",
"series_number": "3",
"volume": "501",
"issue": "3",
"pages": "3640-3662"
},
{
"id": "authors:wv692-wvt49",
"collection": "authors",
"collection_id": "wv692-wvt49",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210507-085546557",
"type": "article",
"title": "A relationship between stellar metallicity gradients and galaxy age in dwarf galaxies",
"author": [
{
"family_name": "Mercado",
"given_name": "Francisco J.",
"orcid": "0000-0002-5908-737X",
"clpid": "Mercado-Francisco-J"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Moreno",
"given_name": "Jorge",
"orcid": "0000-0002-3430-3232",
"clpid": "Moreno-Jorge"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Graus",
"given_name": "Andrew S.",
"clpid": "Graus-Andrew-S"
},
{
"family_name": "Fitts",
"given_name": "Alex",
"orcid": "0000-0002-8928-6011",
"clpid": "Fitts-Alex"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Gurvich",
"given_name": "Alexander B.",
"orcid": "0000-0002-6145-3674",
"clpid": "Gurvich-Alexander-B"
}
],
"abstract": "We explore the origin of stellar metallicity gradients in simulated and observed dwarf galaxies. We use FIRE-2 cosmological baryonic zoom-in simulations of 26 isolated galaxies as well as existing observational data for 10 Local Group dwarf galaxies. Our simulated galaxies have stellar masses between 10^(5.5) and 10^(8.6)\u2009M\u2299. Whilst gas-phase metallicty gradients are generally weak in our simulated galaxies, we find that stellar metallicity gradients are common, with central regions tending to be more metal-rich than the outer parts. The strength of the gradient is correlated with galaxy-wide median stellar age, such that galaxies with younger stellar populations have flatter gradients. Stellar metallicty gradients are set by two competing processes: (1) the steady 'puffing' of old, metal-poor stars by feedback-driven potential fluctuations and (2) the accretion of extended, metal-rich gas at late times, which fuels late-time metal-rich star formation. If recent star formation dominates, then extended, metal-rich star formation washes out pre-existing gradients from the 'puffing' process. We use published results from ten Local Group dwarf galaxies to show that a similar relationship between age and stellar metallicity-gradient strength exists among real dwarfs. This suggests that observed stellar metallicity gradients may be driven largely by the baryon/feedback cycle rather than by external environmental effects.",
"doi": "10.1093/mnras/staa3958",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-03",
"series_number": "4",
"volume": "501",
"issue": "4",
"pages": "5121-5134"
},
{
"id": "authors:8x3tm-4rt38",
"collection": "authors",
"collection_id": "8x3tm-4rt38",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200309-153702109",
"type": "article",
"title": "Testing physical models for cosmic ray transport coefficients on galactic scales: self-confinement and extrinsic turbulence at \u223cGeV energies",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-Jonathan"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
}
],
"abstract": "The microphysics of \u223c\u2009GeV cosmic ray (CR) transport on galactic scales remain deeply uncertain, with almost all studies adopting simple prescriptions (e.g. constant diffusivity). We explore different physically motivated, anisotropic, dynamical CR transport scalings in high-resolution cosmological Feedback In Realistic Environment (FIRE) simulations of dwarf and \u223cL* galaxies where scattering rates vary with local plasma properties motivated by extrinsic turbulence (ET) or self-confinement (SC) scenarios, with varying assumptions about e.g. turbulent power spectra on un-resolved scales, Alfv\u00e9n-wave damping, etc. We self-consistently predict observables including \u03b3-rays (L\u03b3), grammage, residence times, and CR energy densities to constrain the models. We demonstrate many non-linear dynamical effects (not captured in simpler models) tend to enhance confinement. For example, in multiphase media, even allowing arbitrary fast transport in neutral gas does not substantially reduce CR residence times (or L_\u03b3), as transport is rate-limited by the ionized WIM and 'inner CGM' gaseous halo (10\u2074\u201310\u2076\u2009K gas within \u227210\u221230\u2009kpc), and L_\u03b3 can be dominated by trapping in small 'patches'. Most physical ET models contribute negligible scattering of \u223c1\u201310\u2009GeV CRs, but it is crucial to account for anisotropy and damping (especially of fast modes) or else scattering rates would violate observations. We show that the most widely assumed scalings for SC models produce excessive confinement by factors \u2273100 in the warm ionized medium (WIM) and inner CGM, where turbulent and Landau damping dominate. This suggests either a breakdown of quasi-linear theory used to derive the CR transport parameters in SC, or that other novel damping mechanisms dominate in intermediate-density ionized gas.",
"doi": "10.1093/mnras/staa3691",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-03",
"series_number": "3",
"volume": "501",
"issue": "3",
"pages": "4184-4213"
},
{
"id": "authors:wknv2-0es89",
"collection": "authors",
"collection_id": "wknv2-0es89",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200626-150130701",
"type": "article",
"title": "Effects of different cosmic ray transport models on galaxy formation",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-Jonathan"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
}
],
"abstract": "Cosmic rays (CRs) with \u223cGeV energies can contribute significantly to the energy and pressure budget in the interstellar, circumgalactic, and intergalactic medium (ISM, CGM, IGM). Recent cosmological simulations have begun to explore these effects, but almost all studies have been restricted to simplified models with constant CR diffusivity and/or streaming speeds. Physical models of CR propagation/scattering via extrinsic turbulence and self-excited waves predict transport coefficients which are complicated functions of local plasma properties. In a companion paper, we consider a wide range of observational constraints to identify proposed physically motivated cosmic ray propagation scalings which satisfy both detailed Milky Way (MW) and extragalactic \u03b3-ray constraints. Here, we compare the effects of these models relative to simpler 'diffusion+streaming' models on galaxy and CGM properties at dwarf through MW mass scales. The physical models predict large local variations in CR diffusivity, with median diffusivity increasing with galactocentric radii and decreasing with galaxy mass and redshift. These effects lead to a more rapid dropoff of CR energy density in the CGM (compared to simpler models), in turn producing weaker effects of CRs on galaxy star formation rates (SFRs), CGM absorption profiles, and galactic outflows. The predictions of the more physical CR models tend to lie 'in between' models which ignore CRs entirely and models which treat CRs with constant diffusivity.",
"doi": "10.1093/mnras/staa3692",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-03",
"series_number": "3",
"volume": "501",
"issue": "3",
"pages": "3663-3669"
},
{
"id": "authors:a9tfw-2q828",
"collection": "authors",
"collection_id": "a9tfw-2q828",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210222-084450592",
"type": "article",
"title": "Fiery Cores: Bursty and Smooth Star Formation Distributions across Galaxy Centers in Cosmological Zoom-in Simulations",
"author": [
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-Matthew-E"
},
{
"family_name": "Hatchfield",
"given_name": "H. Perry",
"orcid": "0000-0003-0946-4365",
"clpid": "Hatchfield-H-Perry"
},
{
"family_name": "Battersby",
"given_name": "Cara",
"orcid": "0000-0002-6073-9320",
"clpid": "Battersby-Cara"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Benincasa",
"given_name": "Samantha M.",
"orcid": "0000-0003-4826-9079",
"clpid": "Benincasa-Samantha-M"
},
{
"family_name": "Loebman",
"given_name": "Sarah R.",
"orcid": "0000-0003-3217-5967",
"clpid": "Loebman-Sarah-R"
},
{
"family_name": "Sormani",
"given_name": "Mattia C.",
"orcid": "0000-0001-6113-6241",
"clpid": "Sormani-Mattia-C"
},
{
"family_name": "Klessen",
"given_name": "Ralf S.",
"orcid": "0000-0002-0560-3172",
"clpid": "Klessen-Ralf-S"
}
],
"abstract": "We present an analysis of the R \u227e1.5 kpc core regions of seven simulated Milky Way-mass galaxies, from the FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulation suite, for a finely sampled period (\u0394t = 2.2 Myr) of 22 Myr at z \u2248 0, and compare them with star formation rate (SFR) and gas surface density observations of the Milky Way's Central Molecular Zone (CMZ). Despite not being tuned to reproduce the detailed structure of the CMZ, we find that four of these galaxies are consistent with CMZ observations at some point during this 22 Myr period. The galaxies presented here are not homogeneous in their central structures, roughly dividing into two morphological classes; (a) several of the galaxies have very asymmetric gas and SFR distributions, with intense (compact) starbursts occurring over a period of roughly 10 Myr, and structures on highly eccentric orbits through the CMZ, whereas (b) others have smoother gas and SFR distributions, with only slowly varying SFRs over the period analyzed. In class (a) centers, the orbital motion of gas and star-forming complexes across small apertures (R \u227e150 pc, analogously l < 1\u00b0 in the CMZ observations) contributes as much to tracers of star formation/dense gas appearing in those apertures, as the internal evolution of those structures does. These asymmetric/bursty galactic centers can simultaneously match CMZ gas and SFR observations, demonstrating that time-varying star formation can explain the CMZ's low star formation efficiency.",
"doi": "10.3847/2041-8213/abdebd",
"issn": "2041-8213",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2021-02-20",
"series_number": "2",
"volume": "908",
"issue": "2",
"pages": "Art. No. L31"
},
{
"id": "authors:hp2qb-c7x44",
"collection": "authors",
"collection_id": "hp2qb-c7x44",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210211-133104724",
"type": "article",
"title": "Realistic mock observations of the sizes and stellar mass surface densities of massive galaxies in FIRE-2 zoom-in simulations",
"author": [
{
"family_name": "Parsotan",
"given_name": "T.",
"orcid": "0000-0002-4299-2517",
"clpid": "Parsotan-Tyler"
},
{
"family_name": "Cochrane",
"given_name": "R. K.",
"orcid": "0000-0001-8855-6107",
"clpid": "Cochrane-Rachel-K"
},
{
"family_name": "Hayward",
"given_name": "C. C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "D.",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Feldmann",
"given_name": "R.",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "C. A.",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Wellons",
"given_name": "S.",
"orcid": "0000-0002-3977-2724",
"clpid": "Wellons-Sarah"
},
{
"family_name": "Hopkins",
"given_name": "P. F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "The galaxy size\u2013stellar mass and central surface density\u2013stellar mass relationships are fundamental observational constraints on galaxy formation models. However, inferring the physical size of a galaxy from observed stellar emission is non-trivial due to various observational effects, such as the mass-to-light ratio variations that can be caused by non-uniform stellar ages, metallicities, and dust attenuation. Consequently, forward-modelling light-based sizes from simulations is desirable. In this work, we use the SKIRT\u2009 dust radiative transfer code to generate synthetic observations of massive galaxies (\u2060M\u2217\u223c10\u00b9\u00b9M\u2299 at z = 2, hosted by haloes of mass M_(halo)\u223c10^(12.5)M\u2299\u2060) from high-resolution cosmological zoom-in simulations that form part of the Feedback In Realistic Environments project. The simulations used in this paper include explicit stellar feedback but no active galactic nucleus (AGN) feedback. From each mock observation, we infer the effective radius (R_e), as well as the stellar mass surface density within this radius and within 1kpc (\u03a3_e and \u03a3\u2081, respectively). We first investigate how well the intrinsic half-mass radius and stellar mass surface density can be inferred from observables. The majority of predicted sizes and surface densities are within a factor of 2 of the intrinsic values. We then compare our predictions to the observed size\u2013mass relationship and the \u03a3\u2081\u2212M\u22c6 and \u03a3_e\u2212M\u22c6 relationships. At z \u2273 2, the simulated massive galaxies are in general agreement with observational scaling relations. At z \u2272 2, they evolve to become too compact but still star forming, in the stellar mass and redshift regime where many of them should be quenched. Our results suggest that some additional source of feedback, such as AGN-driven outflows, is necessary in order to decrease the central densities of the simulated massive galaxies to bring them into agreement with observations at z \u2272 2.",
"doi": "10.1093/mnras/staa3765",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-02",
"series_number": "2",
"volume": "501",
"issue": "2",
"pages": "1591-1602"
},
{
"id": "authors:p4xn1-6gk41",
"collection": "authors",
"collection_id": "p4xn1-6gk41",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210114-164620520",
"type": "article",
"title": "Probing the CGM of low-redshift dwarf galaxies using FIRE simulations",
"author": [
{
"family_name": "Li",
"given_name": "Fei",
"clpid": "Li-Fei"
},
{
"family_name": "Rahman",
"given_name": "Mubdi",
"orcid": "0000-0003-1842-6096",
"clpid": "Rahman-Mubdi"
},
{
"family_name": "Murray",
"given_name": "Norman",
"orcid": "0000-0002-8659-3729",
"clpid": "Murray-Norman-W"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565",
"clpid": "Stern-Jonathan"
},
{
"family_name": "Hummels",
"given_name": "Cameron B.",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron-B"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
}
],
"abstract": "Observations of ultraviolet (UV) metal absorption lines have provided insight into the structure and composition of the circumgalactic medium (CGM) around galaxies. We compare these observations with the low-redshift (z \u2264 0.3) CGM around dwarf galaxies in high-resolution cosmological zoom-in runs in the FIRE-2 (Feedback In Realistic Environments) simulation suite. We select simulated galaxies that match the halo mass, stellar mass, and redshift of the observed samples. We produce absorption measurements using TRIDENT for UV transitions of C\u2009IV, O\u2009VI, Mg\u2009II, and Si\u2009III. The FIRE equivalent width (EW) distributions and covering fractions for the C\u2009IV ion are broadly consistent with observations inside 0.5R_(vir), but are underpredicted for O\u2009VI, Mg\u2009II, and Si\u2009III. The absorption strengths of the ions in the CGM are moderately correlated with the masses and star formation activity of the galaxies. The correlation strengths increase with the ionization potential of the ions. The structure and composition of the gas from the simulations exhibit three zones around dwarf galaxies characterized by distinct ion column densities: the discy interstellar medium, the inner CGM (the wind-dominated regime), and the outer CGM (the IGM accretion-dominated regime). We find that the outer CGM in the simulations is nearly but not quite supported by thermal pressure, so it is not in hydrostatic equilibrium, resulting in halo-scale bulk inflow and outflow motions. The net gas inflow rates are comparable to the star formation rate of the galaxy, but the bulk inflow and outflow rates are greater by an order of magnitude, with velocities comparable to the virial velocity of the halo. These roughly virial velocities (\u2060\u223c100 km s\u207b\u00b9\u2060) produce large EWs in the simulations. This supports a picture for dwarf galaxies in which the dynamics of the CGM at large scales are coupled to the small-scale star formation activity near the centre of their haloes.",
"doi": "10.1093/mnras/staa3322",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-01",
"series_number": "1",
"volume": "500",
"issue": "1",
"pages": "1038-1053"
},
{
"id": "authors:bwww3-z8y74",
"collection": "authors",
"collection_id": "bwww3-z8y74",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200626-150116926",
"type": "article",
"title": "The Keck Baryonic Structure Survey: using foreground/background galaxy pairs to trace the structure and kinematics of circumgalactic neutral hydrogen at z \u223c 2",
"author": [
{
"family_name": "Chen",
"given_name": "Yuguang",
"orcid": "0000-0003-4520-5395",
"clpid": "Chen-Yuguang"
},
{
"family_name": "Steidel",
"given_name": "Charles C.",
"orcid": "0000-0002-4834-7260",
"clpid": "Steidel-C-C"
},
{
"family_name": "Hummels",
"given_name": "Cameron B.",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron-B"
},
{
"family_name": "Rudie",
"given_name": "Gwen C.",
"orcid": "0000-0002-8459-5413",
"clpid": "Rudie-Gwen-C"
},
{
"family_name": "Dong",
"given_name": "Bili",
"clpid": "Dong-Bill"
},
{
"family_name": "Trainor",
"given_name": "Ryan F.",
"orcid": "0000-0002-6967-7322",
"clpid": "Trainor-Ryan-F"
},
{
"family_name": "Bogosavljevi\u0107",
"given_name": "Milan",
"orcid": "0000-0002-4710-4814",
"clpid": "Bogosavljevi\u0107-Milan"
},
{
"family_name": "Erb",
"given_name": "Dawn K.",
"orcid": "0000-0001-9714-2758",
"clpid": "Erb-Dawn-K"
},
{
"family_name": "Pettini",
"given_name": "Max",
"orcid": "0000-0002-5139-4359",
"clpid": "Pettini-Max"
},
{
"family_name": "Reddy",
"given_name": "Naveen A.",
"orcid": "0000-0001-9687-4973",
"clpid": "Reddy-Naveen-A"
},
{
"family_name": "Shapley",
"given_name": "Alice E.",
"orcid": "0000-0003-3509-4855",
"clpid": "Shapley-Alice-E"
},
{
"family_name": "Strom",
"given_name": "Allison L.",
"orcid": "0000-0001-6369-1636",
"clpid": "Strom-Allison-L"
},
{
"family_name": "Theios",
"given_name": "Rachel L.",
"orcid": "0000-0002-4236-1037",
"clpid": "Theios-Rachel-L"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
}
],
"abstract": "We present new measurements of the spatial distribution and kinematics of neutral hydrogen in the circumgalactic and intergalactic medium surrounding star-forming galaxies at z \u223c 2. Using the spectra of \u22433000 galaxies with redshifts \u3008z\u3009 = 2.3 \u00b1 0.4 from the Keck Baryonic Structure Survey, we assemble a sample of more than 200\u2009000 distinct foreground-background pairs with projected angular separations of 3\u2013500 arcsec and spectroscopic redshifts, with \u3008z_(fg)\u3009 = 2.23 and \u3008zbg\u3009 = 2.57 (foreground, background redshifts, respectively.) The ensemble of sightlines and foreground galaxies is used to construct a 2D map of the mean excess HI Ly\u03b1 optical depth relative to the intergalactic mean as a function of projected galactocentric distance (20 \u2272 D_(tran)/pkpc \u2272 4000) and line-of-sight velocity. We obtain accurate galaxy systemic redshifts, providing significant information on the line-of-sight kinematics of HI gas as a function of projected distance D_(tran). We compare the map with cosmological zoom-in simulation, finding qualitative agreement between them. A simple two-component (accretion, outflow) analytical model generally reproduces the observed line-of-sight kinematics and projected spatial distribution of HI. The best-fitting model suggests that galaxy-scale outflows with initial velocity v_(out) \u2243 600 km s\u207b\u00b9 dominate the kinematics of circumgalactic HI out to D_(tran) \u2243 50 kpc, while HI at D_(tran) \u2273 100 kpc is dominated by infall with characteristic v_(in) \u2272 circular velocity. Over the impact parameter range 80 \u2272 D_(tran)/pkpc \u2272 200, the HI line-of-sight velocity range reaches a minimum, with a corresponding flattening in the rest-frame Ly\u03b1 equivalent width. These observations can be naturally explained as the transition between outflow-dominated and accretion-dominated flows. Beyond D_(tran) \u2243 300\u2009pkpc (\u223c1\u2009cMpc), the line-of-sight kinematics are dominated by Hubble expansion.",
"doi": "10.1093/mnras/staa2808",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-12",
"series_number": "2",
"volume": "499",
"issue": "2",
"pages": "1721-1746"
},
{
"id": "authors:5e06r-3qg39",
"collection": "authors",
"collection_id": "5e06r-3qg39",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200626-150120381",
"type": "article",
"title": "Pressure balance in the multiphase ISM of cosmologically simulated disc galaxies",
"author": [
{
"family_name": "Gurvich",
"given_name": "Alexander B.",
"orcid": "0000-0002-6145-3674",
"clpid": "Gurvich-Alexander-B"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Richings",
"given_name": "Alexander J.",
"orcid": "0000-0003-0502-9235",
"clpid": "Richings-Alexander-J"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-Michael-Y"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Wellons",
"given_name": "Sarah",
"orcid": "0000-0002-3977-2724",
"clpid": "Wellons-Sarah"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565",
"clpid": "Stern-Jonathan"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-Matthew-E"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Loebman",
"given_name": "Sarah R.",
"clpid": "Loebman-Sarah-R"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-Norman-W"
}
],
"abstract": "Pressure balance plays a central role in models of the interstellar medium (ISM), but whether and how pressure balance is realized in a realistic multiphase ISM is not yet well understood. We address this question by using a set of FIRE-2 cosmological zoom-in simulations of Milky Way-mass disc galaxies, in which a multiphase ISM is self-consistently shaped by gravity, cooling, and stellar feedback. We analyse how gravity determines the vertical pressure profile as well as how the total ISM pressure is partitioned between different phases and components (thermal, dispersion/turbulence, and bulk flows). We show that, on average and consistent with previous more idealized simulations, the total ISM pressure balances the weight of the overlying gas. Deviations from vertical pressure balance increase with increasing galactocentric radius and with decreasing averaging scale. The different phases are in rough total pressure equilibrium with one another, but with large deviations from thermal pressure equilibrium owing to kinetic support in the cold and warm phases, which dominate the total pressure near the mid-plane. Bulk flows (e.g. inflows and fountains) are important at a few disc scale heights, while thermal pressure from hot gas dominates at larger heights. Overall, the total mid-plane pressure is well-predicted by the weight of the disc gas and we show that it also scales linearly with the star formation rate surface density (\u03a3_(SFR)). These results support the notion that the Kennicutt\u2013Schmidt relation arises because \u03a3_(SFR) and the gas surface density (\u03a3_g) are connected via the ISM mid-plane pressure.",
"doi": "10.1093/mnras/staa2578",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-11",
"series_number": "3",
"volume": "498",
"issue": "3",
"pages": "3664-3683"
},
{
"id": "authors:tjq7h-aa822",
"collection": "authors",
"collection_id": "tjq7h-aa822",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200310-084830640",
"type": "article",
"title": "Reproducing the CO-to-H\u2082 conversion factor in cosmological simulations of Milky-Way-mass galaxies",
"author": [
{
"family_name": "Keating",
"given_name": "Laura C.",
"orcid": "0000-0001-5211-1958",
"clpid": "Keating-Laura-C"
},
{
"family_name": "Richings",
"given_name": "Alexander J.",
"clpid": "Richings-Alexander-J"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-Norman-W"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Benincasa",
"given_name": "Samantha M.",
"orcid": "0000-0003-4826-9079",
"clpid": "Benincasa-Samantha-M"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Loebman",
"given_name": "Sarah",
"orcid": "0000-0003-3217-5967",
"clpid": "Loebman-Sarah-R"
},
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-Matthew-E"
}
],
"abstract": "We present models of CO(1\u20130) emission from Milky-Way-mass galaxies at redshift zero in the FIRE-2 cosmological zoom-in simulations. We calculate the molecular abundances by post-processing the simulations with an equilibrium chemistry solver while accounting for the effects of local sources, and determine the emergent CO(1\u20130) emission using a line radiative transfer code. We find that the results depend strongly on the shielding length assumed, which, in our models, sets the attenuation of the incident UV radiation field. At the resolution of these simulations, commonly used choices for the shielding length, such as the Jeans length, result in CO abundances that are too high at a given H\u2082 abundance. We find that a model with a distribution of shielding lengths, which has a median shielding length of \u223c3 pc in cold gas (T < 300 K) for both CO and H\u2082, is able to reproduce both the observed CO(1\u20130) luminosity and inferred CO-to-H\u2082 conversion factor at a given star formation rate compared with observations. We suggest that this short shielding length can be thought of as a subgrid model, which controls the amount of radiation that penetrates giant molecular clouds.",
"doi": "10.1093/mnras/staa2839",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-11",
"series_number": "1",
"volume": "499",
"issue": "1",
"pages": "837-850"
},
{
"id": "authors:tys13-3xx64",
"collection": "authors",
"collection_id": "tys13-3xx64",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-074106283",
"type": "article",
"title": "Evidence for a Vast Prograde Stellar Stream in the Solar Vicinity",
"author": [
{
"family_name": "Necib",
"given_name": "Lina",
"orcid": "0000-0003-2806-1414",
"clpid": "Necib-Lina"
},
{
"family_name": "Ostdiek",
"given_name": "Bryan",
"orcid": "0000-0002-0376-6461",
"clpid": "Ostdiek-Bryan"
},
{
"family_name": "Lisanti",
"given_name": "Mariangela",
"orcid": "0000-0002-8495-8659",
"clpid": "Lisanti-Mariangela"
},
{
"family_name": "Cohen",
"given_name": "Timothy",
"orcid": "0000-0002-7040-3038",
"clpid": "Cohen-Timothy"
},
{
"family_name": "Freytsis",
"given_name": "Marat",
"orcid": "0000-0002-6427-2895",
"clpid": "Freytsis-Marat"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Sanderson",
"given_name": "Robyn",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-Robyn-E"
}
],
"abstract": "Massive dwarf galaxies that merge with the Milky Way on prograde orbits can be dragged into the disk plane before being completely disrupted. Such mergers can contribute to an accreted stellar disk and a dark matter disk. Here we present Nyx, a vast stellar stream in the vicinity of the Sun, which provides the first indication that such an event occurred in the Milky Way. We identify about 200 stars that have coherent radial and prograde motion in this stream using a catalogue of accreted stars built by applying deep learning methods to the Gaia data. Taken together with chemical abundance and orbital information, these results strongly favour the interpretation that Nyx is the remnant of a disrupted dwarf galaxy. Further justified by FIRE hydrodynamic simulations, we demonstrate that prograde streams like Nyx can be found in the disk plane of galaxies and identified using our methods.",
"doi": "10.1038/s41550-020-1131-2",
"issn": "2397-3366",
"publisher": "Nature Publishing Group",
"publication": "Nature Astronomy",
"publication_date": "2020-11",
"series_number": "11",
"volume": "4",
"issue": "11",
"pages": "1078-1083"
},
{
"id": "authors:3vrwa-trt34",
"collection": "authors",
"collection_id": "3vrwa-trt34",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201209-153310187",
"type": "article",
"title": "The impact of AGN wind feedback in simulations of isolated galaxies with a multiphase ISM",
"author": [
{
"family_name": "Torrey",
"given_name": "Paul",
"orcid": "0000-0002-5653-0786",
"clpid": "Torrey-Paul"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Keres",
"given_name": "Dusan",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Murray",
"given_name": "Norm",
"clpid": "Murray-Norman-W"
}
],
"abstract": "Accreting black holes can drive fast and energetic nuclear winds that may be an important feedback mechanism associated with active galactic nuclei (AGN). In this paper, we implement a scheme for capturing feedback from these fast nuclear winds and examine their impact in simulations of isolated disc galaxies. Stellar feedback is modelled using the Feedback In Realistic Environments (FIRE) physics and produces a realistic multiphase interstellar medium (ISM). We find that AGN winds drive the formation of a low-density, high-temperature central gas cavity that is broadly consistent with analytic model expectations. The effects of AGN feedback on the host galaxy are a strong function of the wind kinetic power and momentum. Low- and moderate-luminosity AGN do not have a significant effect on their host galaxy: the AGN winds inefficiently couple to the ambient ISM and instead a significant fraction of their energy vents in the polar direction. For such massive black holes, accretion near the Eddington limit can have a dramatic impact on the host galaxy ISM: if AGN wind feedback acts for \u227320\u201330 Myr, the inner \u223c1\u201310 kpc of the ISM is disrupted and the global galaxy star formation rate is significantly reduced. We quantify the properties of the resulting galaxy-scale outflows and find that the radial momentum in the outflow is boosted by a factor of \u223c2\u20133 relative to that initially supplied in the AGN wind for strong feedback scenarios, decreasing below unity for less energetic winds. In contrast to observations, however, the outflows are primarily hot, with very little atomic or molecular gas. We conjecture that merging galaxies and high-redshift galaxies, which have more turbulent and thicker discs and very different nuclear gas geometries, may be even more disrupted by AGN winds than found in our simulations.",
"doi": "10.1093/mnras/staa2222",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-10-01",
"series_number": "4",
"volume": "497",
"issue": "4",
"pages": "5292-5308"
},
{
"id": "authors:38caq-nve32",
"collection": "authors",
"collection_id": "38caq-nve32",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200309-151230451",
"type": "article",
"title": "Physical models of streaming instabilities in protoplanetary discs",
"author": [
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-Jonathan"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We develop simple, physically motivated models for drag-induced dust\u2013gas streaming instabilities, which are thought to be crucial for clumping grains to form planetesimals in protoplanetary discs. The models explain, based on the physics of gaseous epicyclic motion and dust\u2013gas drag forces, the most important features of the streaming instability and its simple generalization, the disc settling instability. Some of the key properties explained by our models include the sudden change in the growth rate of the streaming instability when the dust-to-gas mass ratio surpasses one, the slow growth rate of the streaming instability compared to the settling instability for smaller grains, and the main physical processes underlying the growth of the most unstable modes in different regimes. As well as providing helpful simplified pictures for understanding the operation of an interesting and fundamental astrophysical fluid instability, our models may prove useful for analysing simulations and developing non-linear theories of planetesimal growth in discs.",
"doi": "10.1093/mnras/staa2311",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-10",
"series_number": "1",
"volume": "498",
"issue": "1",
"pages": "1239-1251"
},
{
"id": "authors:j6reg-kqs52",
"collection": "authors",
"collection_id": "j6reg-kqs52",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200626-150134129",
"type": "article",
"title": "No missing photons for reionization: moderate ionizing photon escape fractions from the FIRE-2 simulations",
"author": [
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
}
],
"abstract": "We present the escape fraction of hydrogen ionizing photons (f_(esc)) from a sample of 34 high-resolution cosmological zoom-in simulations of galaxies at z \u2265 5 in the Feedback in Realistic Environments project, post-processed with a Monte Carlo radiative transfer code for ionizing radiation. Our sample consists of 8500 haloes in M_(vir) \u223c 10\u2078\u201310\u00b9\u00b2M\u2299 (M* \u223c 10\u2074\u201310\u00b9\u2070M\u2299\u2060) at z = 5\u201312. We find the sample average\u3008f_(esc)\u3009increases with halo mass for M_(vir) \u223c 10\u2078\u201310^(9.5) M\u2299\u2060, becomes nearly constant for 10^(9.5)\u201310\u00b9\u00b9M\u2299, and decreases at \u227310\u00b9\u00b9M\u2299. Equivalently,\u3008f_(esc)\u3009 increases with stellar mass up to M\u2217 \u223c 10\u2078M\u2299 and decreases at higher masses. Even applying single-star stellar population synthesis models, we find a moderate\u3008f_(esc)\u3009\u223c 0.2 for galaxies at M\u2217 \u223c 10\u2078M\u2299\u2060. Nearly half of the escaped ionizing photons come from stars 1\u20133\u2009Myr old and the rest from stars 3\u201310\u2009Myr old. Binaries only have a modest effect, boosting\u3008f_(esc)\u3009by \u223c25\u201335 per cent and the number of escaped photons by 60\u201380 per cent. Most leaked ionizing photons are from vigorously star-forming regions that usually contain a feedback-driven kpc-scale superbubble surrounded by a dense shell. The shell is forming stars while accelerated, so new stars formed earlier in the shell are already inside the shell. Young stars in the bubble and near the edge of the shell can fully ionize some low-column-density paths pre-cleared by feedback, allowing a large fraction of their ionizing photons to escape. The decrease of\u3008f_(esc)\u3009at the high-mass end is due to dust attenuation, while at the low-mass end,\u3008f_(esc)\u3009decreases owing to inefficient star formation and hence feedback. At fixed mass,\u3008f_(esc)\u3009tends to increase with redshift. Although the absolute\u3008f_(esc)\u3009does not fully converge with resolution in our simulations, the mass- and redshift-dependence of\u3008f_(esc)\u3009 is likely robust. Our simulations produce sufficient ionizing photons for cosmic reionization.",
"doi": "10.1093/mnras/staa2404",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-10",
"series_number": "2",
"volume": "498",
"issue": "2",
"pages": "2001-2017"
},
{
"id": "authors:js7tw-ytw11",
"collection": "authors",
"collection_id": "js7tw-ytw11",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200311-130218946",
"type": "article",
"title": "Measuring dynamical masses from gas kinematics in simulated high-redshift galaxies",
"author": [
{
"family_name": "Wellons",
"given_name": "Sarah",
"orcid": "0000-0002-3977-2724",
"clpid": "Wellons-Sarah"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
}
],
"abstract": "Advances in instrumentation have recently extended detailed measurements of gas kinematics to large samples of high-redshift galaxies. Relative to most nearby, thin disc galaxies, in which gas rotation accurately traces the gravitational potential, the interstellar medium (ISM) of z \u2273 1 galaxies is typically more dynamic and exhibits elevated turbulence. If not properly modelled, these effects can strongly bias dynamical mass measurements. We use high-resolution FIRE-2 cosmological zoom-in simulations to analyse the physical effects that must be considered to correctly infer dynamical masses from gas kinematics. Our analysis covers a range of galaxy properties from low-redshift Milky-Way-mass galaxies to massive high-redshift galaxies (M\u22c6 > 10\u00b9\u00b9 M\u2299 at z = 1). Selecting only snapshots where a disc is present, we calculate the rotational profile v_\u03d5(r) of the cool (\u206010^(3.5) < T <10^(4.5) K\u2060) gas and compare it to the circular velocity v_c = \u221aGM_(enc)/r\u2060. In the simulated galaxies, the gas rotation traces the circular velocity at intermediate radii, but the two quantities diverge significantly in the centre and in the outer disc. Our simulations appear to over-predict observed rotational velocities in the centres of massive galaxies (likely from a lack of black hole feedback), so we focus on larger radii. Gradients in the turbulent pressure at these radii can provide additional radial support and bias dynamical mass measurements low by up to 40 per cent. In both the interior and exterior, the gas' motion can be significantly non-circular due to e.g. bars, satellites, and inflows/outflows. We discuss the accuracy of commonly used analytic models for pressure gradients (or 'asymmetric drift') in the ISM of high-redshift galaxies.",
"doi": "10.1093/mnras/staa2229",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-10",
"series_number": "4",
"volume": "497",
"issue": "4",
"pages": "4051-4065"
},
{
"id": "authors:znxmq-hgb43",
"collection": "authors",
"collection_id": "znxmq-hgb43",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200310-103921517",
"type": "article",
"title": "A Census of Sub-kiloparsec Resolution Metallicity Gradients in Star-forming Galaxies at Cosmic Noon from HST Slitless Spectroscopy",
"author": [
{
"family_name": "Wang",
"given_name": "Xin",
"orcid": "0000-0002-6180-0058",
"clpid": "Wang-Xin"
},
{
"family_name": "Jones",
"given_name": "Tucker A.",
"orcid": "0000-0001-5860-3419",
"clpid": "Jones-T-A"
},
{
"family_name": "Treu",
"given_name": "Tommaso",
"orcid": "0000-0002-8460-0390",
"clpid": "Treu-Tommaso"
},
{
"family_name": "Daddi",
"given_name": "Emanuele",
"orcid": "0000-0002-3331-9590",
"clpid": "Daddi-Emanuele"
},
{
"family_name": "Brammer",
"given_name": "Gabriel B.",
"orcid": "0000-0003-2680-005X",
"clpid": "Brammer-G-B"
},
{
"family_name": "Sharon",
"given_name": "Keren",
"orcid": "0000-0002-7559-0864",
"clpid": "Sharon-Keren"
},
{
"family_name": "Morishita",
"given_name": "Takahiro",
"orcid": "0000-0002-8512-1404",
"clpid": "Morishita-Takahiro"
},
{
"family_name": "Abramson",
"given_name": "Louis E.",
"orcid": "0000-0002-8860-1032",
"clpid": "Abramson-L-E"
},
{
"family_name": "Colbert",
"given_name": "James W.",
"clpid": "Colbert-J-W"
},
{
"family_name": "Henry",
"given_name": "Alaina L.",
"orcid": "0000-0002-6586-4446",
"clpid": "Henry-A-L"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Malkan",
"given_name": "Matthew A.",
"orcid": "0000-0001-6919-1237",
"clpid": "Malkan-M-A"
},
{
"family_name": "Schmidt",
"given_name": "Kasper B.",
"orcid": "0000-0002-3418-7251",
"clpid": "Schmidt-K-B"
},
{
"family_name": "Teplitz",
"given_name": "Harry I.",
"orcid": "0000-0002-7064-5424",
"clpid": "Teplitz-H-I"
},
{
"family_name": "Vulcani",
"given_name": "Benedetta",
"orcid": "0000-0003-0980-1499",
"clpid": "Vulcani-Benedetta"
}
],
"abstract": "We present the hitherto largest sample of gas-phase metallicity radial gradients measured at sub-kpc resolution in star-forming galaxies in the redshift range of z \u2208 [1.2, 2.3]. These measurements are enabled by the synergy of slitless spectroscopy from the Hubble Space Telescope near-infrared channels and the lensing magnification from foreground galaxy clusters. Our sample consists of 76 galaxies with stellar mass ranging from 10\u2077 to 10\u00b9\u2070 M_\u2299, an instantaneous star formation rate in the range of [1, 100] M_\u2299 yr\u207b\u00b9, and global metallicity [1/12, 2] of solar. At a 2\u03c3 confidence level, 15/76 galaxies in our sample show negative radial gradients, whereas 7/76 show inverted gradients. Combining ours and all other metallicity gradients obtained at a similar resolution currently available in the literature, we measure a negative mass dependence of \u0394log(O/H)/ \u0394r [dex kpc\u207b\u00b9] = (\u22120.020 \u00b1 0.007) + (\u22120.016 \u00b1 0.008) log(M_\u2217/10^(9.4) M_\u2299), with the intrinsic scatter being \u03c3 = 0.060 \u00b1 0.006 over 4 orders of magnitude in stellar mass. Our result is consistent with strong feedback, not secular processes, being the primary governor of the chemostructural evolution of star-forming galaxies during the disk mass assembly at cosmic noon. We also find that the intrinsic scatter of metallicity gradients increases with decreasing stellar mass and increasing specific star formation rate. This increase in the intrinsic scatter is likely caused by the combined effect of cold-mode gas accretion and merger-induced starbursts, with the latter more predominant in the dwarf mass regime of M\u2217 \u2272 10\u2079 M_\u2299.",
"doi": "10.3847/1538-4357/abacce",
"issn": "1538-4357",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2020-09-10",
"series_number": "2",
"volume": "900",
"issue": "2",
"pages": "Art. No. 183"
},
{
"id": "authors:xkx3s-ym751",
"collection": "authors",
"collection_id": "xkx3s-ym751",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200626-150123820",
"type": "article",
"title": "A dark matter profile to model diverse feedback-induced core sizes of \u039bCDM haloes",
"author": [
{
"family_name": "Lazar",
"given_name": "Alexandres",
"orcid": "0000-0002-6852-6282",
"clpid": "Lazar-Alexandres"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Graus",
"given_name": "Andrew S.",
"clpid": "Graus-Andrew-S"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-Coral-R"
},
{
"family_name": "Straight",
"given_name": "Maria C.",
"clpid": "Straight-Maria-C"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Fitts",
"given_name": "Alex",
"orcid": "0000-0002-8928-6011",
"clpid": "Fitts-Alex"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
}
],
"abstract": "We analyse the cold dark matter density profiles of 54 galaxy haloes simulated with Feedback In Realistic Environments (FIRE)-2 galaxy formation physics, each resolved within 0.5 per cent of the halo virial radius. These haloes contain galaxies with masses that range from ultrafaint dwarfs (\u2060M\u22c6 \u2243 10^(4.5) M_\u2299\u2060) to the largest spirals (\u2060M\u22c6 \u2243 10\u00b9\u00b9 M_\u2299\u2060) and have density profiles that are both cored and cuspy. We characterize our results using a new, analytic density profile that extends the standard two-parameter Einasto form to allow for a pronounced constant density core in the resolved innermost radius. With one additional core-radius parameter, r_c, this three-parameter core-Einasto profile is able to characterize our feedback-impacted dark matter haloes more accurately than other three-parameter profiles proposed in the literature. To enable comparisons with observations, we provide fitting functions for r_c and other profile parameters as a function of both M\u22c6 and M\u22c6/M_(halo). In agreement with past studies, we find that dark matter core formation is most efficient at the characteristic stellar-to-halo mass ratio M\u22c6/M_(halo) \u2243 5 \u00d7 10\u207b\u00b3, or M\u22c6 \u223c 10\u2079 M_\u2299\u2060, with cores that are roughly the size of the galaxy half-light radius, r_c \u2243 1\u22125\u2009kpc. Furthermore, we find no evidence for core formation at radii \u2273100 pc in galaxies with M\u22c6/M_(halo) < 5 \u00d7 10\u207b\u2074 or M\u22c6 \u2272 10\u2076 M_\u2299\u2060. For Milky Way-size galaxies, baryonic contraction often makes haloes significantly more concentrated and dense at the stellar half-light radius than DMO runs. However, even at the Milky Way scale, FIRE-2 galaxy formation still produces small dark matter cores of \u2243 0.5\u22122\u2009kpc in size. Recent evidence for a \u223c2\u2009kpc core in the Milky Way's dark matter halo is consistent with this expectation.",
"doi": "10.1093/mnras/staa2101",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-09",
"series_number": "2",
"volume": "497",
"issue": "2",
"pages": "2393-2417"
},
{
"id": "authors:j4wr5-r7r35",
"collection": "authors",
"collection_id": "j4wr5-r7r35",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200310-100838684",
"type": "article",
"title": "Live Fast, Die Young: GMC lifetimes in the FIRE cosmological simulations of Milky Way-mass galaxies",
"author": [
{
"family_name": "Benincasa",
"given_name": "Samantha M.",
"orcid": "0000-0003-4826-9079",
"clpid": "Benincasa-Samantha-M"
},
{
"family_name": "Loebman",
"given_name": "Sarah R.",
"orcid": "0000-0003-3217-5967",
"clpid": "Loebman-Sarah-R"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-Norman-W"
},
{
"family_name": "Bellardini",
"given_name": "Matthew A.",
"clpid": "Bellardini-Matthew-A"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D\u00e1vid"
},
{
"family_name": "Orr",
"given_name": "Matthew",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-Matthew-E"
}
],
"abstract": "We present the first measurement of the lifetimes of giant molecular clouds (GMCs) in cosmological simulations at z = 0, using the Latte suite of FIRE-2 simulations of Milky Way (MW) mass galaxies. We track GMCs with total gas mass \u227310\u2075 M\u2299 at high spatial (\u223c1 pc), mass (7100 M\u2299), and temporal (1 Myr) resolution. Our simulated GMCs are consistent with the distribution of masses for massive GMCs in the MW and nearby galaxies. We find GMC lifetimes of 5\u20137 Myr, or 1\u20132 freefall times, on average, with less than 2 per\u2009cent of clouds living longer than 20 Myr. We find decreasing GMC lifetimes with increasing virial parameter, and weakly increasing GMC lifetimes with galactocentric radius, implying that environment affects the evolutionary cycle of GMCs. However, our GMC lifetimes show no systematic dependence on GMC mass or amount of star formation. These results are broadly consistent with inferences from the literature and provide an initial investigation into ultimately understanding the physical processes that govern GMC lifetimes in a cosmological setting.",
"doi": "10.1093/mnras/staa2116",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-09",
"series_number": "3",
"volume": "497",
"issue": "3",
"pages": "3993-3999"
},
{
"id": "authors:2adhz-52103",
"collection": "authors",
"collection_id": "2adhz-52103",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200310-145036739",
"type": "article",
"title": "Properties of the circumgalactic medium in cosmic ray-dominated galaxy haloes",
"author": [
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Hummels",
"given_name": "Cameron B.",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-C-B"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565",
"clpid": "Stern-J"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
}
],
"abstract": "We investigate the impact of cosmic rays (CRs) on the circumgalactic medium (CGM) in FIRE-2 simulations, for ultra-faint dwarf through Milky Way (MW)-mass haloes hosting star-forming (SF) galaxies. Our CR treatment includes injection by supernovae, anisotropic streaming and diffusion along magnetic field lines, and collisional and streaming losses, with constant parallel diffusivity \u03ba\u223c3\u00d710\u00b2\u2079 cm\u00b2 s\u207b\u00b9 chosen to match \u03b3-ray observations. With this, CRs become more important at larger halo masses and lower redshifts, and dominate the pressure in the CGM in MW-mass haloes at z \u2272 1\u20132. The gas in these 'CR-dominated' haloes differs significantly from runs without CRs: the gas is primarily cool (a few \u223c10\u2074), and the cool phase is volume-filling and has a thermal pressure below that needed for virial or local thermal pressure balance. Ionization of the 'low' and 'mid' ions in this diffuse cool gas is dominated by photoionization, with O\u2009VI columns \u227310^(14.5) cm\u207b\u00b2 at distances \u2273150kpc\u2060. CR and thermal gas pressure are locally anticorrelated, maintaining total pressure balance, and the CGM gas density profile is determined by the balance of CR pressure gradients and gravity. Neglecting CRs, the same haloes are primarily warm/hot (\u2060T\u227310\u2075) with thermal pressure balancing gravity, collisional ionization dominates, O\u2009VI columns are lower and Ne\u2009VIII higher, and the cool phase is confined to dense filaments in local thermal pressure equilibrium with the hot phase.",
"doi": "10.1093/mnras/staa1849",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-08",
"series_number": "4",
"volume": "496",
"issue": "4",
"pages": "4221-4238"
},
{
"id": "authors:j9j18-md006",
"collection": "authors",
"collection_id": "j9j18-md006",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200903-100107610",
"type": "article",
"title": "Swirls of FIRE: spatially resolved gas velocity dispersions and star formation rates in FIRE-2 disc environments",
"author": [
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-M-E"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Medling",
"given_name": "Anne M.",
"orcid": "0000-0001-7421-2944",
"clpid": "Medling-A-M"
},
{
"family_name": "Gurvich",
"given_name": "Alexander B.",
"orcid": "0000-0002-6145-3674",
"clpid": "Gurvich-A-B"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
},
{
"family_name": "Pineda",
"given_name": "Jorge L.",
"orcid": "0000-0001-8898-2800",
"clpid": "Pineda-J-L"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Su",
"given_name": "Kung-Yi",
"orcid": "0000-0003-1598-0083",
"clpid": "Su-Kung-Yi"
}
],
"abstract": "We study the spatially resolved (sub-kpc) gas velocity dispersion (\u03c3)\u2013star formation rate (SFR) relation in the FIRE-2 (Feedback in Realistic Environments) cosmological simulations. We specifically focus on Milky Way-mass disc galaxies at late times (z \u2248 0). In agreement with observations, we find a relatively flat relationship, with \u03c3 \u2248 15\u201330 km\u2009s\u207b\u00b9 in neutral gas across 3 dex in SFRs. We show that higher dense gas fractions (ratios of dense gas to neutral gas) and SFRs are correlated at constant \u03c3. Similarly, lower gas fractions (ratios of gas to stellar mass) are correlated with higher \u03c3 at constant SFR. The limits of the \u03c3\u2013\u03a3_(SFR) relation correspond to the onset of strong outflows. We see evidence of 'on-off' cycles of star formation in the simulations, corresponding to feedback injection time-scales of 10\u2013100 Myr, where SFRs oscillate about equilibrium SFR predictions. Finally, SFRs and velocity dispersions in the simulations agree well with feedback-regulated and marginally stable gas disc (Toomre's Q = 1) model predictions, and the simulation data effectively rule out models assuming that gas turns into stars at (low) constant efficiency (i.e. 1 per\u2009cent per free-fall time). And although the simulation data do not entirely exclude gas accretion/gravitationally powered turbulence as a driver of \u03c3, it appears to be subdominant to stellar feedback in the simulated galaxy discs at z \u2248 0.",
"doi": "10.1093/mnras/staa1619",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-08",
"series_number": "2",
"volume": "496",
"issue": "2",
"pages": "1620-1637"
},
{
"id": "authors:qnb92-zmp27",
"collection": "authors",
"collection_id": "qnb92-zmp27",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-092908062",
"type": "article",
"title": "Simulating the Diverse Instabilities of Dust in Magnetized Gas",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-J"
},
{
"family_name": "Seligman",
"given_name": "Darryl",
"orcid": "0000-0002-0726-6480",
"clpid": "Seligman-D"
}
],
"abstract": "Recently, Squire & Hopkins showed that charged dust grains moving through magnetized gas under the influence of a uniform external force (such as radiation pressure or gravity) are subject to a spectrum of instabilities. Qualitatively distinct instability families are associated with different Alfv\u00e9n or magnetosonic waves and drift or gyro motion. We present a suite of simulations exploring these instabilities, for grains in a homogeneous medium subject to an external acceleration. We vary parameters such as the ratio of Lorentz-to-drag forces on dust, plasma \u03b2, size scale, and acceleration. All regimes studied drive turbulent motions and dust-to-gas fluctuations in the saturated state, rapidly amplify magnetic fields into equipartition with velocity fluctuations, and produce instabilities that persist indefinitely (despite random grain motions). Different parameters produce diverse morphologies and qualitatively different features in dust, but the saturated gas state can be broadly characterized as anisotropic magnetosonic or Alfv\u00e9nic turbulence. Quasi-linear theory can qualitatively predict the gas turbulent properties. Turbulence grows from small to large scales, and larger scale modes usually drive more vigorous gas turbulence, but dust velocity and density fluctuations are more complicated. In many regimes, dust forms structures (clumps, filaments, sheets) that reach extreme overdensities (up to \u226b10\u2079 times mean), and exhibit substantial substructure even in nearly incompressible gas. These can be even more prominent at lower dust-to-gas ratios. In other regimes, dust self-excites scattering via magnetic fluctuations that isotropize and amplify dust velocities, producing fast, diffusive dust motions.",
"doi": "10.1093/mnras/staa1046",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-08",
"series_number": "2",
"volume": "496",
"issue": "2",
"pages": "2123-2154"
},
{
"id": "authors:khwjg-bpv43",
"collection": "authors",
"collection_id": "khwjg-bpv43",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200310-083102875",
"type": "article",
"title": "Can magnetized turbulence set the mass scale of stars?",
"author": [
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D\u00e1vid"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-Michael-Y"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Offner",
"given_name": "Stella S. R.",
"orcid": "0000-0003-1252-9916",
"clpid": "Offner-Stella-S-R"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
}
],
"abstract": "Understanding the evolution of self-gravitating, isothermal, magnetized gas is crucial for star formation, as these physical processes have been postulated to set the initial mass function (IMF). We present a suite of isothermal magnetohydrodynamic (MHD) simulations using the GIZMO code that follow the formation of individual stars in giant molecular clouds (GMCs), spanning a range of Mach numbers found in observed GMCs (\u2060M\u223c10\u221250\u2060). As in past works, the mean and median stellar masses are sensitive to numerical resolution, because they are sensitive to low-mass stars that contribute a vanishing fraction of the overall stellar mass. The mass-weighted median stellar mass M\u2085\u2080 becomes insensitive to resolution once turbulent fragmentation is well resolved. Without imposing Larson-like scaling laws, our simulations find M\u2085\u2080\u221d\u223cM\u2080M\u207b\u00b3\u03b1_(turb)SFE^(1/3) for GMC mass M\u2080, sonic Mach number M\u2060, virial parameter \u03b1_(turb), and star formation efficiency SFE = M\u22c6/M\u2080. This fit agrees well with previous IMF results from the RAMSES, ORION2, and SPHNG codes. Although M\u2085\u2080 has no significant dependence on the magnetic field strength at the cloud scale, MHD is necessary to prevent a fragmentation cascade that results in non-convergent stellar masses. For initial conditions and SFE similar to star-forming GMCs in our Galaxy, we predict M\u2085\u2080 to be >20M\u2299\u2060, an order of magnitude larger than observed (\u2060\u223c2M\u2299\u2060), together with an excess of brown dwarfs. Moreover, M\u2085\u2080 is sensitive to initial cloud properties and evolves strongly in time within a given cloud, predicting much larger IMF variations than are observationally allowed. We conclude that physics beyond MHD turbulence and gravity are necessary ingredients for the IMF.",
"doi": "10.1093/mnras/staa1883",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-08",
"series_number": "4",
"volume": "496",
"issue": "4",
"pages": "5072-5088"
},
{
"id": "authors:spcv7-fac36",
"collection": "authors",
"collection_id": "spcv7-fac36",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200310-093310026",
"type": "article",
"title": "The Bolometric Quasar Luminosity Function at z = 0-7",
"author": [
{
"family_name": "Shen",
"given_name": "Xuejian",
"orcid": "0000-0002-6196-823X",
"clpid": "Shen-Xuejian"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Alexander",
"given_name": "D. M.",
"orcid": "0000-0002-5896-6313",
"clpid": "Alexander-D-M"
},
{
"family_name": "Richards",
"given_name": "Gordon T.",
"clpid": "Richards-G-T"
},
{
"family_name": "Ross",
"given_name": "Nicholas P.",
"orcid": "0000-0003-1830-6473",
"clpid": "Ross-N-P"
},
{
"family_name": "Hickox",
"given_name": "R. C.",
"orcid": "0000-0003-1468-9526",
"clpid": "Hickox-R-C"
}
],
"abstract": "In this paper, we provide updated constraints on the bolometric quasar luminosity function (QLF) from z = 0 to z = 7. The constraints are based on an observational compilation that includes observations in the rest-frame IR, B band, UV, soft, and hard X-ray in past decades. Our method follows Hopkins et al. with an updated quasar SED model and bolometric and extinction corrections. The new best-fitting bolometric quasar luminosity function behaves qualitatively different from the old Hopkins model at high redshift. Compared with the old model, the number density normalization decreases towards higher redshift and the bright-end slope is steeper at z \u2273 2. Due to the paucity of measurements at the faint end, the faint end slope at z \u2273 5 is quite uncertain. We present two models, one featuring a progressively steeper faint-end slope at higher redshift and the other featuring a shallow faint-end slope at z \u2273 5. Further multiband observations of the faint-end QLF are needed to distinguish between these models. The evolutionary pattern of the bolometric QLF can be interpreted as an early phase likely dominated by the hierarchical assembly of structures and a late phase likely dominated by the quenching of galaxies. We explore the implications of this model on the ionizing photon production by quasars, the CXB spectrum, the SMBH mass density, and mass functions. The predicted hydrogen photoionization rate contributed by quasars is subdominant during the epoch of reionization and only becomes important at z \u2272 3. The predicted CXB spectrum, cosmic SMBH mass density, and SMBH mass function are generally consistent with existing observations.",
"doi": "10.1093/mnras/staa1381",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-07",
"series_number": "3",
"volume": "495",
"issue": "3",
"pages": "3252-3275"
},
{
"id": "authors:xrey4-gfs55",
"collection": "authors",
"collection_id": "xrey4-gfs55",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200310-111822630",
"type": "article",
"title": "A general-purpose time-step criterion for simulations with gravity",
"author": [
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-M-Y"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We describe a new adaptive time-step criterion for integrating gravitational motion, which uses the tidal tensor to estimate the local dynamical time-scale and scales the time-step proportionally. This provides a better candidate for a truly general-purpose gravitational time-step criterion than the usual prescription derived from the gravitational acceleration, which does not respect the equivalence principle, breaks down when a=0\u2060, and does not obey the same dimensional scaling as the true time-scale of orbital motion. We implement the tidal time-step criterion in the simulation code GIZMO, and examine controlled tests of collisionless galaxy and star cluster models, as well as galaxy merger simulations. The tidal criterion estimates the dynamical time faithfully, and generally provides a more efficient time-stepping scheme compared to an acceleration criterion. Specifically, the tidal criterion achieves order-of-magnitude smaller energy errors for the same number of force evaluations in potentials with inner profiles shallower than \u03c1 \u221d r\u207b\u00b9 (i.e. where a \u2192 0\u2060), such as star clusters and cored galaxies. For a given problem these advantages must be weighed against the additional overhead of computing the tidal tensor on-the-fly, but in many cases this overhead is small.",
"doi": "10.1093/mnras/staa1453",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-07",
"series_number": "4",
"volume": "495",
"issue": "4",
"pages": "4306-4313"
},
{
"id": "authors:8hh4d-fdd59",
"collection": "authors",
"collection_id": "8hh4d-fdd59",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200310-140049842",
"type": "article",
"title": "Stellar feedback sets the universal acceleration scale in galaxies",
"author": [
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-M-Y"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "It has been established for decades that rotation curves deviate from the Newtonian gravity expectation given baryons alone below a characteristic acceleration scale g\u2020\u223c10\u207b\u2078 cm s\u207b\u00b2\u2060, a scale promoted to a new fundamental constant in MOND. In recent years, theoretical and observational studies have shown that the star formation efficiency (SFE) of dense gas scales with surface density, SFE \u223c \u03a3/\u03a3_(crit) with \u03a3_(crit)\u223c\u27e8p\u02d9/m\u2217\u27e9/(\u03c0G)\u223c1000 M_\u2299 pc\u207b\u00b2 (where \u27e8p\u02d9/m\u2217\u27e9 is the momentum flux output by stellar feedback per unit stellar mass in a young stellar population). We argue that the SFE, more generally, should scale with the local gravitational acceleration, i.e. that SFE \u223cg_(tot)/g_(crit) \u2261 (GM_(tot)/R\u00b2)/\u27e8p\u02d9/m\u2217\u27e9\u2060, where M_(tot) is the total gravitating mass and g_(crit) = \u27e8p\u02d9/m\u2217\u27e9 = \u03c0G\u03a3_(crit) \u2248 10\u207b\u2078 cm s\u207b\u00b2 \u2248 g\u2020. Hence, the observed g\u2020 may correspond to the characteristic acceleration scale above which stellar feedback cannot prevent efficient star formation, and baryons will eventually come to dominate. We further show how this may give rise to the observed acceleration scaling g_(obs) \u223c (g_(baryon)g\u2020)^(1/2) (where g_(baryon) is the acceleration due to baryons alone) and flat rotation curves. The derived characteristic acceleration g\u2020 can be expressed in terms of fundamental constants (gravitational constant, proton mass, and Thomson cross-section): g\u2020\u223c0.1Gmp_/\u03c3_T\u2060.",
"doi": "10.1093/mnrasl/slaa103",
"issn": "1745-3925",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society: Letters",
"publication_date": "2020-07",
"series_number": "1",
"volume": "496",
"issue": "1",
"pages": "L127-L132"
},
{
"id": "authors:292cx-grz11",
"collection": "authors",
"collection_id": "292cx-grz11",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200625-112849542",
"type": "article",
"title": "Most stars (and planets?) are born in intense radiation fields",
"author": [
{
"family_name": "Lee",
"given_name": "Eve J.",
"orcid": "0000-0002-1228-9820",
"clpid": "Lee-Eve-J"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Protostars and young stars are strongly spatially 'clustered' or 'correlated' within their natal giant molecular clouds. We demonstrate that such clustering leads to the conclusion that the incident bolometric radiative flux upon a random young star/disc is enhanced (relative to volume-averaged fluxes) by a factor that increases with the total stellar mass of the complex. Because the Galactic cloud mass function is top-heavy, the typical star in our Galaxy experienced a much stronger radiative environment than those forming in well-observed nearby (but relatively small) clouds, exceeding fluxes in the Orion Nebular Cluster by factors of \u227330. Heating of the circumstellar disc around a median young star is dominated by this external radiation beyond \u223c50 au. And if discs are not well shielded by ambient dust, external ultraviolet irradiation can dominate over the host star down to sub-au scales. Another consequence of stellar clustering is an extremely broad Galaxy-wide distribution of incident flux (spanning >10 decades), with half the Galactic star formation in a substantial 'tail' towards even more intense background radiation. We also show that the strength of external irradiation is amplified superlinearly in high-density environments such as the Galactic Centre, starbursts, or high-redshift galaxies.",
"doi": "10.1093/mnrasl/slaa050",
"issn": "1745-3925",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society: Letters",
"publication_date": "2020-06-11",
"series_number": "1",
"volume": "495",
"issue": "1",
"pages": "L86-L91"
},
{
"id": "authors:xjdc0-8h184",
"collection": "authors",
"collection_id": "xjdc0-8h184",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200310-095909852",
"type": "article",
"title": "Stars made in outflows may populate the stellar halo of the Milky Way",
"author": [
{
"family_name": "Yu",
"given_name": "Sijie",
"orcid": "0000-0002-1019-0341",
"clpid": "Yu-Sijie"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-J-S"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Sanderson",
"given_name": "Robyn E.",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-R-E"
},
{
"family_name": "Graus",
"given_name": "Andrew S.",
"clpid": "Graus-A-S"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Nierenberg",
"given_name": "Anna M.",
"clpid": "Nierenberg-A-M"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-M-Y"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
}
],
"abstract": "We study stellar-halo formation using six Milky-Way-mass galaxies in FIRE-2 cosmological zoom simulations. We find that 5\u221240 per cent of the outer (50\u2013300 kpc) stellar halo in each system consists of in-situ stars that were born in outflows from the main galaxy. Outflow stars originate from gas accelerated by superbubble winds, which can be compressed, cool, and form co-moving stars. The majority of these stars remain bound to the halo and fall back with orbital properties similar to the rest of the stellar halo at z = 0. In the outer halo, outflow stars are more spatially homogeneous, metal-rich, and alpha-element-enhanced than the accreted stellar halo. At the solar location, up to \u223c10 per cent of our kinematically identified halo stars were born in outflows; the fraction rises to as high as \u223c40 per cent for the most metal-rich local halo stars ([Fe/H] >\u22120.5). Such stars can be retrograde and create features similar to the recently discovered Milky Way 'Splash' in phase space. We conclude that the Milky Way stellar halo could contain local counterparts to stars that are observed to form in molecular outflows in distant galaxies. Searches for such a population may provide a new, near-field approach to constraining feedback and outflow physics. A stellar halo contribution from outflows is a phase-reversal of the classic halo formation scenario of Eggen, Lynden-Bell & Sandange, who suggested that halo stars formed in rapidly infalling gas clouds. Stellar outflows may be observable in direct imaging of external galaxies and could provide a source for metal-rich, extreme-velocity stars in the Milky Way.",
"doi": "10.1093/mnras/staa522",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-05",
"series_number": "2",
"volume": "494",
"issue": "2",
"pages": "1539-1559"
},
{
"id": "authors:gp2q7-cec47",
"collection": "authors",
"collection_id": "gp2q7-cec47",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-080442014",
"type": "article",
"title": "Cataloging Accreted Stars within Gaia DR2 using Deep Learning",
"author": [
{
"family_name": "Ostdiek",
"given_name": "B.",
"clpid": "Ostdiek-B"
},
{
"family_name": "Necib",
"given_name": "L.",
"orcid": "0000-0003-2806-1414",
"clpid": "Necib-L"
},
{
"family_name": "Cohen",
"given_name": "T.",
"clpid": "Cohen-T"
},
{
"family_name": "Freytsis",
"given_name": "M.",
"clpid": "Freytsis-M"
},
{
"family_name": "Lisanti",
"given_name": "M.",
"clpid": "Lisanti-M"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "S.",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Wetzel",
"given_name": "A.",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Sanderson",
"given_name": "R. E.",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-R-E"
},
{
"family_name": "Hopkins",
"given_name": "P. F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Aims. The goal of this study is to present the development of a machine learning based approach that utilizes phase space alone to separate the Gaia DR2 stars into two categories: those accreted onto the Milky Way from those that are in situ. Traditional selection methods that have been used to identify accreted stars typically rely on full 3D velocity, metallicity information, or both, which significantly reduces the number of classifiable stars. The approach advocated here is applicable to a much larger portion of Gaia DR2. \n\nMethods. A method known as \"transfer learning\" is shown to be effective through extensive testing on a set of mock Gaia catalogs that are based on the FIRE cosmological zoom-in hydrodynamic simulations of Milky Way-mass galaxies. The machine is first trained on simulated data using only 5D kinematics as inputs and is then further trained on a cross-matched Gaia/RAVE data set, which improves sensitivity to properties of the real Milky Way. \n\nResults. The result is a catalog that identifies \u223c767\u2006000 accreted stars within Gaia DR2. This catalog can yield empirical insights into the merger history of the Milky Way and could be used to infer properties of the dark matter distribution.",
"doi": "10.1051/0004-6361/201936866",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy and Astrophysics",
"publication_date": "2020-04",
"volume": "636",
"pages": "Art. No. A75"
},
{
"id": "authors:qgf1e-zn144",
"collection": "authors",
"collection_id": "qgf1e-zn144",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-093900885",
"type": "article",
"title": "Self-consistent proto-globular cluster formation in cosmological simulations of high-redshift galaxies",
"author": [
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-M-Y"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Kim",
"given_name": "Ji-Hoon",
"orcid": "0000-0003-4464-1160",
"clpid": "Kim-Ji-Hoon"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "We report the formation of bound star clusters in a sample of high-resolution cosmological zoom-in simulations of z \u2265 5 galaxies from the Feedback In Realistic Environments project. We find that bound clusters preferentially form in high-pressure clouds with gas surface densities over 10\u2074M\u2299pc\u207b\u00b2\u2060, where the cloud-scale star formation efficiency is near unity and young stars born in these regions are gravitationally bound at birth. These high-pressure clouds are compressed by feedback-driven winds and/or collisions of smaller clouds/gas streams in highly gas-rich, turbulent environments. The newly formed clusters follow a power-law mass function of dN/dM \u223c M\u207b\u00b2. The cluster formation efficiency is similar across galaxies with stellar masses of \u223c10\u2077\u201310\u00b9\u2070M\u2299 at z \u2265 5. The age spread of cluster stars is typically a few Myr and increases with cluster mass. The metallicity dispersion of cluster members is \u223c0.08\u2009dex in [Z/H] and does not depend on cluster mass significantly. Our findings support the scenario that present-day old globular clusters (GCs) were formed during relatively normal star formation in high-redshift galaxies. Simulations with a stricter/looser star formation model form a factor of a few more/fewer bound clusters per stellar mass formed, while the shape of the mass function is unchanged. Simulations with a lower local star formation efficiency form more stars in bound clusters. The simulated clusters are larger than observed GCs due to finite resolution. Our simulations are among the first cosmological simulations that form bound clusters self-consistently in a wide range of high-redshift galaxies.",
"doi": "10.1093/mnras/staa527",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-04",
"series_number": "3",
"volume": "493",
"issue": "3",
"pages": "4315-4332"
},
{
"id": "authors:xggxd-wyy98",
"collection": "authors",
"collection_id": "xggxd-wyy98",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190729-112957859",
"type": "article",
"title": "But What About... Cosmic Rays, Magnetic Fields, Conduction, & Viscosity in Galaxy Formation",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Ji",
"given_name": "Suoqing",
"orcid": "0000-0001-9658-0588",
"clpid": "Ji-Suoqing"
},
{
"family_name": "Su",
"given_name": "Kung-Yi",
"orcid": "0000-0003-1598-0083",
"clpid": "Su-Kung-Yi"
},
{
"family_name": "Hummels",
"given_name": "Cameron B.",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-C-B"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
}
],
"abstract": "We present and study a large suite of high-resolution cosmological zoom-in simulations, using the FIRE-2 treatment of mechanical and radiative feedback from massive stars, together with explicit treatment of magnetic fields, anisotropic conduction and viscosity (accounting for saturation and limitation by plasma instabilities at high \u03b2), and cosmic rays (CRs) injected in supernovae shocks (including anisotropic diffusion, streaming, adiabatic, hadronic and Coulomb losses). We survey systems from ultrafaint dwarf (\u2060M\u2217\u223c10\u2074M\u2299\u2060, M_(halo)\u223c10\u2079M\u2299\u2060) through Milky Way/Local Group (MW/LG) masses, systematically vary uncertain CR parameters (e.g. the diffusion coefficient \u03ba and streaming velocity), and study a broad ensemble of galaxy properties [masses, star formation (SF) histories, mass profiles, phase structure, morphologies, etc.]. We confirm previous conclusions that magnetic fields, conduction, and viscosity on resolved (\u2060\u22731\u2009pc) scales have only small effects on bulk galaxy properties. CRs have relatively weak effects on all galaxy properties studied in dwarfs (\u2060M\u2217\u226a10\u00b9\u2070M\u2299, M_(halo)\u227210\u00b9\u00b9M\u2299\u2060), or at high redshifts (z \u2273 1\u20132), for any physically reasonable parameters. However, at higher masses (\u2060M_(halo)\u227310\u00b9\u00b9M\u2299) and z \u2272 1\u20132, CRs can suppress SF and stellar masses by factors \u223c2\u20134, given reasonable injection efficiencies and relatively high effective diffusion coefficients \u03ba\u22733\u00d710\u00b2\u2079cm\u00b2s\u207b\u00b9\u2060. At lower \u03ba, CRs take too long to escape dense star-forming gas and lose their energy to collisional hadronic losses, producing negligible effects on galaxies and violating empirical constraints from spallation and \u03b3-ray emission. At much higher \u03ba CRs escape too efficiently to have appreciable effects even in the CGM. But around \u03ba\u223c3\u00d710\u00b2\u2079cm\u00b2s\u207b\u00b9\u2060, CRs escape the galaxy and build up a CR-pressure-dominated halo which maintains approximate virial equilibrium and supports relatively dense, cool (T \u226a 10\u2076\u2009K) gas that would otherwise rain on to the galaxy. CR 'heating' (from collisional and streaming losses) is never dominant.",
"doi": "10.1093/mnras/stz3321",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-03",
"series_number": "3",
"volume": "492",
"issue": "3",
"pages": "3465-3498"
},
{
"id": "authors:0f2fc-nem17",
"collection": "authors",
"collection_id": "0f2fc-nem17",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200227-100225727",
"type": "article",
"title": "On the survival of cool clouds in the circumgalactic medium",
"author": [
{
"family_name": "Li",
"given_name": "Zhihui",
"orcid": "0000-0001-5113-7558",
"clpid": "Li-Zhihui"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-J"
},
{
"family_name": "Hummels",
"given_name": "Cameron",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-C-B"
}
],
"abstract": "We explore the survival of cool clouds in multiphase circumgalactic media. We revisit the 'cloud-crushing problem' in a large survey of simulations including radiative cooling, self-shielding, self-gravity, magnetic fields, and anisotropic Braginskii conduction and viscosity (with saturation). We explore a wide range of parameters including cloud size, velocity, ambient temperature and density, and a variety of magnetic field configurations and cloud turbulence. We find that realistic magnetic fields and turbulence have weaker effects on cloud survival; the most important physics is radiative cooling and conduction. Self-gravity and self-shielding are important for clouds that are initially Jeans-unstable, but largely irrelevant otherwise. Non-self-gravitating, realistically magnetized clouds separate into four regimes: (1) at low column densities, clouds evaporate rapidly via conduction; (2) a 'failed pressure confinement' regime, where the ambient hot gas cools too rapidly to provide pressure confinement for the cloud; (3) an 'infinitely long-lived' regime, in which the cloud lifetime becomes longer than the cooling time of gas swept up in the leading bow shock, so the cloud begins to accrete and grow; and (4) a 'classical cloud destruction' regime, where clouds are eventually destroyed by instabilities. In the final regime, the cloud lifetime can exceed the naive cloud-crushing time owing to conduction-induced compression. However, small and/or slow-moving clouds can also evaporate more rapidly than the cloud-crushing time. We develop simple analytic models that explain the simulated cloud destruction times in this regime.",
"doi": "10.1093/mnras/stz3567",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-02",
"series_number": "2",
"volume": "492",
"issue": "2",
"pages": "1841-1854"
},
{
"id": "authors:hzq3w-a2z94",
"collection": "authors",
"collection_id": "hzq3w-a2z94",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105644699",
"type": "article",
"title": "Radiative Stellar Feedback in Galaxy Formation: Methods and Physics",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"clpid": "Grudi\u0107-M-Y"
},
{
"family_name": "Wetzel",
"given_name": "Andrew R.",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
},
{
"family_name": "Butcher",
"given_name": "Nathan",
"clpid": "Butcher-N"
}
],
"abstract": "Radiative feedback (RFB) from stars plays a key role in galaxies, but remains poorly understood. We explore this using high-resolution, multifrequency radiation-hydrodynamics (RHD) simulations from the Feedback In Realistic Environments (FIRE) project. We study ultrafaint dwarf through Milky Way mass scales, including H+He photoionization; photoelectric, Lyman Werner, Compton, and dust heating; and single+multiple scattering radiation pressure (RP). We compare distinct numerical algorithms: ray-based LEBRON (exact when optically thin) and moments-based M1 (exact when optically thick). The most important RFB channels on galaxy scales are photoionization heating and single-scattering RP: in all galaxies, most ionizing/far-UV luminosity (\u223c1/2 of lifetime-integrated bolometric) is absorbed. In dwarfs, the most important effect is photoionization heating from the UV background suppressing accretion. In MW-mass galaxies, metagalactic backgrounds have negligible effects; but local photoionization and single-scattering RP contribute to regulating the galactic star formation efficiency and lowering central densities. Without some RFB (or other 'rapid' FB), resolved GMCs convert too-efficiently into stars, making galaxies dominated by hyperdense, bound star clusters. This makes star formation more violent and 'bursty' when SNe explode in these hyperclustered objects: thus, including RFB 'smoothes' SFHs. These conclusions are robust to RHD methods, but M1 produces somewhat stronger effects. Like in previous FIRE simulations, IR multiple-scattering is rare (negligible in dwarfs, \u223c10 per cent of RP in massive galaxies): absorption occurs primarily in 'normal' GMCs with A_V \u223c 1.",
"doi": "10.1093/mnras/stz3129",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-01",
"series_number": "3",
"volume": "491",
"issue": "3",
"pages": "3702-3729"
},
{
"id": "authors:mz8jx-gwn38",
"collection": "authors",
"collection_id": "mz8jx-gwn38",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105651728",
"type": "article",
"title": "Cosmic Rays or Turbulence can Suppress Cooling Flows (Where Thermal Heating or Momentum Injection Fail)",
"author": [
{
"family_name": "Su",
"given_name": "Kung-Yi",
"clpid": "Su-Kung-Yi"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-M-E"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Robles",
"given_name": "Victor H.",
"orcid": "0000-0002-9497-9963",
"clpid": "Robles-V-H"
}
],
"abstract": "The quenching 'maintenance' and 'cooling flow' problems are important from the Milky Way through massive cluster elliptical galaxies. Previous work has shown that some source of energy beyond that from stars and pure magnetohydrodynamic processes is required, perhaps from active galactic nuclei, but even the qualitative form of this energetic input remains uncertain. Different scenarios include thermal 'heating', direct wind or momentum injection, cosmic ray heating or pressure support, or turbulent 'stirring' of the intracluster medium (ICM). We investigate these in 10\u00b9\u00b2\u221210\u00b9\u2074M\u2299 haloes using high-resolution non-cosmological simulations with the FIRE-2 (Feedback In Realistic Environments) stellar feedback model, including simplified toy energy injection models, where we arbitrarily vary the strength, injection scale, and physical form of the energy. We explore which scenarios can quench without violating observational constraints on energetics or ICM gas. We show that turbulent stirring in the central \u223c100 kpc, or cosmic ray injection, can both maintain a stable low-star formation rate halo for >Gyr time-scales with modest energy input, by providing a non-thermal pressure that stably lowers the core density and cooling rates. In both cases, associated thermal-heating processes are negligible. Turbulent stirring preserves cool-core features while mixing condensed core gas into the hotter halo and is by far the most energy efficient model. Pure thermal heating or nuclear isotropic momentum injection require vastly larger energy, are less efficient in lower mass haloes, easily overheat cores, and require fine tuning to avoid driving unphysical temperature gradients or gas expulsion from the halo centre.",
"doi": "10.1093/mnras/stz3011",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-01",
"series_number": "1",
"volume": "491",
"issue": "1",
"pages": "1190-1212"
},
{
"id": "authors:s88qv-qab93",
"collection": "authors",
"collection_id": "s88qv-qab93",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-095255751",
"type": "article",
"title": "A profile in FIRE: resolving the radial distributions of satellite galaxies in the Local Group with simulations",
"author": [
{
"family_name": "Samuel",
"given_name": "Jenna",
"orcid": "0000-0002-8429-4100",
"clpid": "Samuel-Jenna"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Tollerud",
"given_name": "Erik",
"orcid": "0000-0002-9599-310X",
"clpid": "Tollerud-Erik-J"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
},
{
"family_name": "Loebman",
"given_name": "Sarah",
"orcid": "0000-0003-3217-5967",
"clpid": "Loebman-Sarah-R"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Benincasa",
"given_name": "Samantha",
"orcid": "0000-0003-4826-9079",
"clpid": "Benincasa-Samantha-M"
},
{
"family_name": "Bailin",
"given_name": "Jeremy",
"clpid": "Bailin-Jeremy"
}
],
"abstract": "While many tensions between Local Group (LG) satellite galaxies and \u039b cold dark matter cosmology have been alleviated through recent cosmological simulations, the spatial distribution of satellites remains an important test of physical models and physical versus numerical disruption in simulations. Using the FIRE-2 cosmological zoom-in baryonic simulations, we examine the radial distributions of satellites with M\u2217>10\u2075 M\u2299 around eight isolated Milky Way (MW) mass host galaxies and four hosts in LG-like pairs. We demonstrate that these simulations resolve the survival and physical destruction of satellites with M\u2217\u227310\u2075\u2009M\u2299. The simulations broadly agree with LG observations, spanning the radial profiles around the MW and M31. This agreement does not depend strongly on satellite mass, even at distances \u2272100 kpc. Host-to-host variation dominates the scatter in satellite counts within 300 kpc of the hosts, while time variation dominates scatter within 50 kpc. More massive host galaxies within our sample have fewer satellites at small distances, likely because of enhanced tidal destruction of satellites via the baryonic discs of host galaxies. Furthermore, we quantify and provide fits to the tidal depletion of subhaloes in baryonic relative to dark matter-only simulations as a function of distance. Our simulated profiles imply observational incompleteness in the LG even at M\u2217\u227310\u2075 M\u2299: we predict 2\u201310 such satellites to be discovered around the MW and possibly 6\u20139 around M31. To provide cosmological context, we compare our results with the radial profiles of satellites around MW analogues in the SAGA survey, finding that our simulations are broadly consistent with most SAGA systems.",
"doi": "10.1093/mnras/stz3054",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2020-01",
"series_number": "1",
"volume": "491",
"issue": "1",
"pages": "1471-1490"
},
{
"id": "authors:rh6xq-26g82",
"collection": "authors",
"collection_id": "rh6xq-26g82",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105555952",
"type": "article",
"title": "Synthetic Gaia surveys from the FIRE cosmological simulations of Milky-Way-mass galaxies",
"author": [
{
"family_name": "Sanderson",
"given_name": "Robyn E.",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-Robyn-E"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Loebman",
"given_name": "Sarah",
"orcid": "0000-0003-3217-5967",
"clpid": "Loebman-Sarah-R"
},
{
"family_name": "Sharma",
"given_name": "Sanjib",
"orcid": "0000-0002-0920-809X",
"clpid": "Sharma-Sanjib"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
}
],
"abstract": "With Gaia Data Release 2, the astronomical community is entering a new era of multidimensional surveys of the Milky Way. This new phase-space view of our Galaxy demands new tools for comparing observations to simulations of Milky Way-mass galaxies in a cosmological context, to test the physics of both dark matter and galaxy formation. We present ananke, a framework for generating synthetic phase-space surveys from high-resolution baryonic simulations, and use it to generate a suite of synthetic surveys resembling Gaia DR2 in data structure, magnitude limits, and observational errors. We use three cosmological simulations of Milky Way-mass galaxies from the Latte suite of the Feedback In Realistic Environments project, which feature self-consistent clustering of star formation in dense molecular clouds and thin stellar/gaseous disks in live cosmological halos with satellite dwarf galaxies and stellar halos. We select three solar viewpoints from each simulation to generate nine synthetic Gaia-like surveys. We sample synthetic stars by assuming each star particle (of mass 7070 M\u2299) represents a single stellar population. At each viewpoint, we compute dust extinction from the simulated gas metallicity distribution and apply a simple error model to produce a synthetic Gaia-like survey that includes both observational properties and a pointer to the generating star particle. We provide the complete simulation snapshot at z = 0 for each simulated galaxy. We describe data access points, the data model, and plans for future upgrades. These synthetic surveys provide a tool for the scientific community to test analysis methods and interpret Gaia data.",
"doi": "10.3847/1538-4365/ab5b9d",
"issn": "1538-4365",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Supplement Series",
"publication_date": "2020-01",
"series_number": "1",
"volume": "246",
"issue": "1",
"pages": "Art. No. 6"
},
{
"id": "authors:0g77y-6tw87",
"collection": "authors",
"collection_id": "0g77y-6tw87",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191216-145833165",
"type": "article",
"title": "High-redshift Galaxy Formation with Self-consistently Modeled Stars and Massive Black Holes: Stellar Feedback and Quasar Growth",
"author": [
{
"family_name": "Kim",
"given_name": "Ji-hoon",
"orcid": "0000-0003-4464-1160",
"clpid": "Kim-Ji-hoon"
},
{
"family_name": "Wise",
"given_name": "John H.",
"orcid": "0000-0003-1173-8847",
"clpid": "Wise-J-H"
},
{
"family_name": "Abel",
"given_name": "Tom",
"orcid": "0000-0002-5969-1251",
"clpid": "Abel-T"
},
{
"family_name": "Jo",
"given_name": "Yongseok",
"orcid": "0000-0003-3977-1761",
"clpid": "Jo-Yongseok"
},
{
"family_name": "Primack",
"given_name": "Joel R.",
"orcid": "0000-0001-5091-5098",
"clpid": "Primack-J-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "As computational resolution of modern cosmological simulations come closer to resolving individual star-forming clumps in a galaxy, the need for \"resolution-appropriate\" physics for a galaxy-scale simulation has never been greater. To this end, we introduce a self-consistent numerical framework that includes explicit treatments of feedback from star-forming molecular clouds (SFMCs) and massive black holes (MBHs). In addition to the thermal supernovae feedback from SFMC particles, photoionizing radiation from both SFMCs and MBHs is tracked through full three-dimensional ray tracing. A mechanical feedback channel from MBHs is also considered. Using our framework, we perform a state-of-the-art cosmological simulation of a quasar-host galaxy at z ~ 7.5 for ~25 Myr with all relevant galactic components, such as dark matter, gas, SFMCs, and an embedded MBH seed of \u227310\u2076 M\u2299. We find that feedback from SFMCs and an accreting MBH suppresses runaway star formation locally in the galactic core region. Newly included radiation feedback from SFMCs, combined with feedback from the MBH, helps the MBH grow faster by retaining gas that eventually accretes on to the MBH. Our experiment demonstrates that previously undiscussed types of interplay between gas, SFMCs, and a MBH may hold important clues about the growth and feedback of quasars and their host galaxies in the high-redshift universe.",
"doi": "10.3847/1538-4357/ab510b",
"issn": "1538-4357",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2019-12-20",
"series_number": "2",
"volume": "887",
"issue": "2",
"pages": "Art. No. 120"
},
{
"id": "authors:p5d50-p5929",
"collection": "authors",
"collection_id": "p5d50-p5929",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200109-143244679",
"type": "article",
"title": "Star formation at the edge of the Local Group: a rising star formation history in the isolated galaxy WLM",
"author": [
{
"family_name": "Albers",
"given_name": "Saundra M.",
"orcid": "0000-0001-5496-2668",
"clpid": "Albers-S-M"
},
{
"family_name": "Weisz",
"given_name": "Daniel R.",
"orcid": "0000-0002-6442-6030",
"clpid": "Weisz-D-R"
},
{
"family_name": "Cole",
"given_name": "Andrew A.",
"orcid": "0000-0003-0303-3855",
"clpid": "Cole-A-A"
},
{
"family_name": "Dolphin",
"given_name": "Andrew E.",
"orcid": "0000-0001-8416-4093",
"clpid": "Dolphin-A-E"
},
{
"family_name": "Skillman",
"given_name": "Evan D.",
"clpid": "Skillman-E-D"
},
{
"family_name": "Williams",
"given_name": "Benjamin F.",
"orcid": "0000-0002-7502-0597",
"clpid": "Williams-B-F"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-J-S"
},
{
"family_name": "Dalcanton",
"given_name": "Julianne J.",
"clpid": "Dalcanton-J-J"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Leaman",
"given_name": "Ryan",
"clpid": "Leaman-R"
},
{
"family_name": "McConnachie",
"given_name": "Alan W.",
"clpid": "McConnachie-A-W"
},
{
"family_name": "Vogelsberger",
"given_name": "Mark",
"orcid": "0000-0001-8593-7692",
"clpid": "Vogelsberger-M"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
}
],
"abstract": "We present the star formation history (SFH) of the isolated (D \u223c 970 kpc) Local Group dwarf galaxy Wolf\u2013Lundmark\u2013Melotte (WLM) measured from colour\u2013magnitude diagrams (CMDs) constructed from deep Hubble Space Telescope imaging. Our observations include a central (\u20600.5r_h\u2060) and outer field (\u20600.7r_h\u2060) that reach below the oldest main-sequence turn-off. WLM has no early dominant episode of star formation: 20 per cent of its stellar mass formed by \u223c12.5 Gyr ago (\u2060z \u223c 5). It also has an SFR that rises to the present with 50 per cent of the stellar mass within the most recent 5 Gyr (\u2060z < 0.7). There is evidence of a strong age gradient: the mean age of the outer field is 5 Gyr older than the inner field despite being only 0.4 kpc apart. Some models suggest such steep gradients are associated with strong stellar feedback and dark-matter core creation. The SFHs of real isolated dwarf galaxies and those from the Feedback in Realistic Environment suite are in good agreement for M\u22c6(\u2060z = 0) \u223c 10\u2077\u201310\u2079 M_\u2299, but in worse agreement at lower masses (\u2060M\u22c6(z=0)\u223c10\u2075\u221210\u2077 M_\u2299\u2060). These differences may be explainable by systematics in the models (e.g. reionization model) and/or observations (HST field placement). We suggest that a coordinated effort to get deep CMDs between HST/JWST (crowded central fields) and WFIRST (wide-area halo coverage) is the optimal path for measuring global SFHs of isolated dwarf galaxies.",
"doi": "10.1093/mnras/stz2903",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-12",
"series_number": "4",
"volume": "490",
"issue": "4",
"pages": "5538-5550"
},
{
"id": "authors:t2w2e-27p02",
"collection": "authors",
"collection_id": "t2w2e-27p02",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105648233",
"type": "article",
"title": "Be it therefore resolved: cosmological simulations of dwarf galaxies with 30 solar mass resolution",
"author": [
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-C"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Pace",
"given_name": "Andrew B.",
"orcid": "0000-0002-6021-8760",
"clpid": "Pace-A-B"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-J-S"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
}
],
"abstract": "We study a suite of extremely high-resolution cosmological Feedback in Realistic Environments simulations of dwarf galaxies (\u2060M_(halo) \u2272 10\u00b9\u2070 M\u2299\u2060), run to z = 0 with 30M\u2299 resolution, sufficient (for the first time) to resolve the internal structure of individual supernovae remnants within the cooling radius. Every halo with M_(halo) \u2273 10_(8.6) M\u2299 is populated by a resolved stellar galaxy, suggesting very low-mass dwarfs may be ubiquitous in the field. Our ultra-faint dwarfs (UFDs; M\u2217 < 10\u2075 M\u2299\u2060) have their star formation (SF) truncated early (z \u2273 2), likely by reionization, while classical dwarfs (\u2060M\u2217 > 10\u2075 M\u2299) continue forming stars to z < 0.5. The systems have bursty star formation histories, forming most of their stars in periods of elevated SF strongly clustered in both space and time. This allows our dwarf with M*/M_(halo) > 10\u207b\u2074 to form a dark matter core > 200pc, while lower mass UFDs exhibit cusps down to \u2272 100pc\u2060, as expected from energetic arguments. Our dwarfs with M\u2217 > 10\u2084 M\u2299 have half-mass radii (R_(1/2)) in agreement with Local Group (LG) dwarfs (dynamical mass versus R_(1/2) and stellar rotation also resemble observations). The lowest mass UFDs are below surface brightness limits of current surveys but are potentially visible in next-generation surveys (e.g. LSST). The stellar metallicities are lower than in LG dwarfs; this may reflect pre-enrichment of the LG by the massive hosts or Pop-III stars. Consistency with lower resolution studies implies that our simulations are numerically robust (for a given physical model).",
"doi": "10.1093/mnras/stz2887",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-12",
"series_number": "3",
"volume": "490",
"issue": "3",
"pages": "4447-4463"
},
{
"id": "authors:mtqdq-6an51",
"collection": "authors",
"collection_id": "mtqdq-6an51",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105636977",
"type": "article",
"title": "Dwarf Galaxies in CDM, WDM, and SIDM: Disentangling Baryons and Dark Matter Physics",
"author": [
{
"family_name": "Fitts",
"given_name": "Alex",
"orcid": "0000-0002-8928-6011",
"clpid": "Fitts-Alex"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Bozek",
"given_name": "Brandon",
"clpid": "Bozek-Brandon"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Graus",
"given_name": "Andrew",
"clpid": "Graus-Andrew-S"
},
{
"family_name": "Robles",
"given_name": "Victor H.",
"orcid": "0000-0002-9497-9963",
"clpid": "Robles-Victor-H"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
}
],
"abstract": "We present a suite of FIRE-2 cosmological zoom-in simulations of isolated field dwarf galaxies, all with masses of M_(halo) \u2248 10\u00b9\u2070 M_\u2299 at z = 0, across a range of dark matter models. For the first time, we compare how both self-interacting dark matter (SIDM) and/or warm dark matter (WDM) models affect the assembly histories as well as the central density structure in fully hydrodynamical simulations of dwarfs. Dwarfs with smaller stellar half-mass radii (r_(1/2) < 500 pc) have lower \u03c3\u22c6/V_(max) ratios, reinforcing the idea that smaller dwarfs may reside in haloes that are more massive than is naively expected. The majority of dwarfs simulated with self-interactions actually experience contraction of their inner density profiles with the addition of baryons relative to the cores produced in dark-matter-only runs, though the simulated dwarfs are always less centrally dense than in \u039bCDM. The V_(1/2)\u2013r_(1/2) relation across all simulations is generally consistent with observations of Local Field dwarfs, though compact objects such as Tucana provide a unique challenge. Overall, the inclusion of baryons substantially reduces any distinct signatures of dark matter physics in the observable properties of dwarf galaxies. Spatially resolved rotation curves in the central regions (<400 pc) of small dwarfs could provide a way to distinguish between CDM, WDM, and SIDM, however: at the masses probed in this simulation suite, cored density profiles in dwarfs with small r_(1/2) values can only originate from dark matter self-interactions.",
"doi": "10.1093/mnras/stz2613",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-11",
"series_number": "1",
"volume": "490",
"issue": "1",
"pages": "962-977"
},
{
"id": "authors:aee4n-pxr73",
"collection": "authors",
"collection_id": "aee4n-pxr73",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105702036",
"type": "article",
"title": "A Predicted Correlation Between Age Gradient and Star Formation History in FIRE Dwarf Galaxies",
"author": [
{
"family_name": "Graus",
"given_name": "Andrew S.",
"clpid": "Graus-A-S"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-J-S"
},
{
"family_name": "Fitts",
"given_name": "Alex",
"orcid": "0000-0002-8928-6011",
"clpid": "Fitts-A"
},
{
"family_name": "Cooper",
"given_name": "Michael C.",
"orcid": "0000-0003-1371-6019",
"clpid": "Cooper-M-C"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Weisz",
"given_name": "Daniel R.",
"orcid": "0000-0002-6442-6030",
"clpid": "Weisz-D-R"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "We explore the radial variation of star formation histories (SFHs) in dwarf galaxies simulated with Feedback In Realistic Environments (FIRE) physics. The sample contains 26 field dwarf galaxies with M_(star) = 10\u2075\u201310\u2079 M\u2299. We find age gradients are common in our dwarfs, with older stars dominant at large radii. The strength of the gradient correlates with overall galaxy age such that earlier star formation produces a more pronounced gradient. The relation between formation time and strength of the gradient is driven by both mergers and star formation feedback. Mergers can both steepen and flatten the age gradient depending on the timing of the merger and SFHs of the merging galaxy. In galaxies without significant mergers, feedback pushes stars to the outskirts. The strength of the age gradient is determined by the subsequent evolution of the galaxy. Galaxies with weak age gradients constantly grow to z = 0, meaning that young star formation occurs at a similar radius to which older stars are heated to. In contrast, galaxies with strong age gradients tend to maintain a constant half-mass radius over time. If real galaxies have age gradients as we predict, stellar population studies that rely on sampling a limited fraction of a galaxy can give a biased view of its global SFH. Central fields can be biased young by Gyrs while outer fields are biased old. Fields positioned near the 2D half-light radius will provide the least biased measure of a dwarf galaxy's global SFH.",
"doi": "10.1093/mnras/stz2649",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-11",
"series_number": "1",
"volume": "490",
"issue": "1",
"pages": "1186-1201"
},
{
"id": "authors:r2smq-c1266",
"collection": "authors",
"collection_id": "r2smq-c1266",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191025-090648233",
"type": "article",
"title": "Star formation histories of dwarf galaxies in the FIRE simulations: dependence on mass and Local Group environment",
"author": [
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Sanderson",
"given_name": "Robyn",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-Robyn-E"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Graus",
"given_name": "Andrew",
"clpid": "Graus-Andrew-S"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Fitts",
"given_name": "Alex",
"orcid": "0000-0002-8928-6011",
"clpid": "Fitts-Alex"
},
{
"family_name": "Samuel",
"given_name": "Jenna",
"orcid": "0000-0002-8429-4100",
"clpid": "Samuel-Jenna"
},
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-Coral-R"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
}
],
"abstract": "We study star formation histories (SFHs) of 500 dwarf galaxies (stellar mass M\u2217=10\u2075\u221210\u2079 M_\u2299\u2060) from FIRE-2 cosmological zoom-in simulations. We compare dwarfs around individual Milky Way (MW)-mass galaxies, dwarfs in Local Group (LG)-like environments, and true field (i.e. isolated) dwarf galaxies. We reproduce observed trends wherein higher mass dwarfs quench later (if at all), regardless of environment. We also identify differences between the environments, both in terms of 'satellite versus central' and 'LG versus individual MW versus isolated dwarf central.' Around the individual MW-mass hosts, we recover the result expected from environmental quenching: central galaxies in the 'near field' have more extended SFHs than their satellite counterparts, with the former more closely resemble isolated (true field) dwarfs (though near-field centrals are still somewhat earlier forming). However, this difference is muted in the LG-like environments, where both near-field centrals and satellites have similar SFHs, which resemble satellites of single MW-mass hosts. This distinction is strongest for M* = 10\u2076\u201310\u2077M\u2299 but exists at other masses. Our results suggest that the paired halo nature of the LG may regulate star formation in dwarf galaxies even beyond the virial radii of the MW and Andromeda. Caution is needed when comparing zoom-in simulations targeting isolated dwarf galaxies against observed dwarf galaxies in the LG.",
"doi": "10.1093/mnras/stz2507",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-11",
"series_number": "4",
"volume": "489",
"issue": "4",
"pages": "4574-4588"
},
{
"id": "authors:g0g55-w2442",
"collection": "authors",
"collection_id": "g0g55-w2442",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105628264",
"type": "article",
"title": "A Stable Finite-Volume Method for Scalar-Field Dark Matter",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We describe and test a family of new numerical methods to solve the Schr\u00f6dinger equation in self-gravitating systems, e.g. Bose\u2013Einstein condensates or 'fuzzy'/ultra-light scalar field dark matter. The methods are finite-volume Godunov schemes with stable, higher order accurate gradient estimation, based on a generalization of recent mesh-free finite-mass Godunov methods. They couple easily to particle-based N-body gravity solvers (with or without other fluids, e.g. baryons), are numerically stable, and computationally efficient. Different sub-methods allow for manifest conservation of mass, momentum, and energy. We consider a variety of test problems and demonstrate that these can accurately recover solutions and remain stable even in noisy, poorly resolved systems, with dramatically reduced noise compared to some other proposed implementations (though certain types of discontinuities remain challenging). This is non-trivial because the 'quantum pressure' is neither isotropic nor positive definite and depends on higher order gradients of the density field. We implement and test the method in the code GIZMO.",
"doi": "10.1093/mnras/stz1922",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-10",
"series_number": "2",
"volume": "489",
"issue": "2",
"pages": "2367-2376"
},
{
"id": "authors:vccrt-s0384",
"collection": "authors",
"collection_id": "vccrt-s0384",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191025-092112560",
"type": "article",
"title": "Non-linear evolution of instabilities between dust and sound waves",
"author": [
{
"family_name": "Moseley",
"given_name": "Eric R.",
"clpid": "Moseley-E-R"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-J"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We study the non-linear evolution of the acoustic 'resonant drag instability' (RDI) using numerical simulations. The acoustic RDI is excited in a dust\u2013gas mixture when dust grains stream through gas, interacting with sound waves to cause a linear instability. We study this process in a periodic box by accelerating neutral dust with an external driving force. The instability grows as predicted by linear theory, eventually breaking into turbulence and saturating. As in linear theory, the non-linear behaviour is characterized by three regimes \u2013 high, intermediate, and low wavenumbers \u2013 the boundary between which is determined by the dust\u2013gas coupling strength and the dust-to-gas mass ratio. The high and intermediate wavenumber regimes behave similarly to one another, with large dust-to-gas ratio fluctuations while the gas remains largely incompressible. The saturated state is highly anisotropic: dust is concentrated in filaments, jets, or plumes along the direction of acceleration, with turbulent vortex-like structures rapidly forming and dissipating in the perpendicular directions. The low-wavenumber regime exhibits large fluctuations in gas and dust density, but the dust and gas remain more strongly coupled in coherent 'fronts' perpendicular to the acceleration. These behaviours are qualitatively different from those of dust 'passively' driven by external hydrodynamic turbulence, with no back-reaction force from dust on to gas. The virulent nature of these instabilities has interesting implications for dust-driven winds in a variety of astrophysical systems, including around cool stars, in dusty torii around active-galactic-nuclei, and in and around giant molecular clouds.",
"doi": "10.1093/mnras/stz2128",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-10",
"series_number": "1",
"volume": "489",
"issue": "1",
"pages": "325-338"
},
{
"id": "authors:hyy9f-gh889",
"collection": "authors",
"collection_id": "hyy9f-gh889",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190726-085800598",
"type": "article",
"title": "On the dust temperatures of high redshift galaxies",
"author": [
{
"family_name": "Liang",
"given_name": "Lichen",
"orcid": "0000-0001-9422-0095",
"clpid": "Liang-Lichen"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Scoville",
"given_name": "Nick Z.",
"orcid": "0000-0002-0438-3323",
"clpid": "Scoville-N-Z"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Schreiber",
"given_name": "Corentin",
"clpid": "Schreiber-C"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
}
],
"abstract": "Dust temperature is an important property of the interstellar medium (ISM) of galaxies. It is required when converting (sub)millimetre broad-band flux to total infrared luminosity (L_(IR)), and hence star formation rate, in high-redshift galaxies. However, different definitions of dust temperatures have been used in the literature, leading to different physical interpretations of how ISM conditions change with, e.g. redshift and star formation rate. In this paper, we analyse the dust temperatures of massive (\u2060M_(star) > 10\u00b9\u2070M\u2299\u2060) z = 2\u20136 galaxies with the help of high-resolution cosmological simulations from the Feedback in Realistic Environments (FIRE) project. At z \u223c 2, our simulations successfully predict dust temperatures in good agreement with observations. We find that dust temperatures based on the peak emission wavelength increase with redshift, in line with the higher star formation activity at higher redshift, and are strongly correlated with the specific star formation rate. In contrast, the mass-weighted dust temperature, which is required to accurately estimate the total dust mass, does not strongly evolve with redshift over z = 2\u20136 at fixed IR luminosity but is tightly correlated with LIR at fixed z\u2060. We also analyse an 'equivalent' dust temperature for converting (sub)millimetre flux density to total IR luminosity, and provide a fitting formula as a function of redshift and dust-to-metal ratio. We find that galaxies of higher equivalent (or higher peak) dust temperature ('warmer dust') do not necessarily have higher mass-weighted temperatures. A 'two-phase' picture for interstellar dust can explain the different scaling relations of the various dust temperatures.",
"doi": "10.1093/mnras/stz2134",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-10",
"series_number": "1",
"volume": "489",
"issue": "1",
"pages": "1397-1422"
},
{
"id": "authors:rfjfx-d4453",
"collection": "authors",
"collection_id": "rfjfx-d4453",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105621305",
"type": "article",
"title": "Under the Firelight: Stellar Tracers of the Local Dark Matter Velocity Distribution in the Milky Way",
"author": [
{
"family_name": "Necib",
"given_name": "Lina",
"orcid": "0000-0003-2806-1414",
"clpid": "Necib-L"
},
{
"family_name": "Lisanti",
"given_name": "Mariangela",
"clpid": "Lisanti-M"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Sanderson",
"given_name": "Robyn",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-R-E"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "The Gaia era opens new possibilities for discovering the remnants of disrupted satellite galaxies in the solar neighborhood. If the population of local accreted stars is correlated with the dark matter sourced by the same mergers, one can then map the dark matter distribution directly. Using two cosmological zoom-in hydrodynamic simulations of Milky-Way-mass galaxies from the Latte suite of the FIRE-2 simulations, we find a strong correlation between the velocity distribution of stars and dark matter at the solar circle that were accreted from luminous satellites. This correspondence holds for dark matter that is either relaxed or in a kinematic substructure called debris flow, and is consistent between two simulated hosts with different merger histories. The correspondence is more problematic for streams because of possible spatial offsets between the dark matter and stars. We demonstrate how to reconstruct the dark matter velocity distribution from the observed properties of the accreted stellar population by properly accounting for the ratio of stars to dark matter contributed by individual mergers. This procedure does not account for the dark matter that originates from nonluminous satellites, which may constitute a nontrivial fraction of the local contribution. After validating this method using the FIRE-2 simulations, we apply it to the Milky Way and use it to recover the dark matter velocity distribution associated with the recently discovered stellar debris field in the solar neighborhood. Based on results from Gaia, we estimate that 42^(+26)_(-22)% of the local dark matter that is accreted from luminous mergers is in debris flow.",
"doi": "10.3847/1538-4357/ab3afc",
"issn": "1538-4357",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2019-09-20",
"series_number": "1",
"volume": "883",
"issue": "1",
"pages": "Art. No. 27"
},
{
"id": "authors:6wghm-yfq76",
"collection": "authors",
"collection_id": "6wghm-yfq76",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105641212",
"type": "article",
"title": "The Impact of Enhanced Halo Resolution on the Simulated Circumgalactic Medium",
"author": [
{
"family_name": "Hummels",
"given_name": "Cameron B.",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron-B"
},
{
"family_name": "Smith",
"given_name": "Britton D.",
"orcid": "0000-0002-6804-630X",
"clpid": "Smith-Britton-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "O'Shea",
"given_name": "Brian W.",
"clpid": "O'Shea-Brian-W"
},
{
"family_name": "Silvia",
"given_name": "Devin W.",
"orcid": "0000-0002-4109-9313",
"clpid": "Silvia-Devin-W"
},
{
"family_name": "Werk",
"given_name": "Jessica K.",
"orcid": "0000-0002-0355-0134",
"clpid": "Werk-Jessica-K"
},
{
"family_name": "Lehner",
"given_name": "Nicolas",
"orcid": "0000-0001-9158-0829",
"clpid": "Lehner-Nicolas"
},
{
"family_name": "Wise",
"given_name": "John H.",
"orcid": "0000-0003-1173-8847",
"clpid": "Wise-John-H"
},
{
"family_name": "Collins",
"given_name": "David C.",
"clpid": "Collins-David-C"
},
{
"family_name": "Butsky",
"given_name": "Iryna S.",
"orcid": "0000-0003-1257-5007",
"clpid": "Butsky-Iryna-S"
}
],
"abstract": "Traditional cosmological hydrodynamics simulations fail to spatially resolve the circumgalactic medium (CGM), the reservoir of tenuous gas surrounding a galaxy and extending to its virial radius. We introduce the technique of Enhanced Halo Resolution (EHR), enabling more realistic physical modeling of the simulated CGM by consistently forcing gas refinement to smaller scales throughout the virial halo of a simulated galaxy. We investigate the effects of EHR in the tempest simulations, a suite of enzo-based cosmological zoom simulations following the evolution of an L* galaxy, resolving spatial scales of 500 comoving pc out to 100 comoving kpc in galactocentric radius. Among its many effects, EHR (1) changes the thermal balance of the CGM, increasing its cool gas content and decreasing its warm/hot gas content; (2) preserves cool gas structures for longer periods; and (3) enables these cool clouds to exist at progressively smaller size scales. Observationally, this results in a boost in \"low ions\" like H i and a drop in \"high ions\" like O vi throughout the CGM. These effects of EHR do not converge in the tempest simulations, but extrapolating these trends suggests that the CGM is actually a mist consisting of ubiquitous, small, long-lived, cool clouds suspended in a medium at the halo virial temperature. We find that EHR produces the above effects by (1) better sampling the distribution of CGM phases, enabling runaway cooling in the dense, cool tail of the phase distribution; and (2) preventing cool gas clouds from artificially mixing with the ambient hot halo and evaporating.",
"doi": "10.3847/1538-4357/ab378f",
"issn": "1538-4357",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2019-09-10",
"series_number": "2",
"volume": "882",
"issue": "2",
"pages": "Art. No. 156"
},
{
"id": "authors:q01a8-ntj13",
"collection": "authors",
"collection_id": "q01a8-ntj13",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105541773",
"type": "article",
"title": "The radial acceleration relation is a natural consequence of the baryonic Tully-Fisher relation",
"author": [
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-C"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Dor\u00e9",
"given_name": "Olivier",
"orcid": "0000-0001-7432-2932",
"clpid": "Dor\u00e9-O"
}
],
"abstract": "Galaxies covering several orders of magnitude in stellar mass and a variety of Hubble types have been shown to follow the radial acceleration relation (RAR), a relationship between g_(obs), the observed circular acceleration of the galaxy, and g_(bar), the acceleration due to the total baryonic mass of the galaxy. For accelerations above 10^(10) m s^(-2), g_(obs), traces g_(bar), asymptoting to the 1:1 line. Below this scale, there is a break in the relation such that g_(obs) ~ g_(bar)^(1/2). We show that the RAR slope, scatter, and the acceleration scale are all natural consequences of the well-known baryonic Tully\u2013Fisher relation (BTFR). We further demonstrate that galaxies with a variety of baryonic and dark matter (DM) profiles and a wide range of dark halo and galaxy properties (well beyond those expected in Cold Dark Matter (CDM) theory) lie on the RAR if we simply require that their rotation curves satisfy the BTFR. We explore conditions needed to break this degeneracy: subkiloparsec resolved rotation curves inside of cored DM-dominated profiles and/or outside \u226b 100 kpc could lie on BTFR but deviate in the RAR, providing new constraints on DM.",
"doi": "10.3847/1538-4357/ab311b",
"issn": "1538-4357",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2019-09-01",
"series_number": "1",
"volume": "882",
"issue": "1",
"pages": "Art. No. 46"
},
{
"id": "authors:p5d4h-ykb65",
"collection": "authors",
"collection_id": "p5d4h-ykb65",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190911-150204286",
"type": "article",
"title": "The elephant in the room: the importance of the details of massive star formation in molecular clouds",
"author": [
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-M-Y"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Most simulations of galaxies and massive giant molecular clouds (GMCs) cannot explicitly resolve the formation (or predict the main-sequence masses) of individual stars. So they must use some prescription for the amount of feedback from an assumed population of massive stars (e.g. sampling the initial mass function, IMF). We perform a methods study of simulations of a star-forming GMC with stellar feedback from UV radiation, varying only the prescription for determining the luminosity of each stellar mass element formed (according to different IMF sampling schemes). We show that different prescriptions can lead to widely varying (factor of \u223c3) star formation efficiencies (on GMC scales) even though the average mass-to-light ratios agree. Discreteness of sources is important: radiative feedback from fewer, more-luminous sources has a greater effect for a given total luminosity. These differences can dominate over other, more widely recognized differences between similar literature GMC-scale studies (e.g. numerical methods, cloud initial conditions, presence of magnetic fields). Moreover the differences in these methods are not purely numerical: some make different implicit assumptions about the nature of massive star formation, and this remains deeply uncertain in star formation theory.",
"doi": "10.1093/mnras/stz1820",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-09",
"series_number": "2",
"volume": "488",
"issue": "2",
"pages": "2970-2975"
},
{
"id": "authors:0fb7n-2xd32",
"collection": "authors",
"collection_id": "0fb7n-2xd32",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105603989",
"type": "article",
"title": "On The Nature of Variations in the Measured Star Formation Efficiency of Molecular Clouds",
"author": [
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-M-Y"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Lee",
"given_name": "Eve J.",
"orcid": "0000-0002-1228-9820",
"clpid": "Lee-Eve-J"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Johnson",
"given_name": "L. Clifton",
"clpid": "Johnson-L-C"
}
],
"abstract": "Measurements of the star formation efficiency (SFE) of giant molecular clouds (GMCs) in the Milky Way generally show a large scatter, which could be intrinsic or observational. We use magnetohydrodynamic simulations of GMCs (including feedback) to forward-model the relationship between the true GMC SFE and observational proxies. We show that individual GMCs trace broad ranges of observed SFE throughout collapse, star formation, and disruption. Low measured SFEs (\u2060\u226a1 per cent\u2060) are 'real' but correspond to early stages; the true 'per-freefall' SFE where most stars actually form can be much larger. Very high (\u2060\u226b10 per cent\u2060) values are often artificially enhanced by rapid gas dispersal. Simulations including stellar feedback reproduce observed GMC-scale SFEs, but simulations without feedback produce 20\u00d7 larger SFEs. Radiative feedback dominates among mechanisms simulated. An anticorrelation of SFE with cloud mass is shown to be an observational artefact. We also explore individual dense 'clumps' within GMCs and show that (with feedback) their bulk properties agree well with observations. Predicted SFEs within the dense clumps are \u223c2\u00d7 larger than observed, possibly indicating physics other than feedback from massive (main-sequence) stars is needed to regulate their collapse.",
"doi": "10.1093/mnras/stz1758",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-09",
"series_number": "2",
"volume": "488",
"issue": "2",
"pages": "1501-1518"
},
{
"id": "authors:jae0p-3ma90",
"collection": "authors",
"collection_id": "jae0p-3ma90",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190912-080110123",
"type": "article",
"title": "Predictions for the spatial distribution of the dust continuum emission in 1 < z < 5 star-forming galaxies",
"author": [
{
"family_name": "Cochrane",
"given_name": "R. K.",
"orcid": "0000-0001-8855-6107",
"clpid": "Cochrane-R-K"
},
{
"family_name": "Hayward",
"given_name": "C. C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "D.",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-D"
},
{
"family_name": "Lotz",
"given_name": "J.",
"orcid": "0000-0003-3130-5643",
"clpid": "Lotz-J-M"
},
{
"family_name": "Parsotan",
"given_name": "T.",
"clpid": "Parsotan-T"
},
{
"family_name": "Ma",
"given_name": "X.",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Kere\u0161",
"given_name": "D.",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Feldmann",
"given_name": "R.",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "C. A.",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Hopkins",
"given_name": "P. F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We present the first detailed study of the spatially resolved dust continuum emission of simulated galaxies at 1 < z < 5. We run the radiative transfer code SKIRT on a sample of submillimetre-bright galaxies drawn from the Feedback In Realistic Environments (FIRE) project. These simulated galaxies reach Milky Way masses by z = 2. Our modelling provides predictions for the full rest-frame far-ultraviolet-to-far-infrared spectral energy distributions of these simulated galaxies, as well as 25-pc resolution maps of their emission across the wavelength spectrum. The derived morphologies are notably different in different wavebands, with the same galaxy often appearing clumpy and extended in the far-ultraviolet yet an ordered spiral at far-infrared wavelengths. The observed-frame 870-\u03bcm\u2009half-light radii of our FIRE-2 galaxies are \u223c0.5\u22124kpc\u2060, consistent with existing ALMA observations of galaxies with similarly high redshifts and stellar masses. In both simulated and observed galaxies, the dust continuum emission is generally more compact than the cold gas and the dust mass, but more extended than the stellar component. The most extreme cases of compact dust emission seem to be driven by particularly compact recent star formation, which generates steep dust temperature gradients. Our results confirm that the spatial extent of the dust continuum emission is sensitive to both the dust mass and star formation rate distributions.",
"doi": "10.1093/mnras/stz1736",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-09",
"series_number": "2",
"volume": "488",
"issue": "2",
"pages": "1779-1789"
},
{
"id": "authors:wxm51-cep22",
"collection": "authors",
"collection_id": "wxm51-cep22",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105655182",
"type": "article",
"title": "Cosmic ray feedback in the FIRE simulations: constraining cosmic ray propagation with GeV gamma ray emission",
"author": [
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Kere\u0161",
"given_name": "D.",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Hopkins",
"given_name": "P. F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "E.",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Su",
"given_name": "K.-Y.",
"orcid": "0000-0003-1598-0083",
"clpid": "Su-Kung-Yi"
},
{
"family_name": "Hayward",
"given_name": "C. C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "C.-A.",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
}
],
"abstract": "We present the implementation and the first results of cosmic ray (CR) feedback in the Feedback In Realistic Environments (FIRE) simulations. We investigate CR feedback in non-cosmological simulations of dwarf, sub-L\u22c6 starburst, and L\u22c6 galaxies with different propagation models, including advection, isotropic, and anisotropic diffusion, and streaming along field lines with different transport coefficients. We simulate CR diffusion and streaming simultaneously in galaxies with high resolution, using a two-moment method. We forward-model and compare to observations of \u03b3-ray emission from nearby and starburst galaxies. We reproduce the \u03b3-ray observations of dwarf and L\u22c6 galaxies with constant isotropic diffusion coefficient \u03ba\u223c3\u00d710^(29)cm^2s^(-1)\u2060. Advection-only and streaming-only models produce order of magnitude too large \u03b3-ray luminosities in dwarf and L\u22c6 galaxies. We show that in models that match the \u03b3-ray observations, most CRs escape low-gas-density galaxies (e.g. dwarfs) before significant collisional losses, while starburst galaxies are CR proton calorimeters. While adiabatic losses can be significant, they occur only after CRs escape galaxies, so they are only of secondary importance for \u03b3-ray emissivities. Models where CRs are 'trapped' in the star-forming disc have lower star formation efficiency, but these models are ruled out by \u03b3-ray observations. For models with constant \u03ba that match the \u03b3-ray observations, CRs form extended haloes with scale heights of several kpc to several tens of kpc.",
"doi": "10.1093/mnras/stz1895",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-09",
"series_number": "3",
"volume": "488",
"issue": "3",
"pages": "3716-3744"
},
{
"id": "authors:6grzv-58n55",
"collection": "authors",
"collection_id": "6grzv-58n55",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105631812",
"type": "article",
"title": "The Origins of the Circumgalactic Medium in the FIRE Simulations",
"author": [
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Stern",
"given_name": "Jonathan",
"orcid": "0000-0002-7541-9565",
"clpid": "Stern-Jonathan"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Hummels",
"given_name": "Cameron",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-Cameron-B"
},
{
"family_name": "Esmerian",
"given_name": "Clarke",
"orcid": "0000-0003-4575-4845",
"clpid": "Esmerian-Clarke-J"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Murray",
"given_name": "Norman",
"orcid": "0000-0002-8659-3729",
"clpid": "Murray-Norman-W"
}
],
"abstract": "We use a particle tracking analysis to study the origins of the circumgalactic medium (CGM), separating it into (1) accretion from the intergalactic medium (IGM), (2) wind from the central galaxy, and (3) gas ejected from other galaxies. Our sample consists of 21 FIRE-2 simulations, spanning the halo mass range Mh \u223c 10^(10)\u201310^(12) M\u2299, and we focus on z = 0.25 and z = 2. Owing to strong stellar feedback, only \u223cL\u22c6 haloes retain a baryon mass \u227350 per cent of their cosmic budget. Metals are more efficiently retained by haloes, with a retention fraction \u227350 per cent\u2060. Across all masses and redshifts analysed \u227360 per cent of the CGM mass originates as IGM accretion (some of which is associated with infalling haloes). Overall, the second most important contribution is wind from the central galaxy, though gas ejected or stripped from satellites can contribute a comparable mass in \u223cL\u22c6 haloes. Gas can persist in the CGM for billions of years, resulting in well mixed-halo gas. Sightlines through the CGM are therefore likely to intersect gas of multiple origins. For low-redshift \u223cL\u22c6 haloes, cool gas (T < 10^(4.7) K) is distributed on average preferentially along the galaxy plane, however with strong halo-to-halo variability. The metallicity of IGM accretion is systematically lower than the metallicity of winds (typically by \u22731 dex), although CGM and IGM metallicities depend significantly on the treatment of subgrid metal diffusion. Our results highlight the multiple physical mechanisms that contribute to the CGM and will inform observational efforts to develop a cohesive picture.",
"doi": "10.1093/mnras/stz1773",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-09",
"series_number": "1",
"volume": "488",
"issue": "1",
"pages": "1248-1272"
},
{
"id": "authors:ww60x-d0y81",
"collection": "authors",
"collection_id": "ww60x-d0y81",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190725-125944777",
"type": "article",
"title": "Dust attenuation, dust emission, and dust temperature in galaxies at z \u2265 5: a view from the FIRE-2 simulations",
"author": [
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Casey",
"given_name": "Caitlin M.",
"orcid": "0000-0002-0930-6466",
"clpid": "Casey-C-M"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Liang",
"given_name": "Lichen",
"orcid": "0000-0001-9422-0095",
"clpid": "Liang-Lichen"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "We present a suite of 34 high-resolution cosmological zoom-in simulations consisting of thousands of haloes up to M_(halo) \u223c 10^(12) M_\u2299 (\u2060M_\u2217 \u223c 10^(10.5) M_\u2299\u2060) at z \u2265 5 from the Feedback in Realistic Environments project. We post-process our simulations with a three-dimensional Monte Carlo dust radiative transfer code to study dust attenuation, dust emission, and dust temperature within these simulated z \u2265 5 galaxies. Our sample forms a tight correlation between infrared excess (IRX \u2261 F_(IR)/F_(UV)) and ultraviolet (UV)-continuum slope (\u03b2UV), despite the patchy, clumpy dust geometry shown in our simulations. We find that the IRX\u2013\u03b2UV relation is mainly determined by the shape of the attenuation law and is independent of its normalization (set by the dust-to-gas ratio). The bolometric IR luminosity (L_(IR)) correlates with the intrinsic UV luminosity and the star formation rate (SFR) averaged over the past 10\u2009Myr. We predict that at a given L_(IR), the peak wavelength of the dust spectral energy distributions for z \u2265 5 galaxies is smaller by a factor of 2 (due to higher dust temperatures on average) than at z = 0. The higher dust temperatures are driven by higher specific SFRs and SFR surface densities with increasing redshift. We derive the galaxy UV luminosity functions (UVLFs) at z = 5\u201310 from our simulations and confirm that a heavy attenuation is required to reproduce the observed bright-end UVLFs. We also predict the IR luminosity functions (IRLFs) and UV luminosity densities at z = 5\u201310. We discuss the implications of our results on current and future observations probing dust attenuation and emission in z \u2265 5 galaxies.",
"doi": "10.1093/mnras/stz1324",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-08",
"series_number": "2",
"volume": "487",
"issue": "2",
"pages": "1844-1864"
},
{
"id": "authors:av895-mcy25",
"collection": "authors",
"collection_id": "av895-mcy25",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105607525",
"type": "article",
"title": "The failure of stellar feedback, magnetic fields, conduction, and morphological quenching in maintaining red galaxies",
"author": [
{
"family_name": "Su",
"given_name": "Kung-Yi",
"orcid": "0000-0003-1598-0083",
"clpid": "Su-Kung-Yi"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-M-E"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Robles",
"given_name": "Victor H.",
"orcid": "0000-0002-9497-9963",
"clpid": "Robles-V-H"
}
],
"abstract": "The quenching 'maintenance' and related 'cooling flow' problems are important in galaxies from Milky Way mass through clusters. We investigate this in haloes with masses \u223c10^(12)\u221210^(14)M\u2299\u2060, using non-cosmological high-resolution hydrodynamic simulations with the FIRE-2 (Feedback In Realistic Environments) stellar feedback model. We specifically focus on physics present without AGN, and show that various proposed 'non-AGN' solution mechanisms in the literature, including Type Ia supernovae, shocked AGB winds, other forms of stellar feedback (e.g. cosmic rays), magnetic fields, Spitzer\u2013Braginskii conduction, or 'morphological quenching' do not halt or substantially reduce cooling flows nor maintain 'quenched' galaxies in this mass range. We show that stellar feedback (including cosmic rays from SNe) alters the balance of cold/warm gas and the rate at which the cooled gas within the galaxy turns into stars, but not the net baryonic inflow. If anything, outflowing metals and dense gas promote additional cooling. Conduction is important only in the most massive haloes, as expected, but even at \u223c10^(14)M\u2299 reduces inflow only by a factor \u223c2 (owing to saturation effects and anisotropic suppression). Changing the morphology of the galaxies only slightly alters their Toomre-Q parameter, and has no effect on cooling (as expected), so has essentially no effect on cooling flows or maintaining quenching. This all supports the idea that additional physics, e.g. AGN feedback, must be important in massive galaxies.",
"doi": "10.1093/mnras/stz1494",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-08",
"series_number": "3",
"volume": "487",
"issue": "3",
"pages": "4393-4408"
},
{
"id": "authors:7f8kp-j5v44",
"collection": "authors",
"collection_id": "7f8kp-j5v44",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105552297",
"type": "article",
"title": "The Local Group on FIRE: Dwarf galaxy populations across a suite of hydrodynamic simulations",
"author": [
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Lamberts",
"given_name": "Astrid",
"orcid": "0000-0001-8740-0127",
"clpid": "Lamberts-Astrid"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Sanderson",
"given_name": "Robyn",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-Robyn-E"
}
],
"abstract": "We present a new set of high-resolution hydrodynamic cosmological zoom-in simulations that apply the Feedback In Realistic Environments physics to both Local Group (LG)-like and isolated Milky Way (MW)-like volumes (10 host systems in total with a baryonic particle mass \u22433500\u22127000M\u2060). We study the stellar mass functions, circular velocity or mass profiles, and velocity dispersions of the dwarf galaxy populations. The simulations reproduce the stellar mass function and central densities of MW satellite dwarfs for M\u2217\u226510^(5.5) M\u2299 and predict the existence of \u223c3 unidentified galaxies with M\u2217\u223c10^5M\u2299 within 300 kpc of the MW. Overall, we find no evidence for the classical missing satellites or too-big-to-fail (TBTF) problems for satellite galaxies in our sample. Among the satellites, TBTF is resolved primarily by subhalo disruption and overall mass-loss; central density profiles of subhaloes are of secondary importance. For non-satellite galaxies, our LG-like simulations predict as many as \u223c10 as-of-yet unseen galaxies at distances 0.3\u22121Mpc from both hosts, with M\u2217\u224310^(5\u22126) M\u2299 (in haloes with V_(max) \u223c 20 km\u2009s^(\u22121)), albeit with large halo-to-halo variance. None of our simulations produces a compact, baryon-dominated, high-density dwarf elliptical-type galaxy (with V_(circ) \u2273 35 km\u2009s^(\u22121) at r < 1kpc), of which six may appear in the LG (but none in the MW). It may therefore remain a challenge to reproduce the full diversity of the dwarf population, including both the highest and lowest density systems.",
"doi": "10.1093/mnras/stz1317",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-07",
"series_number": "1",
"volume": "487",
"issue": "1",
"pages": "1380-1399"
},
{
"id": "authors:0094d-xbe30",
"collection": "authors",
"collection_id": "0094d-xbe30",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105614389",
"type": "article",
"title": "A Simple Non-equilibrium Feedback Model for Galaxy-Scale Star Formation: Delayed Feedback and SFR Scatter",
"author": [
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-M-E"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We explore a class of simple non-equilibrium star formation models within the framework of a feedback-regulated model of the ISM, applicable to kiloparsec-scale resolved star formation relations (e.g. Kennicutt\u2013Schmidt). Combining a Toomre-Q-dependent local star formation efficiency per free-fall time with a model for delayed feedback, we are able to match the normalization and scatter of resolved star formation scaling relations. In particular, this simple model suggests that large (\u223cdex) variations in star formation rates (SFRs) on kiloparsec scales may be due to the fact that supernova feedback is not instantaneous following star formation. The scatter in SFRs at constant gas surface density in a galaxy then depends on the properties of feedback and when we observe its star-forming regions at various points throughout their collapse/star formation 'cycles'. This has the following important observational consequences: (1) the scatter and normalization of the Kennicutt\u2013Schmidt relation are relatively insensitive to the local (small-scale) star formation efficiency; (2) but gas depletion times and velocity dispersions are; (3) the scatter in and normalization of the Kennicutt\u2013Schmidt relation is a sensitive probe of the feedback time-scale and strength; (4) even in a model where \u02dcQ_(gas) deterministically dictates star formation locally, time evolution, variation in local conditions (e.g. gas fractions and dynamical times), and variations between galaxies can destroy much of the observable correlation between SFR and \u02dcQ_(gas) in resolved galaxy surveys. Additionally, this model exhibits large scatter in SFRs at low gas surface densities, in agreement with observations of flat outer H\u2009I disc velocity dispersion profiles.",
"doi": "10.1093/mnras/stz1156",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-07",
"series_number": "4",
"volume": "486",
"issue": "4",
"pages": "4724-4737"
},
{
"id": "authors:7dhcp-hp003",
"collection": "authors",
"collection_id": "7dhcp-hp003",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190725-125944080",
"type": "article",
"title": "Is it possible to reconcile extragalactic IMF variations with a universal Milky Way IMF?",
"author": [
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Graus",
"given_name": "Andrew S.",
"clpid": "Graus-A-S"
}
],
"abstract": "One of the most robust observations of the stellar initial mass function (IMF) is its near-universality in the Milky Way and neighbouring galaxies. But recent observations of early-type galaxies can be interpreted to imply a 'bottom-heavy' IMF, while others of ultrafaint dwarfs could imply a 'top-heavy' IMF. This would impose powerful constraints on star formation models. We explore what sort of 'cloud-scale' IMF models could possibly satisfy these constraints. We utilize simulated galaxies that reproduce (broadly) the observed galaxy properties, while they also provide the detailed star formation history and properties of each progenitor star-forming cloud. We then consider generic models where the characteristic mass of the IMF is some arbitrary power-law function of progenitor cloud properties, along with well-known literature IMF models which scale with Jeans mass, 'turbulent Bonnor\u2013Ebert mass', temperature, the opacity limit, metallicity, or the 'protostellar heating mass'. We show that no IMF models currently in the literature \u2013 nor any model where the turnover mass is an arbitrary power-law function of a combination of cloud temperature/density/size/metallicity/velocity dispersion/magnetic field \u2013 can reproduce the claimed IMF variation in ellipticals or dwarfs without severely violating observational constraints in the Milky Way. Specifically, they predict too much variation in the 'extreme' environments of the Galaxy compared to that observed. Either the IMF varies in a more complicated manner, or alternative interpretations of the extragalactic observations must be explored.",
"doi": "10.1093/mnras/stz736",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-06",
"series_number": "4",
"volume": "485",
"issue": "4",
"pages": "4852-4862"
},
{
"id": "authors:6x4bz-35q24",
"collection": "authors",
"collection_id": "6x4bz-35q24",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105548856",
"type": "article",
"title": "Formation, vertex deviation and age of the Milky Way's bulge: input from a cosmological simulation with a late-forming bar",
"author": [
{
"family_name": "Debattista",
"given_name": "Victor P.",
"orcid": "0000-0001-7902-0116",
"clpid": "Debattista-Victor-P"
},
{
"family_name": "Gonzalez",
"given_name": "Oscar A.",
"orcid": "0000-0003-2478-6020",
"clpid": "Gonzalez-Oscar-A"
},
{
"family_name": "Sanderson",
"given_name": "Robyn E.",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-Robyn-E"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We present the late-time evolution of m12m, a cosmological simulation of a Milky Way-like galaxy from the FIRE project. The simulation forms a bar after redshift z = 0.2. We show that the evolution of the model exhibits behaviours typical of kinematic fractionation, with a bar weaker in older populations, an X-shape traced by the younger, metal-rich populations, and a prominent X-shape in the edge-on mean metallicity map. Because of the late formation of the bar in m12m, stars forming after 10Gyr (z = 0.34) significantly contaminate the bulge, at a level higher than is observed at high latitudes in the Milky Way, implying that its bar cannot have formed as late as in m12m. We also study the model's vertex deviation of the velocity ellipsoid as a function of stellar metallicity and age in the equivalent of Baade's Window. The formation of the bar leads to a non-zero vertex deviation. We find that metal-rich stars have a large vertex deviation (\u223c40\u00b0), which becomes negligible for metal-poor stars, a trend also found in the Milky Way, despite not matching in detail. We demonstrate that the vertex deviation also varies with stellar age and is large for stars as old as 9Gyr\u2060, while 13Gyr old stars have negligible vertex deviation. When we exclude stars that have been accreted, the vertex deviation is not significantly changed, demonstrating that the observed variation of vertex deviation with metallicity is not necessarily due to an accreted population.",
"doi": "10.1093/mnras/stz746",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-06",
"series_number": "4",
"volume": "485",
"issue": "4",
"pages": "5073-5085"
},
{
"id": "authors:7j58a-x3098",
"collection": "authors",
"collection_id": "7j58a-x3098",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-072411270",
"type": "article",
"title": "Interacting galaxies on FIRE-2: the connection between enhanced star formation and interstellar gas content",
"author": [
{
"family_name": "Moreno",
"given_name": "Jorge",
"clpid": "Moreno-J"
},
{
"family_name": "Torrey",
"given_name": "Paul",
"orcid": "0000-0002-5653-0786",
"clpid": "Torrey-P"
},
{
"family_name": "Ellison",
"given_name": "Sara L.",
"orcid": "0000-0002-1768-1899",
"clpid": "Ellison-S-L"
},
{
"family_name": "Patton",
"given_name": "David R.",
"clpid": "Patton-D-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Bueno",
"given_name": "Michael",
"clpid": "Bueno-M"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-D"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Bluck",
"given_name": "Asa F. L.",
"clpid": "Bluck-A-F-L"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
}
],
"abstract": "We present a comprehensive suite of high-resolution (parsec-scale), idealized (non-cosmological) galaxy merger simulations (24 runs, stellar mass ratio \u223c2.5:1) to investigate the connection between interaction-induced star formation and the evolution of the interstellar medium (ISM) in various temperature\u2013density regimes. We use the GIZMO code and the second version of the 'Feedback in Realistic Environments' model (FIRE-2), which captures the multiphase structure of the ISM. Our simulations are designed to represent galaxy mergers in the local Universe. In this work, we focus on the 'galaxy-pair period' between first and second pericentric passage. We split the ISM into four regimes: hot, warm, cool, and cold-dense, motivated by the hot, ionized, atomic and molecular gas phases observed in real galaxies. We find that, on average, interactions enhance the star formation rate of the pair (\u2060\u223c30 per cent, merger-suite sample average) and elevate their cold-dense gas content (\u2060\u223c18 per cent\u2060). This is accompanied by a decrease in warm gas (\u2060\u223c11 per cent), a negligible change in cool gas (\u2060\u223c4 per cent increase), and a substantial increase in hot gas (\u2060\u223c400 per cent\u2060). The amount of cold-dense gas with densities above 1000 cm^(\u22123) (the cold ultra-dense regime) is elevated significantly (\u2060\u223c240 per cent\u2060), but only accounts for \u223c0.15 per cent (on average) of the cold-dense gas budget.",
"doi": "10.1093/mnras/stz417",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-05",
"series_number": "1",
"volume": "485",
"issue": "1",
"pages": "1320-1338"
},
{
"id": "authors:tj32q-hg182",
"collection": "authors",
"collection_id": "tj32q-hg182",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105617834",
"type": "article",
"title": "Non-linear evolution of the resonant drag instability in magnetized gas",
"author": [
{
"family_name": "Seligman",
"given_name": "Darryl",
"clpid": "Seligman-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-J"
}
],
"abstract": "We investigate, for the first time, the non-linear evolution of the magnetized 'resonant drag instabilities' (RDIs). We explore magnetohydrodynamic simulations of gas mixed with (uniform) dust grains subject to Lorentz and drag forces, using the GIZMO code. The magnetized RDIs exhibit fundamentally different behaviour than purely acoustic RDIs. The dust organizes into coherent structures and the system exhibits strong dust\u2013gas separation. In the linear and early non-linear regime, the growth rates agree with linear theory and the dust self-organizes into 2D planes or 'sheets.' Eventually the gas develops fully non-linear, saturated Alfv\u00e9nic, and compressible fast-mode turbulence, which fills the underdense regions with a small amount of dust, and drives a dynamo that saturates at equipartition of kinetic and magnetic energy. The dust density fluctuations exhibit significant non-Gaussianity, and the power spectrum is strongly weighted towards the largest (box scale) modes. The saturation level can be understood via quasi-linear theory, as the forcing and energy input via the instabilities become comparable to saturated tension forces and dissipation in turbulence. The magnetized simulation presented here is just one case; it is likely that the magnetic RDIs can take many forms in different parts of parameter space.",
"doi": "10.1093/mnras/stz666",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-05",
"series_number": "3",
"volume": "485",
"issue": "3",
"pages": "3991-3998"
},
{
"id": "authors:ns93f-g8m71",
"collection": "authors",
"collection_id": "ns93f-g8m71",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190207-163502830",
"type": "article",
"title": "The robustness of cosmological hydrodynamic simulation predictions to changes in numerics and cooling physics",
"author": [
{
"family_name": "Huang",
"given_name": "Shuiyao",
"orcid": "0000-0002-6571-0738",
"clpid": "Huang-Shuiyao"
},
{
"family_name": "Katz",
"given_name": "Neal",
"orcid": "0000-0002-3097-5381",
"clpid": "Katz-Neal"
},
{
"family_name": "Dav\u00e9",
"given_name": "Romeel",
"orcid": "0000-0003-2842-9434",
"clpid": "Dav\u00e9-Romeel"
},
{
"family_name": "Fardal",
"given_name": "Mark",
"clpid": "Fardal-M-A"
},
{
"family_name": "Kollmeier",
"given_name": "Juna",
"orcid": "0000-0001-9852-1610",
"clpid": "Kollmeier-J-A"
},
{
"family_name": "Oppenheimer",
"given_name": "Benjamin D.",
"orcid": "0000-0003-4754-6863",
"clpid": "Oppenheimer-Benjamin-D"
},
{
"family_name": "Peeples",
"given_name": "Molly S.",
"orcid": "0000-0003-1455-8788",
"clpid": "Peeples-M-S"
},
{
"family_name": "Roberts",
"given_name": "Shawn",
"clpid": "Roberts-S"
},
{
"family_name": "Weinberg",
"given_name": "David H.",
"clpid": "Weinberg-D-H"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Thompson",
"given_name": "Robert",
"clpid": "Thompson-R"
}
],
"abstract": "We test and improve the numerical schemes in our smoothed particle hydrodynamics (SPH) code for cosmological simulations, including the pressure\u2013entropy formulation (PESPH), a time-dependent artificial viscosity, a refined time-step criterion, and metal-line cooling that accounts for photoionization in the presence of a recently refined Haardt & Madau model of the ionizing background. The PESPH algorithm effectively removes the artificial surface tension present in the traditional SPH formulation, and in our test simulations, it produces better qualitative agreement with mesh-code results for Kelvin\u2013Helmholtz instability and cold cloud disruption. Using a set of cosmological simulations, we examine many of the quantities we have studied in previous work. Results for galaxy stellar and H\u2009I mass functions, star formation histories, galaxy scaling relations, and statistics of the Ly\u03b1 forest are robust to the changes in numerics and microphysics. As in our previous simulations, cold gas accretion dominates the growth of high-redshift galaxies and of low-mass galaxies at low redshift, and recycling of winds dominates the growth of massive galaxies at low redshift. However, the PESPH simulation removes spurious cold clumps seen in our earlier simulations, and the accretion rate of hot gas increases by up to an order of magnitude at some redshifts. The new numerical model also influences the distribution of metals among gas phases, leading to considerable differences in the statistics of some metal absorption lines, most notably Ne\u2009VIII.",
"doi": "10.1093/mnras/stz057",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-04-01",
"series_number": "2",
"volume": "484",
"issue": "2",
"pages": "2021-2046"
},
{
"id": "authors:ycz3v-25977",
"collection": "authors",
"collection_id": "ycz3v-25977",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105658617",
"type": "article",
"title": "Local simulations of MRI turbulence with meshless methods",
"author": [
{
"family_name": "Deng",
"given_name": "Hongping",
"orcid": "0000-0001-6858-1006",
"clpid": "Deng-Hongping"
},
{
"family_name": "Mayer",
"given_name": "Lucio",
"clpid": "Mayer-L"
},
{
"family_name": "Latter",
"given_name": "Henrik",
"clpid": "Latter-H"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Bai",
"given_name": "Xue-Ning",
"orcid": "0000-0001-6906-9549",
"clpid": "Bai-Xue-Ning"
}
],
"abstract": "The magneto-rotational instability (MRI) is one of the most important processes in sufficiently ionized astrophysical disks. Grid-based simulations, especially those using the local shearing box approximation, provide a powerful tool to study the nonlinear turbulence the MRI produces. On the other hand, meshless methods have been widely used in cosmology, galactic dynamics, and planet formation, but have not been fully deployed on the MRI problem. We present local unstratified and vertically stratified MRI simulations with two meshless MHD schemes: a recent implementation of smoothed-particle magnetohydrodynamics (SPH MHD), and a meshless finite-mass (MFM) MHD scheme with constrained gradient divergence cleaning, as implemented in the GIZMO code. Concerning variants of the SPH hydro force formulation, we consider both the \"vanilla\" SPH and the PSPH variant included in GIZMO. We find, as expected, that the numerical noise inherent in these schemes significantly affects turbulence. Furthermore, a high-order kernel, free of the pairing instability, is necessary. Both schemes adequately simulate MRI turbulence in unstratified shearing boxes with net vertical flux. The turbulence, however, dies out in zero-net-flux unstratified boxes, probably due to excessive numerical dissipation. In zero-net-flux vertically stratified simulations, MFM can reproduce the MRI dynamo and its characteristic butterfly diagram for several tens of orbits before ultimately decaying. In contrast, extremely strong toroidal fields, as opposed to sustained turbulence, develop in equivalent simulations using SPH MHD. The latter unphysical state is likely caused by a combination of excessive artificial viscosity, numerical resistivity, and the relatively large residual errors in the divergence of the magnetic field.",
"doi": "10.3847/1538-4365/ab0957",
"issn": "1538-4365",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Supplement Series",
"publication_date": "2019-04",
"series_number": "2",
"volume": "241",
"issue": "2",
"pages": "Art. No. 26"
},
{
"id": "authors:g4399-md255",
"collection": "authors",
"collection_id": "g4399-md255",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-112124271",
"type": "article",
"title": "The physics of Lyman\u00a0\u03b1 escape from high-redshift galaxies",
"author": [
{
"family_name": "Smith",
"given_name": "Aaron",
"orcid": "0000-0002-2838-9033",
"clpid": "Smith-Aaron"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Bromm",
"given_name": "Volker",
"clpid": "Bromm-V"
},
{
"family_name": "Finkelstein",
"given_name": "Steven L.",
"orcid": "0000-0001-8519-1130",
"clpid": "Finkelstein-S-L"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "Lyman \u03b1 (Ly\u03b1) photons from ionizing sources and cooling radiation undergo a complex resonant scattering process that generates unique spectral signatures in high-redshift galaxies. We present a detailed Ly\u03b1 radiative transfer study of a cosmological zoom-in simulation from the Feedback In Realistic Environments (FIRE) project. We focus on the time, spatial, and angular properties of the Ly\u03b1 emission over a redshift range of z = 5\u20137, after escaping the galaxy and being transmitted through the intergalactic medium (IGM). Over this epoch, our target galaxy has an average stellar mass of M\u22c6 \u2248 5\u00d710^8M\u2299 .We find that many of the interesting features of the Ly\u03b1 line can be understood in terms of the galaxy's star formation history. The time variability, spatial morphology, and anisotropy of Ly\u03b1 properties are consistent with current observations. For example, the rest-frame equivalent width has an EW_(Ly\u03b1,0) > 20\u02daA duty cycle of 62 per cent with a non-negligible number of sightlines with >100\u02daA\u2060, associated with outflowing regions of a starburst with greater coincident UV continuum absorption, as these conditions generate redder, narrower (or single-peaked) line profiles. The lowest equivalent widths correspond to cosmological filaments, which have little impact on UV continuum photons but efficiently trap Ly\u03b1 and produce bluer, broader lines with less transmission through the IGM. We also show that in dense self-shielding, low-metallicity filaments and satellites, Ly\u03b1 radiation pressure can be dynamically important. Finally, despite a significant reduction in surface brightness with increasing redshift, Ly\u03b1 detections and spectroscopy of high-z galaxies with the upcoming James Webb Space Telescope is feasible.",
"doi": "10.1093/mnras/sty3483",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-03-21",
"series_number": "1",
"volume": "484",
"issue": "1",
"pages": "39-59"
},
{
"id": "authors:pd6ve-dwh42",
"collection": "authors",
"collection_id": "pd6ve-dwh42",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190115-143918003",
"type": "article",
"title": "The maximum stellar surface density due to the failure of stellar feedback",
"author": [
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"clpid": "Grudi\u0107-M-Y"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N"
}
],
"abstract": "A maximum stellar surface density \u03a3_(max) \u223c 3\u00d710^5M\u2299 pc^(\u22122) is observed across all classes of dense stellar systems (e.g. star clusters, galactic nuclei, etc.), spanning \u223c8 orders of magnitude in mass. It has been proposed that this characteristic scale is set by some dynamical feedback mechanism preventing collapse beyond a certain surface density. However, simple analytic models and detailed simulations of star formation moderated by feedback from massive stars argue that feedback becomes less efficient at higher surface densities (with the star formation efficiency increasing as \u223c\u03a3/\u03a3_(crit)). We therefore propose an alternative model wherein stellar feedback becomes ineffective at moderating star formation above some \u03a3_(crit), so the supply of star-forming gas is rapidly converted to stars before the system can contract to higher surface density. We show that such a model \u2013 with \u03a3_(crit) taken directly from the theory \u2013 naturally predicts the observed \u03a3_(max). We find \u03a3_(max) \u223c 100\u03a3_(crit) because the gas consumption time is longer than the global free-fall time even when feedback is ineffective. Moreover, the predicted \u03a3_(max) is robust to spatial scale and metallicity, and is preserved even if multiple episodes of star formation/gas inflow occur. In this context, the observed \u03a3_(max) directly tells us where feedback fails.",
"doi": "10.1093/mnras/sty3386",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-03-11",
"series_number": "4",
"volume": "483",
"issue": "4",
"pages": "5548-5553"
},
{
"id": "authors:wcfmv-ehq60",
"collection": "authors",
"collection_id": "wcfmv-ehq60",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-135711599",
"type": "article",
"title": "Dynamic localized turbulent diffusion and its impact on the galactic ecosystem",
"author": [
{
"family_name": "Rennehan",
"given_name": "Douglas",
"orcid": "0000-0002-1619-8555",
"clpid": "Rennehan-D"
},
{
"family_name": "Babul",
"given_name": "Arif",
"orcid": "0000-0003-1746-9529",
"clpid": "Babul-A"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Dav\u00e9",
"given_name": "Romeel",
"clpid": "Dav\u00e9-R"
},
{
"family_name": "Moa",
"given_name": "Belaid",
"clpid": "Moa-B"
}
],
"abstract": "Modelling the turbulent diffusion of thermal energy, momentum, and metals is required in all galaxy evolution simulations due to the ubiquity of turbulence in galactic environments. The most commonly employed diffusion model, the Smagorinsky model, is known to be overdiffusive due to its strong dependence on the fluid velocity shear. We present a method for dynamically calculating a more accurate, locally appropriate, turbulent diffusivity: the dynamic localized Smagorinsky model. We investigate a set of standard astrophysically relevant hydrodynamical tests, and demonstrate that the dynamic model curbs overdiffusion in non-turbulent shear flows and improves the density contrast in our driven turbulence experiments. In galactic discs, we find that the dynamic model maintains the stability of the disc by preventing excessive angular momentum transport, and increases the metal-mixing time-scale in the interstellar medium. In both our isolated Milky Way-like galaxies and cosmological simulations, we find that the interstellar and circumgalactic media are particularly sensitive to the treatment of turbulent diffusion. We also examined the global gas enrichment fractions in our cosmological simulations, to gauge the potential effect on the formation sites and population statistics of Population III stars and supermassive black holes, since they are theorized to be sensitive to the metallicity of the gas out of which they form. The dynamic model is, however, not for galaxy evolution studies only. It can be applied to all astrophysical hydrodynamics simulations, including those modelling stellar interiors, planetary formation, and star formation.",
"doi": "10.1093/mnras/sty3376",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-03-01",
"series_number": "3",
"volume": "483",
"issue": "3",
"pages": "3810-3831"
},
{
"id": "authors:6wvhv-zv633",
"collection": "authors",
"collection_id": "6wvhv-zv633",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190411-140903892",
"type": "article",
"title": "Warm FIRE: simulating galaxy formation with resonant sterile neutrino dark matter",
"author": [
{
"family_name": "Bozek",
"given_name": "Brandon",
"clpid": "Bozek-B"
},
{
"family_name": "Fitts",
"given_name": "Alex",
"orcid": "0000-0002-8928-6011",
"clpid": "Fitts-A"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Abazajian",
"given_name": "Kevork",
"orcid": "0000-0001-9919-6362",
"clpid": "Abazajian-K"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-J-S"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We study the impact of a warm dark matter (WDM) cosmology on dwarf galaxy formation through a suite of cosmological hydrodynamical zoom-in simulations of M_(halo) \u2248 10^(10) M\u2299 dark matter haloes as part of the Feedback in Realistic Environments (FIRE) project. A main focus of this paper is to evaluate the combined effects of dark matter physics and stellar feedback on the well-known small-scale issues found in cold dark matter (CDM) models. We find that the z = 0 stellar mass of a galaxy is strongly correlated with the central density of its host dark matter halo at the time of formation, z_f, in both CDM and WDM models. WDM haloes follow the same M\u22c6(\u2060z = 0)\u2013V_(max)(\u2060z_f) relation as in CDM, but they form later, are less centrally dense, and therefore contain galaxies that are less massive than their CDM counterparts. As a result, the impact of baryonic effects on the central gravitational potential is typically diminished relative to CDM. However, the combination of delayed formation in WDM and energy input from stellar feedback results in dark matter profiles with lower overall densities. The WDM galaxies studied here have a wider diversity of star formation histories (SFHs) than the same systems simulated in CDM, and the two lowest M\u22c6 WDM galaxies form all of their stars at late times. The discovery of young ultrafaint dwarf galaxies with no ancient star formation \u2013 which do not exist in our CDM simulations \u2013 would therefore provide evidence in support of WDM.",
"doi": "10.1093/mnras/sty3300",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-03",
"series_number": "3",
"volume": "483",
"issue": "3",
"pages": "4086-4099"
},
{
"id": "authors:t3t8q-w6681",
"collection": "authors",
"collection_id": "t3t8q-w6681",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190411-130929118",
"type": "article",
"title": "Numerical problems in coupling photon momentum (radiation pressure) to gas",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-M-Y"
}
],
"abstract": "Radiation pressure (RP; or photon momentum absorbed by gas) is important in a tremendous range of astrophysical systems. But we show the usual method for assigning absorbed photon momentum to gas in numerical radiation-hydrodynamics simulations (integrating over cell volumes or evaluating at cell centres) can severely underestimate the RP force in the immediate vicinity around unresolved (point/discrete) sources (and subsequently underestimate its effects on bulk gas properties), unless photon mean free paths are highly resolved in the fluid grid. The existence of this error is independent of the numerical radiation transfer (RT) method (even in exact ray-tracing/Monte Carlo methods), because it depends on how the RT solution is interpolated back onto fluid elements. Brute-force convergence (resolving mean free paths) is impossible in many cases (especially where UV/ionizing photons are involved). Instead, we show a 'face-integrated' method \u2013 integrating and applying the momentum fluxes at interfaces between fluid elements \u2013 better approximates the correct solution at all resolution levels. The 'fix' is simple and we provide example implementations for ray-tracing, Monte Carlo, and moments RT methods in both grid and mesh-free fluid schemes. We consider an example of star formation in a molecular cloud with UV/ionizing RP. At state-of-the-art resolution, cell-integrated methods underestimate the net effects of RP by an order of magnitude, leading (incorrectly) to the conclusion that RP is unimportant, while face-integrated methods predict strong self-regulation of star formation and cloud destruction via RP.",
"doi": "10.1093/mnras/sty3089",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-03",
"series_number": "3",
"volume": "483",
"issue": "3",
"pages": "4187-4196"
},
{
"id": "authors:647wy-93p22",
"collection": "authors",
"collection_id": "647wy-93p22",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-095615659",
"type": "article",
"title": "Effects of Gas on Formation and Evolution of Stellar Bars and Nuclear Rings in Disk Galaxies",
"author": [
{
"family_name": "Seo",
"given_name": "Woo-Young",
"orcid": "0000-0002-5444-3320",
"clpid": "Seo-Woo-Young"
},
{
"family_name": "Kim",
"given_name": "Woong-Tae",
"orcid": "0000-0003-4625-229X",
"clpid": "Kim-Woong-Tae"
},
{
"family_name": "Kwak",
"given_name": "SungWon",
"orcid": "0000-0003-0957-6201",
"clpid": "Kwak-SungWon"
},
{
"family_name": "Hsieh",
"given_name": "Pei-Ying",
"orcid": "0000-0001-9155-3978",
"clpid": "Hsieh-Pei-Ying"
},
{
"family_name": "Han",
"given_name": "Cheongho",
"orcid": "0000-0002-2641-9964",
"clpid": "Han-Cheongho"
},
{
"family_name": "Hopkins",
"given_name": "Phil F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We run self-consistent simulations of Milky Way-sized, isolated disk galaxies to study the formation and evolution of a stellar bar as well as a nuclear ring in the presence of gas. We consider two sets of models with cold or warm disks that differ in the radial velocity dispersions, and vary the gas fraction f_(gas) by fixing the total disk mass. A bar forms earlier and more strongly in the cold disks with larger f_(gas), while gas progressively delays the bar formation in the warm disks. The bar formation enhances a central mass concentration, which in turn causes the bar to decay temporarily, after which it regrows in size and strength, eventually becoming stronger in models with smaller f_(gas). Although all bars rotate fast in the beginning, they rapidly turn to slow rotators. In our models, only the gas-free, warm disk undergoes rapid buckling instability, while other disks thicken more gradually via vertical heating. The gas driven inward by the bar potential readily forms a star-forming nuclear ring. The ring is very small when it first forms and grows in size over time. The ring star formation rate is episodic and bursty due to feedback, and is well correlated with the mass inflow rate to the ring. Some expanding shells produced by star formation feedback are sheared out in the bar regions and collide with dust lanes to appear as filamentary interbar spurs. The bars and nuclear rings formed in our simulations have properties similar to those in the Milky Way.",
"doi": "10.3847/1538-4357/aafc5f",
"issn": "1538-4357",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2019-02-10",
"series_number": "1",
"volume": "872",
"issue": "1",
"pages": "Art. No. 5"
},
{
"id": "authors:whz19-g8707",
"collection": "authors",
"collection_id": "whz19-g8707",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190415-103759070",
"type": "article",
"title": "What drives the evolution of gas kinematics in star-forming galaxies?",
"author": [
{
"family_name": "Hung",
"given_name": "Chao-Ling",
"orcid": "0000-0002-6879-3639",
"clpid": "Hung-Chao-Ling"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Yuan",
"given_name": "Tiantian",
"clpid": "Yuan-Tiantian"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
}
],
"abstract": "One important result from recent large integral field spectrograph (IFS) surveys is that the intrinsic velocity dispersion of galaxies traced by star-forming gas increases with redshift. Massive, rotation-dominated discs are already in place at z \u223c 2, but they are dynamically hotter than spiral galaxies in the local Universe. Although several plausible mechanisms for this elevated velocity dispersion (e.g. star formation feedback, elevated gas supply, or more frequent galaxy interactions) have been proposed, the fundamental driver of the velocity dispersion enhancement at high redshift remains unclear. We investigate the origin of this kinematic evolution using a suite of cosmological simulations from the FIRE (Feedback In Realistic Environments) project. Although IFS surveys generally cover a wider range of stellar masses than in these simulations, the simulated galaxies show trends between intrinsic velocity dispersion (\u03c3_(intr)), SFR, and z in agreement with observations. In both observations and simulations, galaxies on the star-forming main sequence have median \u03c3_(intr) values that increase from z \u223c 0 to z \u223c 1\u20131.5, but this increasing trend is less evident at higher redshift. In the FIRE simulations, \u03c3_(intr) can vary significantly on time-scales of \u2272100. These variations closely mirror the time evolution of the SFR and gas inflow rate (\u2060M_(gas)\u2060). By cross-correlating pairs of \u03c3_(intr), M_(gas)\u2060, and SFR, we show that increased gas inflow leads to subsequent enhanced star formation, and enhancements in \u03c3_(intr) tend to temporally coincide with increases in M_(gas) and SFR.",
"doi": "10.1093/mnras/sty2970",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-02",
"series_number": "4",
"volume": "482",
"issue": "4",
"pages": "5125-5137"
},
{
"id": "authors:xprwx-9kj45",
"collection": "authors",
"collection_id": "xprwx-9kj45",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181205-145100415",
"type": "article",
"title": "The origin of the diverse morphologies and kinematics of Milky Way-mass galaxies in the FIRE-2 simulations",
"author": [
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Sanderson",
"given_name": "Robyn E.",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-Robyn-E"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "van\u00a0de\u00a0Voort",
"given_name": "Freeke",
"orcid": "0000-0002-6301-638X",
"clpid": "van-de-Voort-Freeke"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
}
],
"abstract": "We use hydrodynamic cosmological zoom-in simulations from the Feedback in Realistic Environments project to explore the morphologies and kinematics of 15 Milky Way (MW)-mass galaxies. Our sample ranges from compact, bulge-dominated systems with 90 per\u2009cent of their stellar mass within 2.5\u2009kpc to well-ordered discs that reach \u227315\u2009kpc. The gas in our galaxies always forms a thin, rotation-supported disc at z = 0, with sizes primarily determined by the gas mass. For stars, we quantify kinematics and morphology both via the fraction of stars on disc-like orbits and with the radial extent of the stellar disc. In this mass range, stellar morphology and kinematics are poorly correlated with the properties of the halo available from dark matter-only simulations (halo merger history, spin, or formation time). They more strongly correlate with the gaseous histories of the galaxies: those that maintain a high gas mass in the disc after z \u223c 1 develop well-ordered stellar discs. The best predictor of morphology we identify is the spin of the gas in the halo at the time the galaxy formed 1/2 of its stars (i.e. the gas that builds the galaxy). High-z mergers, before a hot halo emerges, produce some of the most massive bulges in the sample (from compact discs in gas-rich mergers), while later-forming bulges typically originate from internal processes, as satellites are stripped of gas before the galaxies merge. Moreover, most stars in z = 0 MW-mass galaxies (even z = 0 bulge stars) form in a disc: \u227360--90 per cent of stars begin their lives rotationally supported.",
"doi": "10.1093/mnras/sty2513",
"pmcid": "PMC6310044",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-12-11",
"series_number": "3",
"volume": "481",
"issue": "3",
"pages": "4133-4157"
},
{
"id": "authors:923pd-r5b97",
"collection": "authors",
"collection_id": "923pd-r5b97",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180109-173930013",
"type": "article",
"title": "Reconciling observed and simulated stellar halo masses",
"author": [
{
"family_name": "Sanderson",
"given_name": "Robyn E.",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-R-E"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Chan",
"given_name": "Tsang Keung",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Escala",
"given_name": "Ivanna",
"orcid": "0000-0002-9933-9551",
"clpid": "Escala-I"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
}
],
"abstract": "We use cosmological hydrodynamical simulations of Milky Way\u2013mass galaxies from the FIRE project to evaluate various strategies for estimating the mass of a galaxy's stellar halo from deep, integrated-light images. We find good agreement with integrated-light observations if we mimic observational methods to measure the mass of the stellar halo by selecting regions of an image via projected radius relative to the disk scale length or by their surface density in stellar mass. However, these observational methods systematically underestimate the accreted stellar component, defined in our (and most) simulations as the mass of stars formed outside of the host galaxy, by up to a factor of 10, since the accreted component is centrally concentrated and therefore substantially obscured by the galactic disk. Furthermore, these observational methods introduce spurious dependencies of the estimated accreted stellar component on the stellar mass and size of galaxies that can obscure the trends in accreted stellar mass predicted by cosmological simulations, since we find that in our simulations, the size and shape of the central galaxy are not strongly correlated with the assembly history of the accreted stellar halo. This effect persists whether galaxies are viewed edge-on or face-on. We show that metallicity or color information may provide a way to more cleanly delineate in observations the regions dominated by accreted stars. Absent additional data, we caution that estimates of the mass of the accreted stellar component from single-band images alone should be taken as lower limits.",
"doi": "10.3847/1538-4357/aaeb33",
"issn": "1538-4357",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2018-12-10",
"series_number": "1",
"volume": "869",
"issue": "1",
"pages": "Art. No. 12"
},
{
"id": "authors:009xb-a0835",
"collection": "authors",
"collection_id": "009xb-a0835",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181129-111459057",
"type": "article",
"title": "From the top down and back up again: star cluster structure from hierarchical star formation",
"author": [
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-Michael-Y"
},
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D\u00e1vid"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Lamberts",
"given_name": "Astrid",
"orcid": "0000-0001-8740-0127",
"clpid": "Lamberts-Astrid"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-Norman-W"
},
{
"family_name": "Schmitz",
"given_name": "Denise",
"orcid": "0000-0001-6297-9312",
"clpid": "Schmitz-Denise-M"
}
],
"abstract": "Young massive star clusters spanning \u223c10^4--10^8 M_\u2299 in mass have been observed to have similar surface brightness profiles. We show that recent hydrodynamical simulations of star cluster formation have also produced star clusters with this structure. We argue analytically that this type of mass distribution arises naturally in the relaxation from a hierarchically clustered distribution of stars into a monolithic star cluster through hierarchical merging. We show that initial profiles of finite maximum density will tend to produce successively shallower power-law profiles under hierarchical merging, owing to certain conservation constraints on the phase-space distribution. We perform N-body simulations of a pairwise merger of model star clusters and find that mergers readily produce the shallow surface brightness profiles observed in young massive clusters. Finally, we simulate the relaxation of a hierarchically clustered mass distribution constructed from an idealized fragmentation model. Assuming only power-law spatial and kinematic scaling relations, these numerical experiments are able to reproduce the surface density profiles of observed young massive star clusters. Thus, we bolster the physical motivation for the structure of young massive clusters within the paradigm of hierarchical star formation. This could have important implications for the structure and dynamics of nascent globular clusters.",
"doi": "10.1093/mnras/sty2303",
"pmcid": "PMC6296242",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-11-21",
"series_number": "1",
"volume": "481",
"issue": "1",
"pages": "688-702"
},
{
"id": "authors:nyj7y-vz027",
"collection": "authors",
"collection_id": "nyj7y-vz027",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181205-163501557",
"type": "article",
"title": "Discrete Effects in Stellar Feedback: Individual Supernovae, Hypernovae, and IMF Sampling in Dwarf Galaxies",
"author": [
{
"family_name": "Su",
"given_name": "Kung-Yi",
"orcid": "0000-0003-1598-0083",
"clpid": "Su-Kung-Yi"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Kasen",
"given_name": "Daniel",
"orcid": "0000-0002-5981-1022",
"clpid": "Kasen-D"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-M-E"
},
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-C"
}
],
"abstract": "Using high-resolution simulations from the FIRE-2 (Feedback In Realistic Environments) project, we study the effects of discreteness in stellar feedback processes on the evolution of galaxies and the properties of the interstellar medium (ISM). We specifically consider the discretization of supernovae (SNe), including hypernovae (HNe), and sampling the initial mass function (IMF). We study these processes in cosmological simulations of dwarf galaxies with z = 0 stellar masses M_\u2217\u223c10^4--3\u00d710^6 M_\u2299 (halo masses \u223c10^9--10^(10) M_\u2299\u2060). We show that the discrete nature of individual SNe (as opposed to a model in which their energy/momentum deposition is continuous overtime, similar to stellar winds) is crucial in generating a reasonable ISM structure and galactic winds and in regulating dwarf stellar masses. However, once SNe are discretized, accounting for the effects of IMF sampling on continuous mechanisms such as radiative feedback and stellar mass-loss (as opposed to adopting IMF-averaged rates) has weak effects on galaxy-scale properties. We also consider the effects of rare HNe events with energies \u223c10^(53) erg\u2060. The effects of HNe are similar to the effects of clustered explosions of SNe \u2013 which are already captured in our default simulation setup \u2013 and do not quench star formation (provided that the HNe do not dominate the total SNe energy budget), which suggests that HNe yield products should be observable in ultra-faint dwarfs today.",
"doi": "10.1093/mnras/sty1928",
"pmcid": "PMC6301068",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-10-21",
"series_number": "2",
"volume": "480",
"issue": "2",
"pages": "1666-1675"
},
{
"id": "authors:84jbc-6gk93",
"collection": "authors",
"collection_id": "84jbc-6gk93",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170713-154123249",
"type": "article",
"title": "The Resonant Drag Instability (RDI): Acoustic Modes",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-J"
}
],
"abstract": "Recently, Squire & Hopkins showed any coupled dust\u2013gas mixture is subject to a class of linear 'resonant drag instabilities' (RDI). These can drive large dust-to-gas ratio fluctuations even at arbitrarily small dust-to-gas mass ratios \u03bc. Here, we identify and study both resonant and new non-resonant instabilities, in the simple case where the gas satisfies neutral hydrodynamics and supports acoustic waves (\u03c9^2=c^2_sk^2). The gas and dust are coupled via an arbitrary drag law and subject to external accelerations (e.g. gravity, radiation pressure). If there is any dust drift velocity, the system is unstable. The instabilities exist for all dust-to-gas ratios \u03bc and their growth rates depend only weakly on \u03bc around resonance, as \u223c\u03bc^(1/3) or \u223c\u03bc^(1/2) (depending on wavenumber). The behaviour changes depending on whether the drift velocity is larger or smaller than the sound speed cs. In the supersonic regime, a 'resonant' instability appears with growth rate increasing without limit with wavenumber, even for vanishingly small \u03bc and values of the coupling strength (stopping time). In the subsonic regime, non-resonant instabilities always exist, but their growth rates no longer increase indefinitely towards small wavelengths. The dimensional scalings and qualitative behaviour of the instability do not depend sensitively on the drag law or equation of state of the gas. The instabilities directly drive exponentially growing dust-to-gas-ratio fluctuations, which can be large even when the modes are otherwise weak. We discuss physical implications for cool-star winds, AGN-driven winds and torii, and starburst winds: the instabilities alter the character of these outflows and could drive clumping and/or turbulence in the dust and gas.",
"doi": "10.1093/mnras/sty1982",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-10-21",
"series_number": "2",
"volume": "480",
"issue": "2",
"pages": "2813-2838"
},
{
"id": "authors:sf09p-kvm69",
"collection": "authors",
"collection_id": "sf09p-kvm69",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181205-163501316",
"type": "article",
"title": "Predicting the binary black hole population of the Milky Way with cosmological simulations",
"author": [
{
"family_name": "Lamberts",
"given_name": "A.",
"orcid": "0000-0001-8740-0127",
"clpid": "Lamberts-A"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "S.",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Hopkins",
"given_name": "P. F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "E.",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Bullock",
"given_name": "J. S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-J-S"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "C.-A.",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Wetzel",
"given_name": "A.",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Kere\u0161",
"given_name": "D.",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Drango",
"given_name": "K.",
"clpid": "Drango-K"
},
{
"family_name": "Sanderson",
"given_name": "R. E.",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-R-E"
}
],
"abstract": "Binary black holes are the primary endpoint of massive stars. Their properties provide a unique opportunity to constrain binary evolution, which remains poorly understood. We predict the main properties of binary black holes and their merger products in/around the Milky Way. We present the first combination of a high-resolution cosmological simulation of a Milky Way-mass galaxy with a binary population synthesis model in this context. The hydrodynamic simulation, taken from the FIRE project, provides a cosmologically realistic star formation history for the galaxy, its stellar halo, and satellites. During post-processing, we apply a metallicity-dependent evolutionary model to the star particles to produce individual binary black holes. We find that 7 \u00d7 10^5 binary black holes have merged in the model Milky Way, and 1.2 \u00d7 10^6 binaries are still present, with a mean mass of 28 M_\u2299\u2060. Because the black hole progenitors are strongly biased towards low-metallicity stars, half reside in the stellar halo and satellites and a third were formed outside the main galaxy. The numbers and mass distribution of the merged systems is broadly compatible with the LIGO/Virgo detections. Our simplified binary evolution models predict that LISA will detect more than 20 binary black holes, but that electromagnetic observations will be challenging. Our method will allow for constraints on the evolution of massive binaries based on comparisons between observations of compact objects and the predictions of varying binary evolution models. We provide online data of our star formation model and binary black hole distribution.",
"doi": "10.1093/mnras/sty2035",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-10-21",
"series_number": "2",
"volume": "480",
"issue": "2",
"pages": "2704-2718"
},
{
"id": "authors:pvv0t-1hs79",
"collection": "authors",
"collection_id": "pvv0t-1hs79",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180913-133203850",
"type": "article",
"title": "Isothermal Fragmentation: Is there a low-mass cut-off?",
"author": [
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"clpid": "Grudi\u0107-M-Y"
},
{
"family_name": "Krumholz",
"given_name": "Mark R.",
"orcid": "0000-0003-3893-854X",
"clpid": "Krumholz-M-R"
},
{
"family_name": "Federrath",
"given_name": "Christoph",
"clpid": "Federrath-C"
}
],
"abstract": "The evolution of self-gravitating clouds of isothermal gas forms the basis of many star formation theories. Therefore it is important to know under what conditions such a cloud will undergo monolithic collapse into a single, massive object, or will fragment into a spectrum of smaller ones. And if it fragments, do initial conditions (e.g. Jeans mass, sonic mass) influence the mass function of the fragments, as predicted by many theories of star formation? In this paper we show that the relevant parameter separating monolithic collapse from fragmentation is not the Mach number of the initial turbulence (as suspected by many), but the infall Mach number M_(infall) \u223c \u221aGM/(Rc^2_s ), equivalent to the number of Jeans masses in the initial cloud NJ. We also show that fragmenting clouds produce a power-law mass function with slopes close to the expected -2 (i.e. equal mass in all logarithmic mass intervals). However, the low-mass cut-off of this mass function is entirely numerical; the initial properties of the cloud have no effect on it. In other words, if M_(infall) \u226b 1, fragmentation proceeds without limit to masses much smaller than the initial Jeans mass.",
"doi": "10.1093/mnras/sty1847",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-10-11",
"series_number": "1",
"volume": "480",
"issue": "1",
"pages": "182-191"
},
{
"id": "authors:ahmtv-2c998",
"collection": "authors",
"collection_id": "ahmtv-2c998",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180723-104220389",
"type": "article",
"title": "FIRE-2 Simulations: Physics versus Numerics in Galaxy Formation",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Hummels",
"given_name": "Cameron",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-C-B"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Su",
"given_name": "Kung-Yi",
"orcid": "0000-0003-1598-0083",
"clpid": "Su-Kung-Yi"
},
{
"family_name": "Orr",
"given_name": "Matthew",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-M-E"
},
{
"family_name": "Schmitz",
"given_name": "Denise",
"orcid": "0000-0001-6297-9312",
"clpid": "Schmitz-D-M"
},
{
"family_name": "Escala",
"given_name": "Ivanna",
"orcid": "0000-0002-9933-9551",
"clpid": "Escala-I"
},
{
"family_name": "Sanderson",
"given_name": "Robyn",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-R-E"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-M-Y"
},
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-C"
}
],
"abstract": "The Feedback In Realistic Environments (FIRE) project explores feedback in cosmological galaxy formation simulations. Previous FIRE simulations used an identical source code (\"FIRE-1\") for consistency. Motivated by the development of more accurate numerics \u2013 including hydrodynamic solvers, gravitational softening, and supernova coupling algorithms \u2013 and exploration of new physics (e.g. magnetic fields), we introduce \"FIRE-2\", an updated numerical implementation of FIRE physics for the GIZMO code. We run a suite of simulations and compare against FIRE-1: overall, FIRE-2 improvements do not qualitatively change galaxy-scale properties. We pursue an extensive study of numerics versus physics. Details of the star-formation algorithm, cooling physics, and chemistry have weak effects, provided that we include metal-line cooling and star formation occurs at higher-than-mean densities. We present new resolution criteria for high-resolution galaxy simulations. Most galaxy-scale properties are robust to numerics we test, provided: (1) Toomre masses are resolved; (2) feedback coupling ensures conservation, and (3) individual supernovae are time-resolved. Stellar masses and profiles are most robust to resolution, followed by metal abundances and morphologies, followed by properties of winds and circum-galactic media (CGM). Central (\u223ckpc) mass concentrations in massive (>L*) galaxies are sensitive to numerics (via trapping/recycling of winds in hot halos). Multiple feedback mechanisms play key roles: supernovae regulate stellar masses/winds; stellar mass-loss fuels late star formation; radiative feedback suppresses accretion onto dwarfs and instantaneous star formation in disks. We provide all initial conditions and numerical algorithms used.",
"doi": "10.1093/mnras/sty1690",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-10-11",
"series_number": "1",
"volume": "480",
"issue": "1",
"pages": "800-863"
},
{
"id": "authors:q9v2k-jpz71",
"collection": "authors",
"collection_id": "q9v2k-jpz71",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180912-153417896",
"type": "article",
"title": "Where are the most ancient stars in the Milky Way?",
"author": [
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Bland-Hawthorn",
"given_name": "Joss",
"orcid": "0000-0001-7516-4016",
"clpid": "Bland-Hawthorn-Joss"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Weisz",
"given_name": "Daniel R.",
"orcid": "0000-0002-6442-6030",
"clpid": "Weisz-Daniel-R"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
}
],
"abstract": "The oldest stars in the Milky Way (MW) bear imprints of the Galaxy's early assembly history. We use FIRE cosmological zoom-in simulations of three MW-mass disc galaxies to study the spatial distribution, chemistry, and kinematics of the oldest surviving stars (z_(form) \u2273 5) in MW-like galaxies. We predict the oldest stars to be less centrally concentrated at z = 0 than stars formed at later times as a result of two processes. First, the majority of the oldest stars are not formed in situ but are accreted during hierarchical assembly. These ex situ stars are deposited on dispersion-supported, halo-like orbits but dominate over old stars formed in situ in the solar neighbourhood, and in some simulations, even in the galactic centre. Secondly, old stars formed in situ are driven outwards by bursty star formation and energetic feedback processes that create a time-varying gravitational potential at z \u2273 2, similar to the process that creates dark matter cores and expands stellar orbits in bursty dwarf galaxies. The total fraction of stars that are ancient is more than an order of magnitude higher for sight lines away from the bulge and inner halo than for inward-looking sight lines. Although the task of identifying specific stars as ancient remains challenging, we anticipate that million-star spectral surveys and photometric surveys targeting metal-poor stars already include hundreds of stars formed before z = 5. We predict most of these targets to have higher metallicity (-3 < [Fe/H] < -2) than the most extreme metal-poor stars.",
"doi": "10.1093/mnras/sty1864",
"pmcid": "PMC6301095",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-10-11",
"series_number": "1",
"volume": "480",
"issue": "1",
"pages": "652-668"
},
{
"id": "authors:27kq0-q7n45",
"collection": "authors",
"collection_id": "27kq0-q7n45",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180829-160558722",
"type": "article",
"title": "Ubiquitous instabilities of dust moving in magnetized gas",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-J"
}
],
"abstract": "Squire & Hopkins showed that coupled dust\u2013gas mixtures are generically subject to 'resonant drag instabilities' (RDIs), which drive violently growing fluctuations in both. But the role of magnetic fields and charged dust has not yet been studied. We therefore explore the RDI in gas that obeys ideal MHD and is coupled to dust via both Lorentz forces and drag, with an external acceleration (e.g. gravity, radiation) driving dust drift through gas. We show this is always unstable, at all wavelengths and non-zero values of dust-to-gas ratio, drift velocity, dust charge, 'stopping time' or drag coefficient (for any drag law), or field strength; moreover, growth rates depend only weakly (sub-linearly) on these parameters. Dust charge and magnetic fields do not suppress instabilities, but give rise to a large number of new instability 'families,' each with distinct behavior. The 'MHD-wave' (magnetosonic or Alfv\u00e9n) RDIs exhibit maximal growth along 'resonant' angles where the modes have a phase velocity matching the corresponding MHD wave, and growth rates increase without limit with wavenumber. The 'gyro' RDIs are driven by resonances between drift and Larmor frequencies, giving growth rates sharply peaked at specific wavelengths. Other instabilities include 'acoustic' and 'pressure-free' modes (previously studied), and a family akin to cosmic ray instabilities that appear when Lorentz forces are strong and dust streams super-Alfv\u00e9nically along field lines. We discuss astrophysical applications in the warm ISM, circum-galactic medium/inter-galactic medium (CGM/IGM), H II regions, SNe ejecta/remnants, Solar corona, cool-star winds, GMCs, and AGN.",
"doi": "10.1093/mnras/sty1604",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-10-01",
"series_number": "4",
"volume": "479",
"issue": "4",
"pages": "4681-4719"
},
{
"id": "authors:t85f3-ez468",
"collection": "authors",
"collection_id": "t85f3-ez468",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180829-152027447",
"type": "article",
"title": "No assembly required: mergers are mostly irrelevant for the growth of low-mass dwarf galaxies",
"author": [
{
"family_name": "Fitts",
"given_name": "Alex",
"orcid": "0000-0002-8928-6011",
"clpid": "Fitts-Alex"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Weisz",
"given_name": "Daniel R.",
"orcid": "0000-0002-6442-6030",
"clpid": "Weisz-Daniel-R"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-Coral-R"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
}
],
"abstract": "We investigate the merger histories of isolated dwarf galaxies based on a suite of 15 high-resolution cosmological zoom-in simulations, all with masses of M_(halo) \u2248 10^(10) M\u2299 (and M\u22c6\u223c10^5\u221210^7 M_\u2299) at z = 0, from the Feedback in Realistic Environments project. The stellar populations of these dwarf galaxies at z = 0 are formed essentially entirely 'in situ': over 90\npercent of the stellar mass is formed in the main progenitor in all but two cases, and all 15 of the galaxies have >70 percent of their stellar mass formed in situ. Virtually all galaxy mergers occur prior to z \u223c 3, meaning that accreted stellar populations are ancient. On average, our simulated dwarfs undergo five galaxy mergers in their lifetimes, with typical pre-merger galaxy mass ratios that are less than 1:10. This merger frequency is generally comparable to what has been found in dissipationless simulations when coupled with abundance matching. Two of the simulated dwarfs have a luminous satellite companion at z= 0. These ultra-faint dwarfs lie at or below current detectability thresholds but are intriguing targets for next-generation facilities. The small contribution of accreted stars makes it extremely difficult to discern the effects of mergers in the vast majority of dwarfs either photometrically or using resolved-star colour\u2013magnitude diagrams (CMDs). The important implication for near-field cosmology is that star formation histories (SFHs) of comparably massive galaxies derived from resolved CMDs should trace the build-up of stellar mass in one main system across cosmic time as opposed to reflecting the contributions of many individual SFHs of merged dwarfs.",
"doi": "10.1093/mnras/sty1488",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-09-01",
"series_number": "1",
"volume": "479",
"issue": "1",
"pages": "319-331"
},
{
"id": "authors:kchny-dym06",
"collection": "authors",
"collection_id": "kchny-dym06",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180626-143234175",
"type": "article",
"title": "What FIREs up star formation: the emergence of the Kennicutt\u2013Schmidt law from feedback",
"author": [
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-M-E"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
}
],
"abstract": "We present an analysis of the global and spatially resolved Kennicutt\u2013Schmidt (KS) star formation relation in the FIRE (Feedback In Realistic Environments) suite of cosmological simulations, including haloes with z = 0 masses ranging from 10^(10) to 10^(13) M_\u2299. We show that the KS relation emerges and is robustly maintained due to the effects of feedback on local scales regulating star-forming gas, independent of the particular small-scale star formation prescriptions employed. We demonstrate that the time-averaged KS relation is relatively independent of redshift and spatial averaging scale, and that the star formation rate surface density is weakly dependent on metallicity and inversely dependent on orbital dynamical time. At constant star formation rate surface density, the 'cold and dense' gas surface density (gas with T < 300 K and n > 10 cm^(\u22123), used as a proxy for the molecular gas surface density) of the simulated galaxies is \u223c0.5 dex less than observed at \u223ckpc scales. This discrepancy may arise from underestimates of the local column density at the particle-scale for the purposes of shielding in the simulations. Finally, we show that on scales larger than individual giant molecular clouds, the primary condition that determines whether star formation occurs is whether a patch of the galactic disc is thermally Toomre-unstable (not whether it is self-shielding): once a patch can no longer be thermally stabilized against fragmentation, it collapses, becomes self-shielding, cools, and forms stars, regardless of epoch or environment.",
"doi": "10.1093/mnras/sty1241",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-08-21",
"series_number": "3",
"volume": "478",
"issue": "3",
"pages": "3653-3673"
},
{
"id": "authors:0q03n-n9h16",
"collection": "authors",
"collection_id": "0q03n-n9h16",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180809-123958372",
"type": "article",
"title": "Simulating galaxies in the reionization era with FIRE-2: galaxy scaling relations, stellar mass functions, and luminosity functions",
"author": [
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "We present a suite of cosmological zoom-in simulations at z \u2265 5 from the Feedback In Realistic Environments project, spanning a halo mass range Mhalo \u223c 10^8\u201310^(12)\u2009M\u2299 at z = 5. We predict the stellar mass\u2013halo mass relation, stellar mass function, and luminosity function in several bands from z = 5 to 12. The median stellar mass\u2013halo mass relation does not evolve strongly at z = 5\u201312. The faint-end slope of the luminosity function steepens with increasing redshift, as inherited from the halo mass function at these redshifts. Below z \u223c 6, the stellar mass function and ultraviolet (UV) luminosity function slightly flatten below M* \u223c 10^(4.5)\u2009M\u2299 (fainter than M_(1500) \u223c \u221212), owing to the fact that star formation in low-mass haloes is suppressed by the ionizing background by the end of reionization. Such flattening does not appear at higher redshifts. We provide redshift-dependent fitting functions for the SFR\u2013M_(halo), SFR\u2013M*, and broad-band magnitude\u2013stellar mass relations. We derive the star formation rate density and stellar mass density at z = 5\u201312 and show that the contribution from very faint galaxies becomes more important at z > 8. Furthermore, we find that the decline in the z \u223c 6 UV luminosity function brighter than M_(1500) \u223c \u221220 is largely due to dust attenuation. Approximately 37\u2009per\u2009cent (54\u2009per\u2009cent) of the UV luminosity from galaxies brighter than M_(1500) = \u221213 (\u221217) is obscured by dust at z \u223c 6. Our results broadly agree with current data and can be tested by future observations.",
"doi": "10.1093/mnras/sty1024",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-08-01",
"series_number": "2",
"volume": "478",
"issue": "2",
"pages": "1694-1715"
},
{
"id": "authors:62g0j-x8744",
"collection": "authors",
"collection_id": "62g0j-x8744",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181205-163501202",
"type": "article",
"title": "Submillimetre flux as a probe of molecular ISM mass in high-z galaxies",
"author": [
{
"family_name": "Liang",
"given_name": "Lichen",
"orcid": "0000-0001-9422-0095",
"clpid": "Liang-Lichen"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Scoville",
"given_name": "Nick Z.",
"orcid": "0000-0002-0438-3323",
"clpid": "Scoville-N-Z"
}
],
"abstract": "Recent long-wavelength observations on the thermal dust continuum suggest that the Rayleigh\u2013Jeans tail can be used as a time-efficient quantitative probe of the dust and interstellar medium (ISM) mass in high-z galaxies. We use high-resolution cosmological simulations from the Feedback in Realistic Environment (FIRE) project to analyse the dust emission of M* \u2273 10^(10)\u2009M_\u2299 galaxies at z = 2\u20134. Our simulations (MASSIVEFIRE) explicitly include various forms of stellar feedback, and they produce the stellar masses and star formation rates of high-z galaxies in agreement with observations. Using radiative transfer modelling, we show that sub-millimetre (sub-mm) luminosity and molecular ISM mass are tightly correlated and that the overall normalization is in quantitative agreement with observations. Notably, sub-mm luminosity traces molecular ISM mass even during starburst episodes as dust mass and mass-weighted temperature evolve only moderately between z = 4 and z = 2, including during starbursts. Our finding supports the empirical approach of using broadband sub-mm flux as a proxy for molecular gas content in high-z galaxies. We thus expect single-band sub-mm observations with ALMA to dramatically increase the sample size of high-z galaxies with reliable ISM masses in the near future.",
"doi": "10.1093/mnrasl/sly071",
"issn": "1745-3925",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society: Letters",
"publication_date": "2018-07-21",
"series_number": "1",
"volume": "478",
"issue": "1",
"pages": "L83-L88"
},
{
"id": "authors:dxa4p-wxh94",
"collection": "authors",
"collection_id": "dxa4p-wxh94",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180517-101404866",
"type": "article",
"title": "The origin of ultra diffuse galaxies: stellar feedback and quenching",
"author": [
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Kere\u0161",
"given_name": "D.",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Wetzel",
"given_name": "A.",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Hopkins",
"given_name": "P. F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "C.-A.",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "El-Badry",
"given_name": "K.",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "S.",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "M.",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
}
],
"abstract": "We test if the cosmological zoom-in simulations of isolated galaxies from the FIRE project reproduce the properties of ultra diffuse galaxies (UDGs). We show that outflows that dynamically heat galactic stars, together with a passively aging stellar population after imposed quenching, naturally reproduce the observed population of red UDGs, without the need for high spin halos, or dynamical influence from their host cluster. We reproduce the range of surface brightness, radius and absolute magnitude of the observed red UDGs by quenching simulated galaxies at a range of different times. They represent a mostly uniform population of dark matter-dominated dwarf galaxies with M* \u223c 10^8\u2009M\u2299, low metallicity and a broad range of ages; the more massive the UDGs, the older they are. The most massive red UDG in our sample (M* \u223c 3 \u00d7 10^8M\u2299) requires quenching at z \u223c 3 when its halo reached M_h \u223c 10^(11)\u2009M\u2299. Our simulated UDGs form with normal stellar-to-halo ratios and match the central enclosed masses and the velocity dispersions of the observed UDGs. Enclosed masses remain largely fixed across a broad range of quenching times because the central regions of their dark matter halos complete their growth early. If our simulated dwarfs are not quenched, they evolve into bluer low-surface brightness galaxies with M/L similar to observed field dwarfs. While our simulation sample covers a limited range of formation histories and halo masses, we predict that UDG is a common, and perhaps even dominant, galaxy type around M* \u223c 10^8\u2009M\u2299, both in the field and in clusters.",
"doi": "10.1093/mnras/sty1153",
"pmcid": "PMC6295926",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-07-21",
"series_number": "1",
"volume": "478",
"issue": "1",
"pages": "906-925"
},
{
"id": "authors:6036w-kjc77",
"collection": "authors",
"collection_id": "6036w-kjc77",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180705-140116376",
"type": "article",
"title": "Resonant drag instabilities in protoplanetary discs: the streaming instability and new, faster growing instabilities",
"author": [
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-J"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We identify and study a number of new, rapidly growing instabilities of dust grains in protoplanetary discs, which may be important for planetesimal formation. The study is based on the recognition that dust\u2013gas mixtures are generically unstable to a resonant drag instability (RDI), whenever the gas, absent dust, supports undamped linear modes. We show that the 'streaming instability' is an RDI associated with epicyclic oscillations; this provides simple interpretations for its mechanisms and accurate analytic expressions for its growth rates and fastest growing wavelengths. We extend this analysis to more general dust streaming motions and other waves, including buoyancy and magnetohydrodynamic oscillations, finding various new instabilities. Most importantly, we identify the disc 'settling instability,' which occurs as dust settles vertically into the mid-plane of a rotating disc. For small grains, this instability grows many orders of magnitude faster than the standard streaming instability, with a growth rate that is independent of grain size. Growth time scales for realistic dust-to-gas ratios are comparable to the disc orbital period, and the characteristic wavelengths are more than an order of magnitude larger than the streaming instability (allowing the instability to concentrate larger masses). This suggests that in the process of settling, dust will band into rings then filaments or clumps, potentially seeding dust traps, high-metallicity regions that in turn seed the streaming instability, or even overdensities that coagulate or directly collapse to planetesimals.",
"doi": "10.1093/mnras/sty854",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-07-11",
"series_number": "4",
"volume": "477",
"issue": "4",
"pages": "5011-5040"
},
{
"id": "authors:6xwfk-sq433",
"collection": "authors",
"collection_id": "6xwfk-sq433",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180705-141511132",
"type": "article",
"title": "Universal scaling relations in scale-free structure formation",
"author": [
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"clpid": "Grudi\u0107-M-Y"
}
],
"abstract": "A large number of astronomical phenomena exhibit remarkably similar scaling relations. The most well-known of these is the mass distribution dN/dM \u221d M^(\u22122) which (to first order) describes stars, protostellar cores, clumps, giant molecular clouds, star clusters, and even dark matter haloes. In this paper we propose that this ubiquity is not a coincidence and that it is the generic result of scale-free structure formation where the different scales are uncorrelated. We show that all such systems produce a mass function proportional to M^(\u22122) and a column density distribution with a power-law tail of dA/dln\u2009\u03a3 \u221d \u03a3^(\u22121). In the case where structure formation is controlled by gravity the two-point correlation becomes \u03be2D \u221d R^(\u22121). Furthermore, structures formed by such processes (e.g. young star clusters, DM haloes) tend to a \u03c1 \u221d R^(\u22123) density profile. We compare these predictions with observations, analytical fragmentation cascade models, semi-analytical models of gravito-turbulent fragmentation, and detailed 'full physics' hydrodynamical simulations. We find that these power laws are good first-order descriptions in all cases.",
"doi": "10.1093/mnras/sty920",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-07-11",
"series_number": "4",
"volume": "477",
"issue": "4",
"pages": "5139-5149"
},
{
"id": "authors:9dhr6-9y972",
"collection": "authors",
"collection_id": "9dhr6-9y972",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180627-140420805",
"type": "article",
"title": "How to model supernovae in simulations of star and galaxy formation",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Murray",
"given_name": "Norman",
"orcid": "0000-0002-8659-3729",
"clpid": "Murray-Norman-W"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
},
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
}
],
"abstract": "We study the implementation of mechanical feedback from supernovae (SNe) and stellar mass loss in galaxy simulations, within the Feedback In Realistic Environments (FIRE) project. We present the FIRE-2 algorithm for coupling mechanical feedback, which can be applied to any hydrodynamics method (e.g. fixed-grid, moving-mesh, and mesh-less methods), and black hole as well as stellar feedback. This algorithm ensures manifest conservation of mass, energy, and momentum, and avoids imprinting 'preferred directions' on the ejecta. We show that it is critical to incorporate both momentum and thermal energy of mechanical ejecta in a self-consistent manner, accounting for SNe cooling radii when they are not resolved. Using idealized simulations of single SN explosions, we show that the FIRE-2 algorithm, independent of resolution, reproduces converged solutions in both energy and momentum. In contrast, common 'fully thermal' (energy-dump) or 'fully kinetic' (particle-kicking) schemes in the literature depend strongly on resolution: when applied at mass resolution \u2273100\u2009M\u2299, they diverge by orders of magnitude from the converged solution. In galaxy-formation simulations, this divergence leads to orders-of-magnitude differences in galaxy properties, unless those models are adjusted in a resolution-dependent way. We show that all models that individually time-resolve SNe converge to the FIRE-2 solution at sufficiently high resolution (<100\u2009M_\u2299). However, in both idealized single-SN simulations and cosmological galaxy-formation simulations, the FIRE-2 algorithm converges much faster than other sub-grid models without re-tuning parameters.",
"doi": "10.1093/mnras/sty674",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-06-21",
"series_number": "2",
"volume": "477",
"issue": "2",
"pages": "1578-1603"
},
{
"id": "authors:7a1k3-zkz83",
"collection": "authors",
"collection_id": "7a1k3-zkz83",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180627-143343177",
"type": "article",
"title": "Gas kinematics in FIRE simulated galaxies compared to spatially unresolved H\u2009I observations",
"author": [
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Bradford",
"given_name": "Jeremy",
"orcid": "0000-0002-2494-5995",
"clpid": "Bradford-Jeremy"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Geha",
"given_name": "Marla",
"orcid": "0000-0002-7007-9725",
"clpid": "Geha-Marla-C"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Weisz",
"given_name": "Daniel R.",
"orcid": "0000-0002-6442-6030",
"clpid": "Weisz-Daniel-R"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Fitts",
"given_name": "Alex",
"orcid": "0000-0002-8928-6011",
"clpid": "Fitts-Alex"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
}
],
"abstract": "The shape of a galaxy's spatially unresolved, globally integrated 21-cm emission line depends on its internal gas kinematics: galaxies with rotationally supported gas discs produce double-horned profiles with steep wings, while galaxies with dispersion-supported gas produce Gaussian-like profiles with sloped wings. Using mock observations of simulated galaxies from the FIRE project, we show that one can therefore constrain a galaxy's gas kinematics from its unresolved 21-cm line profile. In particular, we find that the kurtosis of the 21-cm line increases with decreasing V/\u03c3 and that this trend is robust across a wide range of masses, signal-to-noise ratios, and inclinations. We then quantify the shapes of 21-cm line profiles from a morphologically unbiased sample of \u223c2000 low-redshift, H\u2009I-detected galaxies with M_(star) = 10^(7\u221211)\u2009M_\u2299 and compare to the simulated galaxies. At M_(star) \u2273 10^(10)\u2009M_\u2299, both the observed and simulated galaxies produce double-horned profiles with low kurtosis and steep wings, consistent with rotationally supported discs. Both the observed and simulated line profiles become more Gaussian like (higher kurtosis and less-steep wings) at lower masses, indicating increased dispersion support. However, the simulated galaxies transition from rotational to dispersion support more strongly: at M_(star) = 10^(8\u221210)\u2009M_\u2299, most of the simulations produce more Gaussian-like profiles than typical observed galaxies with similar mass, indicating that gas in the low-mass simulated galaxies is, on average, overly dispersion supported. Most of the lower-mass-simulated galaxies also have somewhat lower gas fractions than the median of the observed population. The simulations nevertheless reproduce the observed line-width baryonic Tully\u2013Fisher relation, which is insensitive to rotational versus dispersion support.",
"doi": "10.1093/mnras/sty730",
"pmcid": "PMC6350816",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-06-21",
"series_number": "2",
"volume": "477",
"issue": "2",
"pages": "1536-1548"
},
{
"id": "authors:259ed-jz004",
"collection": "authors",
"collection_id": "259ed-jz004",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171031-184920974",
"type": "article",
"title": "Simulating galaxies in the reionization era with FIRE-2: morphologies and sizes",
"author": [
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
}
],
"abstract": "We study the morphologies and sizes of galaxies at z>5 using high-resolution\ncosmological zoom-in simulations from the Feedback In Realistic Environments\nproject. The galaxies show a variety of morphologies, from compact to clumpy to\nirregular. The simulated galaxies have more extended morphologies and larger\nsizes when measured using rest-frame optical B-band light than rest-frame UV\nlight; sizes measured from stellar mass surface density are even larger. The UV\nmorphologies are usually dominated by several small, bright young stellar\nclumps that are not always associated with significant stellar mass. The B-band\nlight traces stellar mass better than the UV, but it can also be biased by the\nbright clumps. At all redshifts, galaxy size correlates with stellar\nmass/luminosity with large scatter. The half-light radii range from 0.01 to 0.2\narcsec (0.05-1 kpc physical) at fixed magnitude. At z>5, the size of galaxies\nat fixed stellar mass/luminosity evolves as (1+z)^{-m}, with m~1-2. For\ngalaxies less massive than M_star~10^8 M_sun, the ratio of the half-mass radius\nto the halo virial radius is ~10% and does not evolve significantly at z = 5-10;\nthis ratio is typically 1-5% for more massive galaxies. A galaxy's \"observed\"\nsize decreases dramatically at shallower surface brightness limits. This effect\nmay account for the extremely small sizes of z>5 galaxies measured in the\nHubble Frontier Fields. We provide predictions for the cumulative light\ndistribution as a function of surface brightness for typical galaxies at z = 6.",
"doi": "10.1093/mnras/sty684",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-06-11",
"series_number": "1",
"volume": "477",
"issue": "1",
"pages": "219-229"
},
{
"id": "authors:99dmw-20a89",
"collection": "authors",
"collection_id": "99dmw-20a89",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180606-125451235",
"type": "article",
"title": "On the deuterium abundance and the importance of stellar mass loss in the interstellar and intergalactic medium",
"author": [
{
"family_name": "van de Voort",
"given_name": "Freeke",
"orcid": "0000-0002-6301-638X",
"clpid": "van-de-Voort-Freeke"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
}
],
"abstract": "We quantify the gas-phase abundance of deuterium and fractional contribution of stellar mass loss to the gas in cosmological zoom-in simulations from the Feedback In Realistic Environments project. At low metallicity, our simulations confirm that the deuterium abundance is very close to the primordial value. The chemical evolution of the deuterium abundance that we derive here agrees quantitatively with analytical chemical evolution models. We furthermore find that the relation between the deuterium and oxygen abundance exhibits very little scatter. We compare our simulations to existing high-redshift observations in order to determine a primordial deuterium fraction of (2.549 \u00b1 0.033) \u00d7 10^(\u22125) and stress that future observations at higher metallicity can also be used to constrain this value. At fixed metallicity, the deuterium fraction decreases slightly with decreasing redshift, due to the increased importance of mass-loss from intermediate-mass stars. We find that the evolution of the average deuterium fraction in a galaxy correlates with its star formation history. Our simulations are consistent with observations of the Milky Way's interstellar medium (ISM): the deuterium fraction at the solar circle is 85\u201392\u2009per cent of the primordial deuterium fraction. We use our simulations to make predictions for future observations. In particular, the deuterium abundance is lower at smaller galactocentric radii and in higher mass galaxies, showing that stellar mass loss is more important for fuelling star formation in these regimes (and can even dominate). Gas accreting on to galaxies has a deuterium fraction above that of the galaxies' ISM, but below the primordial fraction, because it is a mix of gas accreting from the intergalactic medium and gas previously ejected or stripped from galaxies.",
"doi": "10.1093/mnras/sty591",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-06-11",
"series_number": "1",
"volume": "477",
"issue": "1",
"pages": "80-92"
},
{
"id": "authors:ykwjg-kmw71",
"collection": "authors",
"collection_id": "ykwjg-kmw71",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170601-125207516",
"type": "article",
"title": "When Feedback Fails: The Scaling and Saturation of Star Formation Efficiency",
"author": [
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"clpid": "Grudi\u0107-M-Y"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "We present a suite of 3D multiphysics MHD simulations following star formation in isolated turbulent molecular gas discs ranging from 5 to 500 parsecs in radius. These simulations are designed to survey the range of surface densities between those typical of Milky Way giant molecular clouds (GMCs) (\u223c10^2M\u2299pc^(\u22122)) and extreme ultraluminous infrared galaxy environments (\u223c10^4M\u2299pc^(\u22122)) so as to map out the scaling of the cloud-scale star formation efficiency (SFE) between these two regimes. The simulations include prescriptions for supernova, stellar wind, and radiative feedback, which we find to be essential in determining both the instantaneous per-freefall (\u03b5_(ff)) and integrated (\u03b5_(int)) star formation efficiencies. In all simulations, the gas discs form stars until a critical stellar surface density has been reached and the remaining gas is blown out by stellar feedback. We find that surface density is a good predictor of \u03b5_(int), as suggested by analytic force balance arguments from previous works. SFE eventually saturates to \u223c1 at high surface density. We also find a proportional relationship between \u03b5_(ff) and \u03b5_(int), implying that star formation is feedback-moderated even over very short time-scales in isolated clouds. These results have implications for star formation in galactic discs, the nature and fate of nuclear starbursts, and the formation of bound star clusters. The scaling of \u03b5_(ff) with surface density is not consistent with the notion that \u03b5_(ff) is always \u223c 1\u2009per\u2009cent on the scale of GMCs, but our predictions recover the \u223c 1\u2009per\u2009cent value for GMC parameters similar to those found in spiral galaxies, including our own.",
"doi": "10.1093/mnras/sty035",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-04-11",
"series_number": "3",
"volume": "475",
"issue": "3",
"pages": "3511-3528"
},
{
"id": "authors:44fgk-5qq97",
"collection": "authors",
"collection_id": "44fgk-5qq97",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180328-133306899",
"type": "article",
"title": "Resonant Drag Instability of Grains Streaming in Fluids",
"author": [
{
"family_name": "Squire",
"given_name": "J.",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-J"
},
{
"family_name": "Hopkins",
"given_name": "P. F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We show that grains streaming through a fluid are generically unstable if their velocity, projected along some direction, matches the phase velocity of a fluid wave (linear oscillation). This can occur whenever grains stream faster than any fluid wave. The wave itself can be quite general\u2014sound waves, magnetosonic waves, epicyclic oscillations, and Brunt\u2013V\u00e4is\u00e4l\u00e4 oscillations each generate instabilities, for example. We derive a simple expression for the growth rates of these \"resonant drag instabilities\" (RDI). This expression (i) illustrates why such instabilities are so virulent and generic and (ii) allows for simple analytic computation of RDI growth rates and properties for different fluids. As examples, we introduce several new instabilities, which could see application across a variety of physical systems from atmospheres to protoplanetary disks, the interstellar medium, and galactic outflows. The matrix-based resonance formalism we introduce can also be applied more generally in other (nonfluid) contexts, providing a simple means for calculating and understanding the stability properties of interacting systems.",
"doi": "10.3847/2041-8213/aab54d",
"issn": "2041-8213",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2018-03-20",
"series_number": "1",
"volume": "856",
"issue": "1",
"pages": "Art. No. L15"
},
{
"id": "authors:d5jx6-h9398",
"collection": "authors",
"collection_id": "d5jx6-h9398",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180221-135659103",
"type": "article",
"title": "Formation of globular cluster candidates in merging proto-galaxies at high redshift: a view from the FIRE cosmological simulations",
"author": [
{
"family_name": "Kim",
"given_name": "Ji-hoon",
"orcid": "0000-0003-4464-1160",
"clpid": "Kim-Ji-hoon"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Grudi\u0107",
"given_name": "Michael Y.",
"orcid": "0000-0002-1655-5604",
"clpid": "Grudi\u0107-M-Y"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
}
],
"abstract": "Using a state-of-the-art cosmological simulation of merging proto-galaxies at high redshift from the FIRE project, with explicit treatments of star formation and stellar feedback in the interstellar medium, we investigate the formation of star clusters and examine one of the formation hypotheses of present-day metal-poor globular clusters. We find that frequent mergers in high-redshift proto-galaxies could provide a fertile environment to produce long-lasting bound star clusters. The violent merger event disturbs the gravitational potential and pushes a large gas mass of \u2273 10^(5\u20136)\u2009M\u2299 collectively to high density, at which point it rapidly turns into stars before stellar feedback can stop star formation. The high dynamic range of the reported simulation is critical in realizing such dense star-forming clouds with a small dynamical time-scale, t_(ff)\u2272 3\u2009Myr, shorter than most stellar feedback time-scales. Our simulation then allows us to trace how clusters could become virialized and tightly bound to survive for up to \u223c420\u2009Myr till the end of the simulation. Because the cluster's tightly bound core was formed in one short burst, and the nearby older stars originally grouped with the cluster tend to be preferentially removed, at the end of the simulation the cluster has a small age spread.",
"doi": "10.1093/mnras/stx2994",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-03-01",
"series_number": "3",
"volume": "474",
"issue": "3",
"pages": "4232-4244"
},
{
"id": "authors:5bs7a-1yh40",
"collection": "authors",
"collection_id": "5bs7a-1yh40",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171031-190653134",
"type": "article",
"title": "Modelling chemical abundance distributions for dwarf galaxies in the Local Group: the impact of turbulent metal diffusion",
"author": [
{
"family_name": "Escala",
"given_name": "Ivanna",
"orcid": "0000-0002-9933-9551",
"clpid": "Escala-I"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Kirby",
"given_name": "Evan N.",
"orcid": "0000-0001-6196-5162",
"clpid": "Kirby-E-N"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-C"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
}
],
"abstract": "We investigate stellar metallicity distribution functions (MDFs), including Fe and \u03b1-element abundances, in dwarf galaxies from the Feedback in Realistic Environment (FIRE) project. We examine both isolated dwarf galaxies and those that are satellites of a Milky Way-mass galaxy. In particular, we study the effects of including a sub-grid turbulent model for the diffusion of metals in gas. Simulations that include diffusion have narrower MDFs and abundance ratio distributions, because diffusion drives individual gas and star particles towards the average metallicity. This effect provides significantly better agreement with observed abundance distributions in dwarf galaxies in the Local Group, including small intrinsic scatter in [\u03b1/Fe] versus [Fe/H] of \u22720.1 dex. This small intrinsic scatter arises in our simulations because the interstellar medium in dwarf galaxies is well mixed at nearly all cosmic times, such that stars that form at a given time have similar abundances to \u22720.1 dex. Thus, most of the scatter in abundances at z = 0 arises from redshift evolution and not from instantaneous scatter in the ISM. We find similar MDF widths and intrinsic scatter for satellite and isolated dwarf galaxies, which suggests that environmental effects play a minor role compared with internal chemical evolution in our simulations. Overall, with the inclusion of metal diffusion, our simulations reproduce abundance distribution widths of observed low-mass galaxies, enabling detailed studies of chemical evolution in galaxy formation.",
"doi": "10.1093/mnras/stx2858",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-02-21",
"series_number": "2",
"volume": "474",
"issue": "2",
"pages": "2194-2211"
},
{
"id": "authors:qzh3e-s4q06",
"collection": "authors",
"collection_id": "qzh3e-s4q06",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180301-134435945",
"type": "article",
"title": "SDSS-IV MaNGA: constraints on the conditions for star formation in galaxy discs",
"author": [
{
"family_name": "Stark",
"given_name": "David V.",
"clpid": "Stark-David-V"
},
{
"family_name": "Bundy",
"given_name": "Kevin A.",
"orcid": "0000-0001-9742-3138",
"clpid": "Bundy-Kevin-A"
},
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-Matthew-E"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Westfall",
"given_name": "Kyle",
"clpid": "Westfall-Kyle-B"
},
{
"family_name": "Bershady",
"given_name": "Matthew",
"clpid": "Berhady-Matthew-A"
},
{
"family_name": "Li",
"given_name": "Cheng",
"orcid": "0000-0002-8280-3119",
"clpid": "Li-Cheng-CIT-Planetary Sciences"
},
{
"family_name": "Bizyaev",
"given_name": "Dmitry",
"clpid": "Bizyaev-Dmitry"
},
{
"family_name": "Masters",
"given_name": "Karen L.",
"orcid": "0000-0003-0846-9578",
"clpid": "Masters-Karen-L"
},
{
"family_name": "Weijmans",
"given_name": "Anne-Marie",
"clpid": "Weijmans-Anne-Marie"
},
{
"family_name": "Lacerna",
"given_name": "Ivan",
"clpid": "Lacerna-Ivan"
},
{
"family_name": "Thomas",
"given_name": "Daniel",
"orcid": "0000-0001-9415-5991",
"clpid": "Thomas-Dainel-A"
},
{
"family_name": "Drory",
"given_name": "Niv",
"clpid": "Drory-Niv"
},
{
"family_name": "Yan",
"given_name": "Renbin",
"clpid": "Yan-Renbin"
},
{
"family_name": "Zhang",
"given_name": "Kai",
"clpid": "Zhang-Kai"
}
],
"abstract": "Regions of disc galaxies with widespread star formation tend to be both gravitationally unstable and self-shielded against ionizing radiation, whereas extended outer discs with little or no star formation tend to be stable and unshielded on average. We explore what drives the transition between these two regimes, specifically whether discs first meet the conditions for self-shielding (parametrized by dust optical depth, \u03c4) or gravitational instability (parametrized by a modified version of Toomre's instability parameters, Qthermal, which quantifies the stability of a gas disc that is thermally supported at T = 104\u2009K). We first introduce a new metric formed by the product of these quantities, Qthermal\u03c4, which indicates whether the conditions for disc instability or self-shielding are easier to meet in a given region of a galaxy, and we discuss how Qthermal\u03c4 can be constrained even in the absence of direct gas information. We then analyse a sample of 13 galaxies with resolved gas measurements and find that on average galaxies will reach the threshold for disc instabilities (Qthermal < 1) before reaching the threshold for self-shielding (\u03c4 > 1). Using integral field spectroscopic observations of a sample of 236 galaxies from the Mapping Nearby Galaxies at APO (MaNGA) survey, we find that the value of Qthermal\u03c4 in star-forming discs is consistent with similar behaviour. These results support a scenario where disc fragmentation and collapse occurs before self-shielding, suggesting that gravitational instabilities are the primary condition for widespread star formation in galaxy discs. Our results support similar conclusions based on recent galaxy simulations.",
"doi": "10.1093/mnras/stx2903",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-02-21",
"series_number": "2",
"volume": "474",
"issue": "2",
"pages": "2323-2333"
},
{
"id": "authors:m8g2k-hvq02",
"collection": "authors",
"collection_id": "m8g2k-hvq02",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180216-074830560",
"type": "article",
"title": "Gas kinematics, morphology and angular momentum in the FIRE simulations",
"author": [
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Weisz",
"given_name": "Daniel R.",
"orcid": "0000-0002-6442-6030",
"clpid": "Weisz-Daniel-R"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Fitts",
"given_name": "Alex",
"orcid": "0000-0002-8928-6011",
"clpid": "Fitts-Alex"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-Shea"
}
],
"abstract": "We study the z = 0 gas kinematics, morphology and angular momentum content of isolated galaxies in a suite of cosmological zoom-in simulations from the FIRE project spanning M_(star) = 10^(6\u201311)\u2009M_\u2299. Gas becomes increasingly rotationally supported with increasing galaxy mass. In the lowest mass galaxies (M_(star) < 10^8\u2009M_\u2299), gas fails to form a morphological disc and is primarily dispersion and pressure supported. At intermediate masses (M_(star) = 10^(8\u201310)\u2009M_\u2299), galaxies display a wide range of gas kinematics and morphologies, from thin, rotating discs to irregular spheroids with negligible net rotation. All the high-mass (M_(star) = 10^(10\u201311)\u2009M_\u2299) galaxies form rotationally supported gas discs. Many of the haloes whose galaxies fail to form discs harbour high angular momentum gas in their circumgalactic medium. The ratio of the specific angular momentum of gas in the central galaxy to that of the dark matter halo increases significantly with galaxy mass, from \u3008j_(gas)\u3009/\u3008j_(DM)\u3009 \u223c 0.1 at \nM_(star) = 10^(6-7) M_\u2299 to \u3008j_(gas)\u3009/\u3008j_(DM)\u3009 \u223c 2 at M_(star) = 10^(10\u201311)\u2009M_\u2299. The reduced rotational support in the lowest mass galaxies owes to (a) stellar feedback and the UV background suppressing the accretion of high angular momentum gas at late times, and (b) stellar feedback driving large non-circular gas motions. We broadly reproduce the observed scaling relations between galaxy mass, gas rotation velocity, size and angular momentum, but may somewhat underpredict the incidence of disky, high angular momentum galaxies at the lowest observed masses (M_(star) = (10^6\u20132 \u00d7 10^7)\u2009M_\u2299). Stars form preferentially from low angular momentum gas near the galactic centre and are less rotationally supported than gas. The common assumption that stars follow the same rotation curve as gas thus substantially overestimates the simulated galaxies' stellar angular momentum, particularly at low masses.",
"doi": "10.1093/mnras/stx2482",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2018-01-11",
"series_number": "2",
"volume": "473",
"issue": "2",
"pages": "1930-1955"
},
{
"id": "authors:mt760-1je66",
"collection": "authors",
"collection_id": "mt760-1je66",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171031-193058430",
"type": "article",
"title": "Stellar feedback strongly alters the amplification and morphology of galactic magnetic fields",
"author": [
{
"family_name": "Su",
"given_name": "Kung-Yi",
"orcid": "0000-0003-1598-0083",
"clpid": "Su-Kung-Yi"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "Using high-resolution magnetohydrodynamic simulations of idealized, non-cosmological galaxies, we investigate how cooling, star formation and stellar feedback affect galactic magnetic fields. We find that the amplification histories, saturation values and morphologies of the magnetic fields vary considerably depending on the baryonic physics employed, primarily because of differences in the gas density distribution. In particular, adiabatic runs and runs with a subgrid (effective equation of state) stellar feedback model yield lower saturation values and morphologies that exhibit greater large-scale order compared with runs that adopt explicit stellar feedback and runs with cooling and star formation but no feedback. The discrepancies mostly lie in gas denser than the galactic average, which requires cooling and explicit fragmentation to capture. Independent of the baryonic physics included, the magnetic field strength scales with gas density as B \u221d n^(2/3), suggesting isotropic flux freezing or equipartition between the magnetic and gravitational energies during the field amplification. We conclude that accurate treatments of cooling, star formation and stellar feedback are crucial for obtaining the correct magnetic field strength and morphology in dense gas, which, in turn, is essential for properly modelling other physical processes that depend on the magnetic field, such as cosmic ray feedback.",
"doi": "10.1093/mnrasl/slx172",
"issn": "1745-3925",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society: Letters",
"publication_date": "2018-01-01",
"series_number": "1",
"volume": "473",
"issue": "1",
"pages": "L111-L115"
},
{
"id": "authors:f0zx3-h8195",
"collection": "authors",
"collection_id": "f0zx3-h8195",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171211-105754834",
"type": "article",
"title": "Dwarf galaxy mass estimators versus cosmological simulations",
"author": [
{
"family_name": "Gonz\u00e1lez-Samaniego",
"given_name": "Alejandro",
"orcid": "0000-0002-3708-4194",
"clpid": "Gonz\u00e1lez-Samaniego-Alejandro"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Fitts",
"given_name": "Alex",
"orcid": "0000-0002-8928-6011",
"clpid": "Fitts-Alex"
},
{
"family_name": "Elbert",
"given_name": "Oliver D.",
"orcid": "0000-0001-5464-6366",
"clpid": "Elbert-Oliver-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
}
],
"abstract": "We use a suite of high-resolution cosmological dwarf galaxy simulations to test the accuracy of commonly used mass estimators from Walker et al. (2009) and Wolf et al. (2010), both of which depend on the observed line-of-sight velocity dispersion and the 2D half-light radius of the galaxy, R_e. The simulations are part of the Feedback in Realistic Environments (FIRE) project and include 12 systems with stellar masses spanning 10^5\u201310^7\u2009M\u2299 that have structural and kinematic properties similar to those of observed dispersion-supported dwarfs. Both estimators are found to be quite accurate: M_(Wolf)/M_(true) = 0.98^(+0.19)_(\u22120.12) and M_(Walker)/M_(true) = 1.07^(+0.21)_(\u22120.15), with errors reflecting the 68\u2009per\u2009cent range over all simulations. The excellent performance of these estimators is remarkable given that they each assume spherical symmetry, a supposition that is broken in our simulated galaxies. Though our dwarfs have negligible rotation support, their 3D stellar distributions are flattened, with short-to-long axis ratios c/a \u2243 0.4\u20130.7. The median accuracy of the estimators shows no trend with asphericity. Our simulated galaxies have sphericalized stellar profiles in 3D that follow a nearly universal form, one that transitions from a core at small radius to a steep fall-off \u221dr^(\u22124.2) at large r; they are well fit by S\u00e9rsic profiles in projection. We find that the most important empirical quantity affecting mass estimator accuracy is R_e. Determining R_e by an analytic fit to the surface density profile produces a better estimated mass than if the half-light radius is determined via direct summation.",
"doi": "10.1093/mnras/stx2322",
"pmcid": "PMC6350817",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-12-21",
"series_number": "4",
"volume": "472",
"issue": "4",
"pages": "4786-4796"
},
{
"id": "authors:f09ez-x0m27",
"collection": "authors",
"collection_id": "f09ez-x0m27",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171103-075627443",
"type": "article",
"title": "SIDM on fire: hydrodynamical self-interacting dark matter simulations of low-mass dwarf galaxies",
"author": [
{
"family_name": "Robles",
"given_name": "Victor H.",
"orcid": "0000-0002-9497-9963",
"clpid": "Robles-Victor-H"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-James-S"
},
{
"family_name": "Elbert",
"given_name": "Oliver D.",
"orcid": "0000-0001-5464-6366",
"clpid": "Elbert-Oliver-D"
},
{
"family_name": "Fitts",
"given_name": "Alex",
"orcid": "0000-0002-8928-6011",
"clpid": "Fitts-Alex"
},
{
"family_name": "Gonz\u00e1lez-Samaniego",
"given_name": "Alejandro",
"orcid": "0000-0002-3708-4194",
"clpid": "Gonz\u00e1lez-Samaniego-Alejandro"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-Michael"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-Christopher-C"
}
],
"abstract": "We compare a suite of four simulated dwarf galaxies formed in 10^(10)\u2009\u2009M_\u2299 haloes of collisionless cold dark matter (CDM) with galaxies simulated in the same haloes with an identical galaxy formation model but a non-zero cross-section for DM self-interactions. These cosmological zoom-in simulations are part of the Feedback In Realistic Environments (FIRE) project and utilize the FIRE-2 model for hydrodynamics and galaxy formation physics. We find the stellar masses of the galaxies formed in self-interacting dark matter (SIDM) with \u03c3/m = 1\u2009cm^2\u2009g^(\u22121) are very similar to those in CDM (spanning M\u22c6 \u2248 10^(5.7\u20137.0)M_\u2299) and all runs lie on a similar stellar mass\u2013size relation. The logarithmic DM density slope (\u03b1 = d log\u2009\u03c1/d log\u2009r) in the central 250-500pc remains steeper than \u03b1 = \u22120.8 for the CDM-Hydro simulations with stellar mass M\u22c6 \u223c 10^(6.6)\u2009M_\u2299 and core-like in the most massive galaxy. In contrast, every SIDM hydrodynamic simulation yields a flatter profile, with \u03b1 > \u22120.4. Moreover, the central density profiles predicted in SIDM runs without baryons are similar to the SIDM runs that include FIRE-2 baryonic physics. Thus, SIDM appears to be much more robust to the inclusion of (potentially uncertain) baryonic physics than CDM on this mass scale, suggesting that SIDM will be easier to falsify than CDM using low-mass galaxies. Our FIRE simulations predict that galaxies less massive than M\u22c6 \u2272 3 \u00d7 10^6\u2009\u2009M_\u2299 provide potentially ideal targets for discriminating models, with SIDM producing substantial cores in such tiny galaxies and CDM producing cusps.",
"doi": "10.1093/mnras/stx2253",
"pmcid": "PMC6310025",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-12-11",
"series_number": "3",
"volume": "472",
"issue": "3",
"pages": "2945-2954"
},
{
"id": "authors:7p55k-y2x89",
"collection": "authors",
"collection_id": "7p55k-y2x89",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171102-145558477",
"type": "article",
"title": "Comparing models for IMF variation across cosmological time in Milky Way-like galaxies",
"author": [
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
}
],
"abstract": "One of the key observations regarding the stellar initial mass function (IMF) is its near-universality in the Milky Way (MW), which provides a powerful way to constrain different star formation models that predict the IMF. However, those models are almost universally 'cloud-scale' or smaller \u2013 they take as input or simulate single molecular clouds (GMCs), clumps or cores, and predict the resulting IMF as a function of the cloud properties. Without a model for the progenitor properties of all clouds that formed the stars at different locations in the MW (including ancient stellar populations formed in high redshift, likely gas-rich dwarf progenitor galaxies that looked little like the Galaxy today), the predictions cannot be fully explored nor safely applied to 'live' cosmological calculations of the IMF in different galaxies at different cosmological times. We therefore combine a suite of high-resolution cosmological simulations (from the Feedback In Realistic Environments project), which form MW-like galaxies with reasonable star formation properties and explicitly resolve massive GMCs, with various proposed cloud-scale IMF models. We apply the models independently to every star particle formed in the simulations to synthesize the predicted IMF in the present-day galaxy. We explore models where the IMF depends on Jeans mass, sonic or 'turbulent Bonnor\u2013Ebert' mass, fragmentation with a polytropic equation of state, or where it is self-regulated by protostellar feedback. We show that all of these models, except the feedback-regulated ones, predict far more variation (\u223c0.6\u20131\u2009dex 1\u03c3 scatter in the IMF turnover mass) in the simulations than is observed in the MW.",
"doi": "10.1093/mnras/stx2067",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-12",
"series_number": "2",
"volume": "472",
"issue": "2",
"pages": "2107-2116"
},
{
"id": "authors:260mm-s2898",
"collection": "authors",
"collection_id": "260mm-s2898",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180726-143711819",
"type": "article",
"title": "Black holes on FIRE: stellar feedback limits early feeding of galactic nuclei",
"author": [
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Torrey",
"given_name": "Paul",
"orcid": "0000-0002-5653-0786",
"clpid": "Torrey-P"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "We introduce massive black holes (BHs) in the Feedback In Realistic Environments (FIRE) project and perform high-resolution cosmological hydrodynamic simulations of quasar-mass haloes [Mhalo(z = 2) \u2248 10^(12.5)\u2009M_\u2299] down to z = 1. These simulations model stellar feedback by supernovae, stellar winds and radiation, and BH growth using a gravitational torque-based prescription tied to the resolved properties of galactic nuclei. We do not include BH feedback. We show that early BH growth occurs through short (\u22721\u2009Myr) accretion episodes that can reach or even exceed the Eddington rate. In this regime, BH growth is limited by bursty stellar feedback continuously evacuating gas from galactic nuclei, and BHs remain undermassive in low-mass galaxies relative to the local M_(BH)\u2013M_(bulge) relation. BH growth is more efficient at later times, when the nuclear stellar potential retains a significant gas reservoir, star formation becomes less bursty and galaxies settle into a more ordered state. BHs rapidly converge on to the observed scaling relations when the host reaches Mbulge \u223c 10^(10)\u2009M_\u2299. We show that resolving the effects of stellar feedback on the gas supply in the inner \u223c100\u2009pc of galaxies is necessary to accurately capture the growth of central BHs. Our simulations imply that bursty stellar feedback has important implications for BH\u2013galaxy relations, AGN demographics and time variability, the formation of early quasars and massive BH mergers.",
"doi": "10.1093/mnrasl/slx161",
"issn": "1745-3925",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society: Letters",
"publication_date": "2017-11-21",
"series_number": "1",
"volume": "472",
"issue": "1",
"pages": "L109-L114"
},
{
"id": "authors:wrfpq-g9d64",
"collection": "authors",
"collection_id": "wrfpq-g9d64",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171023-105621121",
"type": "article",
"title": "Stacked Star Formation Rate Profiles of Bursty Galaxies Exhibit \"Coherent\" Star Formation",
"author": [
{
"family_name": "Orr",
"given_name": "Matthew E.",
"orcid": "0000-0003-1053-3081",
"clpid": "Orr-M-E"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Nelson",
"given_name": "Erica J.",
"orcid": "0000-0002-7524-374X",
"clpid": "Nelson-E-J"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Schmitz",
"given_name": "Denise M.",
"orcid": "0000-0001-6297-9312",
"clpid": "Schmitz-D-M"
},
{
"family_name": "Miller",
"given_name": "Tim B.",
"clpid": "Miller-T-B"
}
],
"abstract": "In a recent work based on 3200 stacked H\u03b1 maps of galaxies at z ~ 1, Nelson et al. find evidence for \"coherent star formation\": the stacked star formation rate (SFR) profiles of galaxies above (below) the \"star formation main sequence\" (MS) are above (below) that of galaxies on the MS at all radii. One might interpret this result as inconsistent with highly bursty star formation and evidence that galaxies evolve smoothly along the MS rather than crossing it many times. We analyze six simulated galaxies at z ~ 1 from the Feedback in Realistic Environments (FIRE) project in a manner analogous to the observations to test whether the above interpretations are correct. The trends in stacked SFR profiles are qualitatively consistent with those observed. However, SFR profiles of individual galaxies are much more complex than the stacked profiles: the former can be flat or even peak at large radii because of the highly clustered nature of star formation in the simulations. Moreover, the SFR profiles of individual galaxies above (below) the MS are not systematically above (below) those of MS galaxies at all radii. We conclude that the time-averaged coherent star formation evident stacks of observed galaxies is consistent with highly bursty, clumpy star formation of individual galaxies and is not evidence that galaxies evolve smoothly along the MS.",
"doi": "10.3847/2041-8213/aa8f93",
"issn": "2041-8213",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2017-11-01",
"series_number": "1",
"volume": "849",
"issue": "1",
"pages": "Art. No. L2"
},
{
"id": "authors:srvmh-06j92",
"collection": "authors",
"collection_id": "srvmh-06j92",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170921-142943803",
"type": "article",
"title": "Fire in the field: simulating the threshold of galaxy formation",
"author": [
{
"family_name": "Fitts",
"given_name": "Alex",
"orcid": "0000-0002-8928-6011",
"clpid": "Fitts-A"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Elbert",
"given_name": "Oliver D.",
"clpid": "Elbert-O-D"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-J-S"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "O\u00f1orbe",
"given_name": "Jos\u00e9",
"clpid": "O\u00f1orbe-J"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-C"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Skillman",
"given_name": "Evan D.",
"clpid": "Skillman-E-D"
},
{
"family_name": "Weisz",
"given_name": "Daniel R.",
"orcid": "0000-0002-6442-6030",
"clpid": "Weisz-D-R"
}
],
"abstract": "We present a suite of 15 cosmological zoom-in simulations of isolated dark matter haloes, all with masses of M_(halo) \u2248 10^(10)\u2009M_\u2299 at z = 0, in order to understand the relationship among halo assembly, galaxy formation and feedback's effects on the central density structure in dwarf galaxies. These simulations are part of the Feedback in Realistic Environments (FIRE) project and are performed at extremely high resolution (m_(baryon) = 500\u2009M_\u2299, m_(dm) = 2500\u2009M_\u2299). The resultant galaxies have stellar masses that are consistent with rough abundance matching estimates, coinciding with the faintest galaxies that can be seen beyond the virial radius of the Milky Way (M_*/M_\u2299 \u2248 10^5 \u2212 10^7). This non-negligible spread in stellar mass at z = 0 in haloes within a narrow range of virial masses is strongly correlated with central halo density or maximum circular velocity V_(max), both of which are tightly linked to halo formation time. Much of this dependence of M_* on a second parameter (beyond M_(halo)) is a direct consequence of the M_(halo) \u223c 10^(10)\u2009M_\u2299 mass scale coinciding with the threshold for strong reionization suppression: the densest, earliest-forming haloes remain above the UV-suppression scale throughout their histories while late-forming systems fall below the UV-suppression scale over longer periods and form fewer stars as a result. In fact, the latest-forming, lowest-concentration halo in our suite fails to form any stars. Haloes that form galaxies with M_\u22c6 \u2273 2 \u00d7 10^6\u2009M_\u2299 have reduced central densities relative to dark-matter-only simulations, and the radial extent of the density modifications is well-approximated by the galaxy half-mass radius r_(1/2). Lower-mass galaxies do not modify their host dark matter haloes at the mass scale studied here. This apparent stellar mass threshold of M_\u22c6 \u2248 2 \u00d7 10^6 \u2212 2 \u00d7 10^(\u22124)\u2009M_(halo) is broadly consistent with previous work and provides a testable prediction of FIRE feedback models in \u039bcold dark matter.",
"doi": "10.1093/mnras/stx1757",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-11",
"series_number": "3",
"volume": "471",
"issue": "3",
"pages": "3547-3562"
},
{
"id": "authors:wgvvg-42f63",
"collection": "authors",
"collection_id": "wgvvg-42f63",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170921-132842035",
"type": "article",
"title": "The distribution of density in supersonic turbulence",
"author": [
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-J"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We propose a model for the statistics of the mass density in supersonic turbulence, which plays a crucial role in star formation and the physics of the interstellar medium (ISM). The model is derived by considering the density to be arranged as a collection of strong shocks of width \n\u223cM^(-2), where M is the turbulent Mach number. With two physically motivated parameters, the model predicts all density statistics for M > 1 turbulence: the density probability distribution and its intermittency (deviation from lognormality), the density variance\u2013Mach number relation, power spectra and structure functions. For the proposed model parameters, reasonable agreement is seen between model predictions and numerical simulations, albeit within the large uncertainties associated with current simulation results. More generally, the model could provide a useful framework for more detailed analysis of future simulations and observational data. Due to the simple physical motivations for the model in terms of shocks, it is straightforward to generalize to more complex physical processes, which will be helpful in future more detailed applications to the ISM. We see good qualitative agreement between such extensions and recent simulations of non-isothermal turbulence.",
"doi": "10.1093/mnras/stx1817",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-11",
"series_number": "3",
"volume": "471",
"issue": "3",
"pages": "3753-3767"
},
{
"id": "authors:nzaqs-x7g90",
"collection": "authors",
"collection_id": "nzaqs-x7g90",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170921-133516143",
"type": "article",
"title": "Not so lumpy after all: modelling the depletion of dark matter subhaloes by Milky Way-like galaxies",
"author": [
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-J-S"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Sanderson",
"given_name": "Robyn E.",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-R-E"
},
{
"family_name": "Graus",
"given_name": "Andrew S.",
"clpid": "Graus-A-S"
},
{
"family_name": "Kelley",
"given_name": "Tyler",
"clpid": "Kelley-T"
}
],
"abstract": "Among the most important goals in cosmology is detecting and quantifying small (M_(halo)\u224310^(6\u22129) M\u2299) dark matter (DM) subhaloes. Current probes around the Milky Way (MW) are most sensitive to such substructure within \u223c20 kpc of the halo centre, where the galaxy contributes significantly to the potential. We explore the effects of baryons on subhalo populations in \u039bCDM using cosmological zoom-in baryonic simulations of MW-mass haloes from the Latte simulation suite, part of the Feedback In Realistic Environments (FIRE) project. Specifically, we compare simulations of the same two haloes run using (1) DM-only (DMO), (2) full baryonic physics and (3) DM with an embedded disc potential grown to match the FIRE simulation. Relative to baryonic simulations, DMO simulations contain \u223c2 \u00d7 as many subhaloes within 100 kpc of the halo centre; this excess is \u22735 \u00d7 within 25 kpc. At z = 0, the baryonic simulations are completely devoid of subhaloes down to 3\u00d710^6M\u2299 within 15 kpc of the MW-mass galaxy, and fewer than 20 surviving subhaloes have orbital pericentres <20\u2009kpc. Despite the complexities of baryonic physics, the simple addition of an embedded central disc potential to DMO simulations reproduces this subhalo depletion, including trends with radius, remarkably well. Thus, the additional tidal field from the central galaxy is the primary cause of subhalo depletion. Subhaloes on radial orbits that pass close to the central galaxy are preferentially destroyed, causing the surviving population to have tangentially biased orbits compared to DMO predictions. Our method of embedding a potential in DMO simulations provides a fast and accurate alternative to full baryonic simulations, thus enabling suites of cosmological simulations that can provide accurate and statistical predictions of substructure populations.",
"doi": "10.1093/mnras/stx1710",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-10",
"series_number": "2",
"volume": "471",
"issue": "2",
"pages": "1709-1727"
},
{
"id": "authors:27v96-02864",
"collection": "authors",
"collection_id": "27v96-02864",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161212-093805711",
"type": "article",
"title": "Feedback first: the surprisingly weak effects of magnetic fields, viscosity, conduction and metal diffusion on sub-L* galaxy formation",
"author": [
{
"family_name": "Su",
"given_name": "Kung-Yi",
"orcid": "0000-0003-1598-0083",
"clpid": "Su-Kung-Yi"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Robles",
"given_name": "Victor H.",
"orcid": "0000-0002-9497-9963",
"clpid": "Robles-V-H"
}
],
"abstract": "Using high-resolution simulations with explicit treatment of stellar feedback physics based on the FIRE (Feedback In Realistic Environments) project, we study how galaxy formation and the interstellar medium (ISM) are affected by magnetic fields, anisotropic Spitzer\u2013Braginskii conduction and viscosity, and sub-grid metal diffusion from unresolved turbulence. We consider controlled simulations of isolated (non-cosmological) galaxies but also a limited set of cosmological 'zoom-in' simulations. Although simulations have shown significant effects from these physics with weak or absent stellar feedback, the effects are much weaker than those of stellar feedback when the latter is modelled explicitly. The additional physics have no systematic effect on galactic star formation rates (SFRs). In contrast, removing stellar feedback leads to SFRs being overpredicted by factors of \u223c10\u2013100. Without feedback, neither galactic winds nor volume-filling hot-phase gas exist, and discs tend to runaway collapse to ultra-thin scaleheights with unphysically dense clumps congregating at the galactic centre. With stellar feedback, a multi-phase, turbulent medium with galactic fountains and winds is established. At currently achievable resolutions and for the investigated halo mass range 10^(10)\u201310^(13)\u2009M\u2299, the additional physics investigated here (magnetohydrodynamic, conduction, viscosity, metal diffusion) have only weak (\u223c10\u2009per\u2009cent-level) effects on regulating SFR and altering the balance of phases, outflows or the energy in ISM turbulence, consistent with simple equipartition arguments. We conclude that galactic star formation and the ISM are primarily governed by a combination of turbulence, gravitational instabilities and feedback. We add the caveat that active galactic nucleus feedback is not included in the present work.",
"doi": "10.1093/mnras/stx1463",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-10",
"series_number": "1",
"volume": "471",
"issue": "1",
"pages": "144-166"
},
{
"id": "authors:savrr-3m978",
"collection": "authors",
"collection_id": "savrr-3m978",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190130-121936352",
"type": "article",
"title": "Better Galactic Mass Models through Chemistry",
"author": [
{
"family_name": "Sanderson",
"given_name": "Robyn E.",
"orcid": "0000-0003-3939-3297",
"clpid": "Sanderson-R-E"
},
{
"family_name": "Wetzel",
"given_name": "Andrew R.",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Sharma",
"given_name": "Sanjib",
"orcid": "0000-0002-0920-809X",
"clpid": "Sharma-Sanjib"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "With the upcoming release of the Gaia catalog and the many multiplexed spectroscopic surveys on the horizon, we are rapidly moving into a new data-driven era in the study of the Milky Way's stellar halo. When combined, these data sets will give us a many-dimensional view of stars in accreted structures in the halo that includes both dynamical information about their orbits and chemical information about their formation histories. Using simulated data from the state-of-the-art Latte simulations of Milky-Way-like galaxies, which include hydrodynamics, feedback, and chemical evolution in a cosmological setting, we demonstrate that while dynamical information alone can be used to constrain models of the Galactic mass distribution in the halo, including the extra dimensions provided by chemical abundances can improve these constraints as well as assist in untangling different accreted components.",
"doi": "10.3390/galaxies5030043",
"issn": "2075-4434",
"publisher": "MDPI",
"publication": "Galaxies",
"publication_date": "2017-09",
"series_number": "3",
"volume": "5",
"issue": "3",
"pages": "Art. No. 43"
},
{
"id": "authors:nkx6a-jj304",
"collection": "authors",
"collection_id": "nkx6a-jj304",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170908-093448095",
"type": "article",
"title": "Gaia Reveals a Metal-rich, in situ Component of the Local Stellar Halo",
"author": [
{
"family_name": "Bonaca",
"given_name": "Ana",
"orcid": "0000-0002-7846-9787",
"clpid": "Bonaca-A"
},
{
"family_name": "Conroy",
"given_name": "Charlie",
"orcid": "0000-0002-1590-8551",
"clpid": "Conroy-C"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "We use the first Gaia data release, combined with the RAVE and APOGEE spectroscopic surveys, to investigate the origin of halo stars within \u227e3 kpc from the Sun. We identify halo stars kinematically as moving at a relative speed of at least 220 km s^(\u22121) with respect to the local standard of rest. These stars are generally less metal-rich than the disk, but surprisingly, half of our halo sample is comprised of stars with [Fe/H] > -1. The orbital directions of these metal-rich halo stars are preferentially aligned with the disk rotation, in sharp contrast with the intrinsically isotropic orbital distribution of the metal-poor halo stars. We find similar properties in the Latte cosmological zoom-in simulation of a Milky Way-like galaxy from the FIRE project. In Latte, metal-rich halo stars formed primarily inside of the solar circle, whereas lower-metallicity halo stars preferentially formed at larger distances (extending beyond the virial radius). This suggests that metal-rich halo stars in the solar neighborhood actually formed in situ within the Galactic disk, rather than having been accreted from satellite systems. These stars, currently on halo-like orbits, therefore have likely undergone substantial radial migration/heating.",
"doi": "10.3847/1538-4357/aa7d0c",
"issn": "1538-4357",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2017-08-20",
"series_number": "2",
"volume": "845",
"issue": "2",
"pages": "Art. No. 101"
},
{
"id": "authors:ddz95-9v625",
"collection": "authors",
"collection_id": "ddz95-9v625",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170828-090207603",
"type": "article",
"title": "The dynamics of charged dust in magnetized molecular clouds",
"author": [
{
"family_name": "Lee",
"given_name": "Hyunseok",
"clpid": "Lee-Hyunseok"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-J"
}
],
"abstract": "We study the dynamics of large, charged dust grains in turbulent giant molecular clouds (GMCs). Massive dust grains behave as aerodynamic particles in primarily neutral dense gas, and thus are able to produce dramatic small-scale fluctuations in the dust-to-gas ratio. Hopkins & Lee directly simulated the dynamics of neutral dust grains in supersonic magnetohydrodynamic turbulence, typical of GMCs, and showed that the dust-to-gas fluctuations can exceed factor \u223c1000 on small scales, with important implications for star formation, stellar abundances and dust behaviour and growth. However, even in primarily neutral gas in GMCs, dust grains are negatively charged and Lorentz forces are non-negligible. Therefore, we extend our previous study by including the effects of Lorentz forces on charged grains (in addition to drag). For small-charged grains (sizes \u226a 0.1\u2009\u03bcm), Lorentz forces suppress dust-to-gas ratio fluctuations, while for large grains (sizes \u2273 1\u2009\u03bcm), Lorentz forces have essentially no effect, trends that are well explained with a simple theory of dust magnetization. In some special intermediate cases, Lorentz forces can enhance dust\u2013gas segregation. Regardless, for the physically expected scaling of dust charge with grain size, we find the most important effects depend on grain size (via the drag equation) with Lorentz forces/charge as a second-order correction. We show that the dynamics we consider are determined by three dimensionless numbers in the limit of weak background magnetic fields: the turbulent Mach number, a dust drag parameter (proportional to grain size) and a dust Lorentz parameter (proportional to grain charge); these allow us to generalize our simulations to a wide range of conditions.",
"doi": "10.1093/mnras/stx1097",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-08",
"series_number": "3",
"volume": "469",
"issue": "3",
"pages": "3532-3540"
},
{
"id": "authors:a8s22-z7f36",
"collection": "authors",
"collection_id": "a8s22-z7f36",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170828-142126693",
"type": "article",
"title": "Low-redshift Lyman limit systems as diagnostics of cosmological inflows and outflows",
"author": [
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-Norman-W"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We use cosmological hydrodynamic simulations with stellar feedback from the FIRE (Feedback In Realistic Environments) project to study the physical nature of Lyman limit systems (LLSs) at z \u2264 1. At these low redshifts, LLSs are closely associated with dense gas structures surrounding galaxies, such as galactic winds, dwarf satellites and cool inflows from the intergalactic medium. Our analysis is based on 14 zoom-in simulations covering the halo mass range M_h \u2248 10^9\u201310^(13) M\u2299 at z = 0, which we convolve with the dark matter halo mass function to produce cosmological statistics. We find that the majority of cosmologically selected LLSs are associated with haloes in the mass range 10^(10) \u2272 M_h \u2272 10^(12)\u2009M\u2299. The incidence and H\u2009I column density distribution of simulated absorbers with columns in the range 10^(16.2)\u2264N_(HI)\u22642\u00d710^(20) Cm^(\u22122) are consistent with observations. High-velocity outflows (with radial velocity exceeding the halo circular velocity by a factor of \u2273 2) tend to have higher metallicities ([X/H] \u223c \u22120.5) while very low metallicity ([X/H] < \u22122) LLSs are typically associated with gas infalling from the intergalactic medium. However, most LLSs occupy an intermediate region in metallicity-radial velocity space, for which there is no clear trend between metallicity and radial kinematics. The overall simulated LLS metallicity distribution has a mean (standard deviation) [X/H] = \u22120.9 (0.4) and does not show significant evidence for bimodality, in contrast to recent observational studies, but consistent with LLSs arising from haloes with a broad range of masses and metallicities.",
"doi": "10.1093/mnras/stx952",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-08",
"series_number": "2",
"volume": "469",
"issue": "2",
"pages": "2292-2304"
},
{
"id": "authors:x3cqv-f4n64",
"collection": "authors",
"collection_id": "x3cqv-f4n64",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170828-091308390",
"type": "article",
"title": "Colours, star formation rates and environments of star-forming and quiescent galaxies at the cosmic noon",
"author": [
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "We analyse the star formation rates (SFRs), colours and dust extinctions of galaxies in massive (10^(12.5) \u2013 10^(13.5)M\u2299) haloes at z \u223c 2 in high-resolution, cosmological zoom-in simulations as part of the Feedback In Realistic Environments (FIRE) project. The simulations do not model feedback from active galactic nuclei (AGNs) but reproduce well the observed relations between stellar and halo mass and between stellar mass and SFR. About half (a third) of the simulated massive galaxies (massive central galaxies) at z \u223c 2 have broad-band colours classifying them as 'quiescent', and the fraction of quiescent centrals is steeply decreasing towards higher redshift, in agreement with observations. The progenitors of z \u223c 2 quiescent central galaxies are, on average, more massive, have lower specific SFRs and reside in more massive haloes than the progenitors of similarly massive star-forming centrals. The simulations further predict a morphological mix of galaxies that includes disc-dominated, irregular and early-type galaxies. However, our simulations do not reproduce the reddest of the quiescent galaxies observed at z \u223c 2. We also do not find evidence for a colour bimodality, but are limited by our modest sample size. In our simulations, the star formation activity of central galaxies of moderate mass (M_(star) \u223c 10^(10) \u2013 10^(11)M\u2299) is affected by a combination of two distinct physical processes. Outflows powered by stellar feedback result in a short-lived (<100 Myr), but almost complete, suppression of star formation activity after which many galaxies quickly recover and continue to form stars at normal rates. In addition, galaxies residing in slowly growing haloes tend to experience a moderate reduction of their SFRs ('cosmological starvation'). The relative importance of these processes and AGN feedback is uncertain and will be explored in future work.",
"doi": "10.1093/mnras/stx1120",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-08",
"series_number": "1",
"volume": "470",
"issue": "1",
"pages": "1050-1072"
},
{
"id": "authors:4qjjc-e8k45",
"collection": "authors",
"collection_id": "4qjjc-e8k45",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170803-083236533",
"type": "article",
"title": "Testing the Recovery of Intrinsic Galaxy Sizes and Masses of z \u223c 2 Massive Galaxies Using Cosmological Simulations",
"author": [
{
"family_name": "Price",
"given_name": "Sedona H.",
"orcid": "0000-0002-0108-4176",
"clpid": "Price-S-H"
},
{
"family_name": "Kriek",
"given_name": "Mariska",
"orcid": "0000-0002-7613-9872",
"clpid": "Kriek-M"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Barro",
"given_name": "Guillermo",
"orcid": "0000-0001-6813-875X",
"clpid": "Barro-G"
}
],
"abstract": "Accurate measurements of galaxy masses and sizes are key to tracing galaxy evolution over time. Cosmological zoom-in simulations provide an ideal test bed for assessing the recovery of galaxy properties from observations. Here, we utilize galaxies with M_* ~ 10^10 - 10^(11.5) M_\u2609 at z ~ 1.7\u20132 from the MassiveFIRE cosmological simulation suite, part of the Feedback in Realistic Environments (FIRE) project. Using mock multi-band images, we compare intrinsic galaxy masses and sizes to observational estimates. We find that observations accurately recover stellar masses, with a slight average underestimate of ~ 0.06 dex and a ~ 0.15 dex scatter. Recovered half-light radii agree well with intrinsic half-mass radii when averaged over all viewing angles, with a systematic offset of ~ 0.1 dex (with the half-light radii being larger) and a scatter of ~ 0.2 dex. When using color gradients to account for mass-to-light variations, recovered half-mass radii also exceed the intrinsic half-mass radii by ~ 1 dex. However, if not properly accounted for, aperture effects can bias size estimates by ~ 0.1 dex. No differences are found between the mass and size offsets for star-forming and quiescent galaxies. Variations in viewing angle are responsible for ~25% of the scatter in the recovered masses and sizes. Our results thus suggest that the intrinsic scatter in the mass\u2013size relation may have previously been overestimated by ~25%. Moreover, orientation-driven scatter causes the number density of very massive galaxies to be overestimated by ~ 0.5 dex at M_* ~ 10^(11.5) M_\u2609_.",
"doi": "10.3847/2041-8213/aa7d4b",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2017-07-20",
"series_number": "1",
"volume": "844",
"issue": "1",
"pages": "Art. No. L6"
},
{
"id": "authors:3mke0-xsn36",
"collection": "authors",
"collection_id": "3mke0-xsn36",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170707-070944289",
"type": "article",
"title": "High Angular Momentum Halo Gas: A Feedback and Code-independent Prediction of LCDM",
"author": [
{
"family_name": "Stewart",
"given_name": "Kyle R.",
"clpid": "Stewart-K-R"
},
{
"family_name": "Maller",
"given_name": "Ariyeh H.",
"clpid": "Maller-A-H"
},
{
"family_name": "O\u00f1orbe",
"given_name": "Jos\u00e9",
"clpid": "O\u00f1orbe-J"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-J-S"
},
{
"family_name": "Joung",
"given_name": "M. Ryan",
"clpid": "Joung-M-R"
},
{
"family_name": "Devriendt",
"given_name": "Julien",
"clpid": "Devriendt-J"
},
{
"family_name": "Ceverino",
"given_name": "Daniel",
"orcid": "0000-0002-8680-248X",
"clpid": "Ceverino-D"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
}
],
"abstract": "We investigate angular momentum acquisition in Milky Way-sized galaxies by comparing five high resolution zoom-in simulations, each implementing identical cosmological initial conditions but utilizing different hydrodynamic codes: Enzo, Art, Ramses, Arepo, and Gizmo-PSPH. Each code implements a distinct set of feedback and star formation prescriptions. We find that while many galaxy and halo properties vary between the different codes (and feedback prescriptions), there is qualitative agreement on the process of angular momentum acquisition in the galaxy's halo. In all simulations, cold filamentary gas accretion to the halo results in ~4 times more specific angular momentum in cold halo gas (\u03bb_(cold) \u2273 0.1) than in the dark matter halo. At z > 1, this inflow takes the form of inspiraling cold streams that are co-directional in the halo of the galaxy and are fueled, aligned, and kinematically connected to filamentary gas infall along the cosmic web. Due to the qualitative agreement among disparate simulations, we conclude that the buildup of high angular momentum halo gas and the presence of these inspiraling cold streams are robust predictions of Lambda Cold Dark Matter galaxy formation, though the detailed morphology of these streams is significantly less certain. A growing body of observational evidence suggests that this process is borne out in the real universe.",
"doi": "10.3847/1538-4357/aa6dff",
"issn": "1538-4357",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2017-07-01",
"series_number": "1",
"volume": "843",
"issue": "1",
"pages": "Art. No. 47"
},
{
"id": "authors:n9hs8-h4q75",
"collection": "authors",
"collection_id": "n9hs8-h4q75",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170629-101035094",
"type": "article",
"title": "Metal flows of the circumgalactic medium, and the metal budget in galactic haloes",
"author": [
{
"family_name": "Muratov",
"given_name": "Alexander L.",
"clpid": "Muratov-Alexander-L"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-Daniel"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Torrey",
"given_name": "Paul",
"orcid": "0000-0002-5653-0786",
"clpid": "Torrey-Paul"
},
{
"family_name": "Hafen",
"given_name": "Zachary H.",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-Norman-W"
}
],
"abstract": "We present an analysis of the flow of metals through the circumgalactic medium (CGM) in the Feedback in Realistic Environments (FIRE) simulations of galaxy formation, ranging from isolated dwarfs to L* galaxies. We find that nearly all metals produced in high-redshift galaxies are carried out in winds that reach 0.25R_(vir). When measured at 0.25R_(vir) the metallicity of outflows is slightly higher than the interstellar medium (ISM) metallicity. Many metals thus reside in the CGM. Cooling and recycling from this reservoir determine the metal budget in the ISM. The outflowing metal flux decreases by a factor of \u223c2\u20135 between 0.25R_(vir) and R_(vir). Furthermore, outflow metallicity is typically lower at R_(vir) owing to dilution of the remaining outflow by metal-poor material swept up from the CGM. The inflow metallicity at R_(vir) is generally low, but outflow and inflow metallicities are similar in the inner halo. At low redshift, massive galaxies no longer generate outflows that reach the CGM, causing a divergence in CGM and ISM metallicity. Dwarf galaxies continue to generate outflows, although they preferentially retain metal ejecta. In all but the least massive galaxy considered, a majority of the metals are within the halo at z = 0. We measure the fraction of metals in CGM, ISM and stars, and quantify the thermal state of CGM metals in each halo. The total amount of metals in the low-redshift CGM of two simulated L* galaxies is consistent with estimates from the Cosmic Origin Spectrograph haloes survey, while for the other two it appears to be lower.",
"doi": "10.1093/mnras/stx667",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-07",
"series_number": "4",
"volume": "468",
"issue": "4",
"pages": "4170-4188"
},
{
"id": "authors:d7y7e-mg136",
"collection": "authors",
"collection_id": "d7y7e-mg136",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170629-103507286",
"type": "article",
"title": "Protostellar feedback in turbulent fragmentation: consequences for stellar clustering and multiplicity",
"author": [
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Krumholz",
"given_name": "Mark R.",
"orcid": "0000-0003-3893-854X",
"clpid": "Krumholz-M-R"
}
],
"abstract": "Stars are strongly clustered on both large (\u223cpc) and small (\u223cbinary) scales, but there are few analytic or even semi-analytic theories for the correlation function and multiplicity of stars. In this paper, we present such a theory, based on our recently developed semi-analytic framework called MISFIT (Minimalistic Star Formation Including Turbulence), which models gravito-turbulent fragmentation, including the suppression of fragmentation by protostellar radiation feedback. We compare the results including feedback to a control model in which it is omitted. We show that both classes of models robustly reproduce the stellar correlation function at >0.01\u2009pc scales, which is well approximated by a power law that follows generally from scale-free physics (turbulence plus gravity) on large scales. On smaller scales, protostellar disc fragmentation becomes dominant over common core fragmentation, leading to a steepening of the correlation function. Multiplicity is more sensitive to feedback: we found that a model with the protostellar heating reproduces the observed multiplicity fractions and mass ratio distributions for both Solar and sub-Solar mass stars (in particular, the brown dwarf desert), while a model without feedback fails to do so. The model with feedback also produces an at-formation period distribution consistent with the one inferred from observations. However, it is unable to produce short-range binaries below the length-scale of protostellar discs. We suggest that such close binaries are produced primarily by disc fragmentation and further decrease their separation through orbital decay.",
"doi": "10.1093/mnras/stx725",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-07",
"series_number": "4",
"volume": "468",
"issue": "4",
"pages": "4093-4106"
},
{
"id": "authors:ew9d4-smv18",
"collection": "authors",
"collection_id": "ew9d4-smv18",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170914-073539583",
"type": "article",
"title": "The cosmic baryon cycle and galaxy mass assembly in the FIRE simulations",
"author": [
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
}
],
"abstract": "We use cosmological simulations from the FIRE (Feedback In Realistic Environments) project to study the baryon cycle and galaxy mass assembly for central galaxies in the halo mass range Mhalo \u223c 10^(10)\u201310^(13) M_\u2299. By tracing cosmic inflows, galactic outflows, gas recycling and merger histories, we quantify the contribution of physically distinct sources of material to galaxy growth. We show that in situ star formation fuelled by fresh accretion dominates the early growth of galaxies of all masses, while the re-accretion of gas previously ejected in galactic winds often dominates the gas supply for a large portion of every galaxy's evolution. Externally processed material contributes increasingly to the growth of central galaxies at lower redshifts. This includes stars formed ex situ and gas delivered by mergers, as well as smooth intergalactic transfer of gas from other galaxies, an important but previously underappreciated growth mode. By z = 0, wind transfer, i.e. the exchange of gas between galaxies via winds, can dominate gas accretion on to \u223cL* galaxies over fresh accretion and standard wind recycling. Galaxies of all masses re-accrete \u227350 per cent of the gas ejected in winds and recurrent recycling is common. The total mass deposited in the intergalactic medium per unit stellar mass formed increases in lower mass galaxies. Re-accretion of wind ejecta occurs over a broad range of time-scales, with median recycling times (\u223c100\u2013350 Myr) shorter than previously found. Wind recycling typically occurs at the scale radius of the halo, independent of halo mass and redshift, suggesting a characteristic recycling zone around galaxies that scales with the size of the inner halo and the galaxy's stellar component.",
"doi": "10.1093/mnras/stx1517",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-06-20",
"series_number": "4",
"volume": "470",
"issue": "4",
"pages": "4698-4719"
},
{
"id": "authors:pxhys-tw307",
"collection": "authors",
"collection_id": "pxhys-tw307",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170428-153015888",
"type": "article",
"title": "Forward and backward galaxy evolution in comoving cumulative number density space",
"author": [
{
"family_name": "Torrey",
"given_name": "Paul",
"orcid": "0000-0002-5653-0786",
"clpid": "Torrey-P"
},
{
"family_name": "Wellons",
"given_name": "Sarah",
"clpid": "Wellons-S"
},
{
"family_name": "Ma",
"given_name": "Chung-Pei",
"clpid": "Ma-Chung-Pei"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Vogelsberger",
"given_name": "Mark",
"orcid": "0000-0001-8593-7692",
"clpid": "Vogelsberger-M"
}
],
"abstract": "Galaxy cumulative comoving number density is commonly used to forge progenitor/descendant links between observed galaxy populations at different epochs. However, this method breaks down in the presence of galaxy mergers, or when galaxies experience stochastic growth rates. We present a simple analytic framework to treat the physical processes that drive the evolution and diffusion of galaxies within comoving number density space. The evolution in mass rank order of a galaxy population with time is influenced by (1) the non-conservative nature of total galaxy number density driven by galaxies combining in mergers (which we tabulate as a galaxy 'coagulation' rate) and (2) galaxy 'mass rank scatter' driven by stochasticity in stellar-mass growth rates from in situ star formation and mergers. We quantify the relative contribution of these two effects to the total mass rank order evolution using the Illustris simulation. We show that galaxy coagulation is dominant at lower redshifts and stellar masses, while scattered growth rates dominate the mass rank evolution at higher redshifts and stellar masses. For a galaxy population at 10^(10)\u2009M\u2299, coagulation has been the dominant effect since z = 2.2, but a galaxy population at 10^(11)\u2009M\u2299 was dominated by mass rank scatter until z = 0.6. We show that although the forward and backward median cumulative number density evolution tracks are asymmetric, the backward median cumulative number density evolution can be obtained by convolving the descendant distribution function with progenitor relative abundances. We tabulate fits for the median cumulative number density evolution and scatter that can be applied to improve the way galaxy populations are linked in multi-epoch observational data sets.",
"doi": "10.1093/mnras/stx370",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-06",
"series_number": "4",
"volume": "467",
"issue": "4",
"pages": "4872-4885"
},
{
"id": "authors:c0xns-jc579",
"collection": "authors",
"collection_id": "c0xns-jc579",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170531-105304416",
"type": "article",
"title": "Converging on the Initial Mass Function of Stars",
"author": [
{
"family_name": "Federrath",
"given_name": "Christoph",
"clpid": "Federrath-C"
},
{
"family_name": "Krumholz",
"given_name": "Mark",
"orcid": "0000-0003-3893-854X",
"clpid": "Krumholz-M-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Understanding the origin of stellar masses\u2014the initial mass function (IMF)\u2014 remains one of the most challenging problems in astrophysics. The IMF is a key ingredient for simulations of galaxy formation and evolution, and is used to calibrate star formation relations in extra-galactic observations. Modeling the IMF directly in hydrodynamical simulations has been attempted in several previous studies, but the most important processes that control the IMF remain poorly understood. This is because predicting the IMF from direct hydrodynamical simulations involves complex physics such as turbulence, magnetic fields, radiation feedback and mechanical feedback, all of which are difficult to model and the methods used have limitations in terms of accuracy and computational efficiency. Moreover, a physical interpretation of the simulated IMFs requires a numerically converged solution at high resolution, which has so far not been convincingly demonstrated. Here we present a resolution study of star cluster formation aimed at producing a converged IMF. We compare a set of magnetohydrodynamical (MHD) adaptive-mesh-refinement simulations with three different implementations of the thermodynamics of the gas: 1) with an isothermal equation of state (EOS), 2) with a polytropic EOS, and 3) with a simple stellar heating feedback model. We show that in the simulations with an isothermal or polytropic EOS, the number of stars and their mass distributions depend on the numerical resolution. By contrast, the simulations that employ the simple radiative feedback module demonstrate convergence in the number of stars formed and in their IMFs.",
"doi": "10.1088/1742-6596/837/1/012007",
"issn": "1742-6588",
"publisher": "IOP",
"publication": "Journal of Physics Conference Series",
"publication_date": "2017-05-30",
"volume": "837",
"pages": "Art. No. 012007"
},
{
"id": "authors:jjdgj-59229",
"collection": "authors",
"collection_id": "jjdgj-59229",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170505-063223827",
"type": "article",
"title": "Mufasa: Galaxy star formation, gas, and metal properties across cosmic time",
"author": [
{
"family_name": "Dav\u00e9",
"given_name": "Romeel",
"clpid": "Dav\u00e9-R"
},
{
"family_name": "Rafieferantsoa",
"given_name": "Mika H.",
"clpid": "Rafieferantsoa-M-H"
},
{
"family_name": "Thompson",
"given_name": "Robert J.",
"clpid": "Thompson-R-J"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We examine galaxy star formation rates (SFRs), metallicities and gas contents predicted by the Mufasa cosmological hydrodynamic simulations, which employ meshless hydrodynamics and novel feedback prescriptions that yield a good match to observed galaxy stellar mass assembly. We combine 50, 25 and 12.5\u2009h^(\u22121)\u2009Mpc boxes with a quarter billion particles each to show that Mufasa broadly reproduces a wide range of relevant observations, including SFR and specific SFR functions, the mass\u2013metallicity relation, H\u2009i and H2 fractions, H\u2009i (21 cm) and CO luminosity functions, and cosmic gas density evolution. There are mild but significant discrepancies, such as perhaps too many high-SFR galaxies, overly metal-rich and H\u2009i-poor galaxies at M^* \u2273 2 \u00d7 10^(10)\u2009M_\u2299, and specific star formation rates that are too low at z \u223c 1\u20132. The H\u2009i mass function increases by \u00d72 out to z \u223c 1, then steepens to higher redshifts, while the CO luminosity function computed using the Narayanan et al. conversion factor shows a rapid increase of CO-bright galaxies out to z \u223c 2 in accord with data. \u03a9_(HI) and \u03a9H2 both scale roughly as \u221d(1 + z)^(0.7) out to z \u223c 3, comparable to the rise in H\u2009i and H2 fractions. Mufasa galaxies with high SFR at a given M* have lower metallicities and higher H\u2009i and H2 fractions, following observed trends; we make quantitative predictions for how the fluctuations in the baryon cycle drive correlated scatter around galaxy scaling relations. Most of these trends are well converged with numerical resolution. These successes highlight Mufasa as a viable platform to study many facets of cosmological galaxy evolution.",
"doi": "10.1093/mnras/stx108",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-05",
"volume": "467",
"pages": "115-132"
},
{
"id": "authors:wk0fx-mdf75",
"collection": "authors",
"collection_id": "wk0fx-mdf75",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161107-114246249",
"type": "article",
"title": "The Structure and Dynamical Evolution of the Stellar Disk of a Simulated Milky Way-Mass Galaxy",
"author": [
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Wetzel",
"given_name": "Andrew R.",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Kirby",
"given_name": "Evan N.",
"orcid": "0000-0001-6196-5162",
"clpid": "Kirby-E-N"
},
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
}
],
"abstract": "We study the structure, age and metallicity gradients, and dynamical evolution using a cosmological zoom-in simulation of a Milky Way-mass galaxy from the Feedback in Realistic Environments project. In the simulation, stars older than 6 Gyr were formed in a chaotic, bursty mode and have the largest vertical scaleheights (1.5\u20132.5 kpc) by z = 0, while stars younger than 6 Gyr were formed in a relatively calm, stable disc. The vertical scaleheight increases with stellar age at all radii, because (1) stars that formed earlier were thicker 'at birth', and (2) stars were kinematically heated to an even thicker distribution after formation. Stars of the same age are thicker in the outer disc than in the inner disc (flaring). These lead to positive vertical age gradients and negative radial age gradients. The radial metallicity gradient is negative at the mid-plane, flattens at larger disc height |Z|, and turns positive above |Z| \u223c 1.5\u2009kpc. The vertical metallicity gradient is negative at all radii, but is steeper at smaller radii. These trends broadly agree with observations in the Milky Way and can be naturally understood from the age gradients. The vertical stellar density profile can be well described by two components, with scaleheights 200\u2013500 pc and 1\u20131.5 kpc, respectively. The thick component is a mix of stars older than 4 Gyr, which formed through a combination of several mechanisms. Our results also demonstrate that it is possible to form a thin disc in cosmological simulations even with a strong stellar feedback.",
"doi": "10.1093/mnras/stx273",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-05",
"series_number": "2",
"volume": "467",
"issue": "2",
"pages": "2430-2444"
},
{
"id": "authors:z7ftf-8qp06",
"collection": "authors",
"collection_id": "z7ftf-8qp06",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160202-071708669",
"type": "article",
"title": "An instability of feedback regulated star formation in galactic nuclei",
"author": [
{
"family_name": "Torrey",
"given_name": "Paul",
"orcid": "0000-0002-5653-0786",
"clpid": "Torrey-P"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Vogelsberger",
"given_name": "Mark",
"orcid": "0000-0001-8593-7692",
"clpid": "Vogelsberger-M"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N"
}
],
"abstract": "We examine the stability of feedback-regulated star formation (SF) in galactic nuclei and contrast it to SF in extended discs. In galactic nuclei the dynamical time becomes shorter than the time over which feedback from young stars evolves. We argue analytically that the balance between stellar feedback and gravity is unstable in this regime. We study this using numerical simulations with pc-scale resolution and explicit stellar feedback taken from stellar evolution models. The nuclear gas mass, young stellar mass, and SFR within the central ~100 pc (the short-timescale regime) never reach steady-state, but instead go through dramatic, oscillatory cycles. Stars form until a\ncritical surface density of young stars is present (such that feedback overwhelms gravity), at which point they begin to expel gas from the nucleus. Since the dynamical times are shorter than the stellar evolution times, the stars do not die as the gas is expelled, but continue to push, triggering a runaway quenching of star formation in the nucleus. However the expelled gas is largely not unbound from the galaxy, but goes into a galactic fountain which re-fills the nuclear region after the massive stars from the previous burst cycle have died off (~50 Myr timescale). On large scales (>1 kpc), the galaxy-scale gas content and SFR is more stable. We examine the consequences of this episodic nuclear star formation for the Kennicutt-Schmidt (KS) relation: while a tight KS relation exists on ~1 kpc scales in good agreement with observations, the scatter increases dramatically in smaller apertures centered on galactic nuclei.",
"doi": "10.1093/mnras/stx254",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-05",
"series_number": "2",
"volume": "467",
"issue": "2",
"pages": "2301-2314"
},
{
"id": "authors:c1n9m-0ew11",
"collection": "authors",
"collection_id": "c1n9m-0ew11",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170428-101904354",
"type": "article",
"title": "Scaling laws of passive-scalar diffusion in the interstellar medium",
"author": [
{
"family_name": "Colbrook",
"given_name": "Matthew J.",
"clpid": "Colbrook-M-J"
},
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Squire",
"given_name": "Jonathan",
"orcid": "0000-0001-8479-962X",
"clpid": "Squire-J"
}
],
"abstract": "Passive-scalar mixing (metals, molecules, etc.) in the turbulent interstellar medium (ISM) is critical for abundance patterns of stars and clusters, galaxy and star formation, and cooling from the circumgalactic medium. However, the fundamental scaling laws remain poorly understood in the highly supersonic, magnetized, shearing regime relevant for the ISM. We therefore study the full scaling laws governing passive-scalar transport in idealized simulations of supersonic turbulence. Using simple phenomenological arguments for the variation of diffusivity with scale based on Richardson diffusion, we propose a simple fractional diffusion equation to describe the turbulent advection of an initial passive scalar distribution. These predictions agree well with the measurements from simulations, and vary with turbulent Mach number in the expected manner, remaining valid even in the presence of a large-scale shear flow (e.g. rotation in a galactic disc). The evolution of the scalar distribution is not the same as obtained using simple, constant 'effective diffusivity' as in Smagorinsky models, because the scale dependence of turbulent transport means an initially Gaussian distribution quickly develops highly non-Gaussian tails. We also emphasize that these are mean scalings that apply only to ensemble behaviours (assuming many different, random scalar injection sites): individual Lagrangian 'patches' remain coherent (poorly mixed) and simply advect for a large number of turbulent flow-crossing times.",
"doi": "10.1093/mnras/stx261",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-05",
"series_number": "2",
"volume": "467",
"issue": "2",
"pages": "2421-2429"
},
{
"id": "authors:0nd4k-nbk65",
"collection": "authors",
"collection_id": "0nd4k-nbk65",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170623-110357171",
"type": "article",
"title": "Why do high-redshift galaxies show diverse gas-phase metallicity gradients?",
"author": [
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Torrey",
"given_name": "Paul",
"orcid": "0000-0002-5653-0786",
"clpid": "Torrey-P"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "Recent spatially resolved observations of galaxies at z \u223c 0.6\u20133 reveal that high-redshift galaxies show complex kinematics and a broad distribution of gas-phase metallicity gradients. To understand these results, we use a suite of high-resolution cosmological zoom-in simulations from the Feedback in Realistic Environments project, which include physically motivated models of the multiphase interstellar medium, star formation and stellar feedback. Our simulations reproduce the observed diversity of kinematic properties and metallicity gradients, broadly consistent with observations at z \u223c 0\u20133. Strong negative metallicity gradients only appear in galaxies with a rotating disc, but not all rotationally supported galaxies have significant gradients. Strongly perturbed galaxies with little rotation always have flat gradients. The kinematic properties and metallicity gradient of a high-redshift galaxy can vary significantly on short time-scales, associated with starburst episodes. Feedback from a starburst can destroy the gas disc, drive strong outflows and flatten a pre-existing negative metallicity gradient. The time variability of a single galaxy is statistically similar to the entire simulated sample, indicating that the observed metallicity gradients in high-redshift galaxies reflect the instantaneous state of the galaxy rather than the accretion and growth history on cosmological time-scales. We find weak dependence of metallicity gradient on stellar mass and specific star formation rate (sSFR). Low-mass galaxies and galaxies with high sSFR tend to have flat gradients, likely due to the fact that feedback is more efficient in these galaxies. We argue that it is important to resolve feedback on small scales in order to produce the diverse metallicity gradients observed.",
"doi": "10.1093/mnras/stx034",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-05",
"series_number": "4",
"volume": "466",
"issue": "4",
"pages": "4780-4794"
},
{
"id": "authors:2ys91-22309",
"collection": "authors",
"collection_id": "2ys91-22309",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160317-141936363",
"type": "article",
"title": "Anisotropic Diffusion in Mesh-Free Numerical Magnetohydrodynamics",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We extend recently developed mesh-free Lagrangian methods for numerical magnetohydrodynamics (MHD) to arbitrary anisotropic diffusion equations, including: passive scalar diffusion, Spitzer\u2013Braginskii conduction and viscosity, cosmic ray diffusion/streaming, anisotropic radiation transport, non-ideal MHD (Ohmic resistivity, ambipolar diffusion, the Hall effect) and turbulent 'eddy diffusion'. We study these as implemented in the code gizmo for both new meshless finite-volume Godunov schemes (MFM/MFV). We show that the MFM/MFV methods are accurate and stable even with noisy fields and irregular particle arrangements, and recover the correct behaviour even in arbitrarily anisotropic cases. They are competitive with state-of-the-art AMR/moving-mesh methods, and can correctly treat anisotropic diffusion-driven instabilities (e.g. the MTI and HBI, Hall MRI). We also develop a new scheme for stabilizing anisotropic tensor-valued fluxes with high-order gradient estimators and non-linear flux limiters, which is trivially generalized to AMR/moving-mesh codes. We also present applications of some of these improvements for SPH, in the form of a new integral-Godunov SPH formulation that adopts a moving-least squares gradient estimator and introduces a flux-limited Riemann problem between particles.",
"doi": "10.1093/mnras/stw3306",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-04",
"series_number": "3",
"volume": "466",
"issue": "3",
"pages": "3387-3405"
},
{
"id": "authors:cyg3h-fbw55",
"collection": "authors",
"collection_id": "cyg3h-fbw55",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170518-133304820",
"type": "article",
"title": "Supernovae, supercomputers, and galactic evolution",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "The stars in a galaxy emit radiation and solar winds, and they sometimes die in fantastic explosions. Supercomputer simulations are now beginning to assess how those energy releases affect the galaxy's life.",
"doi": "10.1063/PT.3.3533",
"issn": "0031-9228",
"publisher": "American Institute of Physics",
"publication": "Physics Today",
"publication_date": "2017-04",
"series_number": "4",
"volume": "70",
"issue": "4",
"pages": "70-71"
},
{
"id": "authors:er8ps-97x73",
"collection": "authors",
"collection_id": "er8ps-97x73",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170428-093947287",
"type": "article",
"title": "(Star)bursts of FIRE: observational signatures of bursty star formation in galaxies",
"author": [
{
"family_name": "Sparre",
"given_name": "Martin",
"orcid": "0000-0002-9735-3851",
"clpid": "Sparre-M"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Muratov",
"given_name": "Alexander L.",
"clpid": "Muratov-A-L"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Galaxy formation models are now able to reproduce observed relations such as the relation between galaxies' star formation rates (SFRs) and stellar masses (M^*) and the stellar-mass\u2013halo-mass relation. We demonstrate that comparisons of the short-time-scale variability in galaxy SFRs with observational data provide an additional useful constraint on the physics of galaxy formation feedback. We apply SFR indicators with different sensitivity time-scales to galaxies from the Feedback in Realistic Environments (FIRE) simulations. We find that the SFR\u2013M* relation has a significantly greater scatter when the H\u03b1-derived SFR is considered compared with when the far-ultraviolet (FUV)-based SFR is used. This difference is a direct consequence of bursty star formation because the FIRE galaxies exhibit order-of-magnitude SFR variations over time-scales of a few Myr. We show that the difference in the scatter between the simulated H\u03b1- and FUV-derived SFR\u2013M^* relations at z = 2 is consistent with observational constraints. We also find that the H\u03b1/FUV ratios predicted by the simulations at z = 0 are similar to those observed for local galaxies except for a population of low-mass (M* \u2272 10^(9.5)\u2009M_\u2299) simulated galaxies with lower H\u03b1/FUV ratios than observed. We suggest that future cosmological simulations should compare the H\u03b1/FUV ratios of their galaxies with observations to constrain the feedback models employed.",
"doi": "10.1093/mnras/stw3011",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-04",
"series_number": "1",
"volume": "466",
"issue": "1",
"pages": "88-104"
},
{
"id": "authors:fc1k0-ksa60",
"collection": "authors",
"collection_id": "fc1k0-ksa60",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161205-132716278",
"type": "article",
"title": "Giant clumps in the FIRE simulations: a case study of a massive high-redshift galaxy",
"author": [
{
"family_name": "Oklop\u010di\u0107",
"given_name": "Antonija",
"orcid": "0000-0002-9584-6476",
"clpid": "Oklop\u010di\u0107-A"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N"
}
],
"abstract": "The morphology of massive star-forming galaxies at high redshift is often dominated by giant clumps of mass ~ 10^8 - 10^9 M_\u2609 and size ~ 100 - 1000 pc. Previous studies have proposed that giant clumps might have an important role in the evolution of their host galaxy, particularly in building the central bulge. However, this depends on whether clumps live long enough to migrate from their original location in the disc or whether they get disrupted by their own stellar feedback before reaching the centre of the galaxy. We use cosmological hydrodynamical simulations from the FIRE (Feedback in Realistic Environments) project that implement explicit treatments of stellar feedback and ISM physics to study the properties of these clumps. We follow the evolution of giant clumps in a massive (M_* ~ 10^(10.8) M_\u2609 at z = 1), discy, gas-rich galaxy from redshift z \u2273 2 to z = 1. Even though the clumpy phase of this galaxy lasts over a gigayear, individual gas clumps are short-lived, with mean lifetime of massive clumps of ~ 20 Myr. During that time, they turn between 0.1% and 20% of their gas into stars before being disrupted, similar to local GMCs. Clumps with M \u2273 10^7 M_\u2609 account for ~ 20 % of the total star formation in the galaxy during the clumpy phase, producing ~ 10^(10) M_\u2609 of stars. We do not find evidence for net inward migration of clumps within the galaxy. The number of giant clumps and their mass decrease at lower redshifts, following the decrease in the overall gas fraction and star-formation rate.",
"doi": "10.1093/mnras/stw2754",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-02-11",
"series_number": "1",
"volume": "465",
"issue": "1",
"pages": "952-969"
},
{
"id": "authors:qktk7-dhw02",
"collection": "authors",
"collection_id": "qktk7-dhw02",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161128-095736863",
"type": "article",
"title": "ALMA Resolves the Nuclear Disks of Arp 220",
"author": [
{
"family_name": "Scoville",
"given_name": "Nick",
"orcid": "0000-0002-0438-3323",
"clpid": "Scoville-N-Z"
},
{
"family_name": "Murchikova",
"given_name": "Lena",
"orcid": "0000-0001-8986-5403",
"clpid": "Murchikova-Elena"
},
{
"family_name": "Walter",
"given_name": "Fabian",
"orcid": "0000-0003-4793-7880",
"clpid": "Walter-F"
},
{
"family_name": "Vlahakis",
"given_name": "Catherine",
"orcid": "0000-0003-3745-4228",
"clpid": "Vlahakis-Catherine"
},
{
"family_name": "Koda",
"given_name": "Jin",
"orcid": "0000-0002-8762-7863",
"clpid": "Koda-Jin"
},
{
"family_name": "Vanden Bout",
"given_name": "Paul A.",
"orcid": "0000-0003-3304-3974",
"clpid": "Vanden-Bout-Paul-A"
},
{
"family_name": "Barnes",
"given_name": "Joshua",
"clpid": "Barnes-Joshua"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
},
{
"family_name": "Sheth",
"given_name": "Kartik",
"orcid": "0000-0002-5496-4118",
"clpid": "Sheth-K"
},
{
"family_name": "Yun",
"given_name": "Min",
"orcid": "0000-0001-7095-7543",
"clpid": "Yun-Min-S"
},
{
"family_name": "Sanders",
"given_name": "David B.",
"orcid": "0000-0002-1233-9998",
"clpid": "Sanders-D-B"
},
{
"family_name": "Armus",
"given_name": "Lee",
"orcid": "0000-0003-3498-2973",
"clpid": "Armus-L"
},
{
"family_name": "Cox",
"given_name": "Pierre",
"orcid": "0000-0003-2027-8221",
"clpid": "Cox-Pierre"
},
{
"family_name": "Thompson",
"given_name": "Todd",
"clpid": "Thompson-T-A"
},
{
"family_name": "Robertson",
"given_name": "Brant",
"orcid": "0000-0002-4271-0364",
"clpid": "Robertson-B-E"
},
{
"family_name": "Zschaechner",
"given_name": "Laura",
"orcid": "0000-0002-9919-8672",
"clpid": "Zschaechner-L-K"
},
{
"family_name": "Tacconi",
"given_name": "Linda",
"orcid": "0000-0002-1485-9401",
"clpid": "Tacconi-Linda-J"
},
{
"family_name": "Torrey",
"given_name": "Paul",
"orcid": "0000-0002-5653-0786",
"clpid": "Torrey-P"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Genzel",
"given_name": "Reinhard",
"orcid": "0000-0002-2767-9653",
"clpid": "Genzel-R"
},
{
"family_name": "Hopkins",
"given_name": "Phil",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "van der Werf",
"given_name": "Paul",
"orcid": "0000-0001-5434-5942",
"clpid": "van-der-Werf-P-P"
},
{
"family_name": "Decarli",
"given_name": "Roberto",
"orcid": "0000-0002-2662-8803",
"clpid": "Decarli-R"
}
],
"abstract": "We present 90 mas (37 pc) resolution ALMA imaging of Arp 220 in the CO (1-0) line and continuum at \u03bb = 2.6 mm. The internal gas distribution and kinematics of both galactic nuclei are well resolved for the first time. In the west nucleus, the major gas and dust emission extends out to 0.\"2 radius (74 pc); the central resolution element shows a strong peak in the dust emission but a factor of 3 dip in the CO line emission. In this nucleus, the dust is apparently optically thick (\u03c4_(2.6 mm) ~ 1) at \u03bb = 2.6 mm with a dust brightness temperature of ~147 K. The column of interstellar matter at this nucleus is N_(H2) \u2a7e 2 x 10^(26)cm^(\u22122), corresponding to ~900 gr cm^(\u22122). The east nucleus is more elongated with radial extent 0.\"3 or ~111 pc. The derived kinematics of the nuclear disks provide a good fit to the line profiles, yielding the emissivity distributions, the rotation curves, and velocity dispersions. In the west nucleus, there is evidence of a central Keplerian component requiring a central mass of 8 \u00d7 10^8 M\u2299. The intrinsic widths of the emission lines are \u0394\u03bd(FWHM) = 250 (west) and 120 (east) km s^(\u22121). Given the very short dissipation timescales for turbulence (\u227e10^5 years), we suggest that the line widths may be due to semicoherent motions within the nuclear disks. The symmetry of the nuclear disk structures is impressive, implying the merger timescale is significantly longer than the rotation period of the disks.",
"doi": "10.3847/1538-4357/836/1/66",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2017-02-10",
"series_number": "1",
"volume": "836",
"issue": "1",
"pages": "Art. No. 66"
},
{
"id": "authors:p7djw-np054",
"collection": "authors",
"collection_id": "p7djw-np054",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170126-160443858",
"type": "article",
"title": "Are the Formation and Abundances of Metal-poor Stars the Result of Dust Dynamics?",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Conroy",
"given_name": "Charlie",
"orcid": "0000-0002-1590-8551",
"clpid": "Conroy-C"
}
],
"abstract": "Large dust grains can fluctuate dramatically in their local density, relative to the gas, in neutral turbulent disks. Small, high-redshift galaxies (before reionization) represent ideal environments for this process. We show via simple arguments and simulations that order-of-magnitude fluctuations are expected in local abundances of large grains (>100 \u00c5) under these conditions. This can have important consequences for star formation and stellar metal abundances in extremely metal-poor stars. Low-mass stars can form in dust-enhanced regions almost immediately after some dust forms even if the galaxy-average metallicity is too low for fragmentation to occur. We argue that the metal abundances of these \"promoted\" stars may contain interesting signatures as the CNO abundances (concentrated in large carbonaceous grains and ices) and Mg and Si (in large silicate grains) can be enhanced and/or fluctuate almost independently. Remarkably, the otherwise puzzling abundance patterns of some metal-poor stars can be well fit by standard IMF-averaged core-collapse SNe yields if we allow for fluctuating local dust-to-gas ratios. We also show that the observed log-normal distribution of enhancements in these species agrees with our simulations. Moreover, we confirm that Mg and Si are correlated in these stars; the abundance ratios are similar to those in local silicate grains. Meanwhile [Mg/Ca], predicted to be nearly invariant from pure SNe yields, shows very large enhancements and variations up to factors of \u2273100 as expected in the dust-promoted model, preferentially in the [C/Fe]-enhanced metal-poor stars. Together, this suggests that (1) dust exists in second-generation star formation, (2) local dust-to-gas ratio fluctuations occur in protogalaxies and can be important for star formation, and (3) the light element abundances of these stars may be affected by the local chemistry of dust where they formed, rather than directly tracing nucleosynthesis from earlier populations.",
"doi": "10.3847/1538-4357/835/2/154",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2017-02-01",
"series_number": "2",
"volume": "835",
"issue": "2",
"pages": "Art. No. 154"
},
{
"id": "authors:sxnhn-t2w47",
"collection": "authors",
"collection_id": "sxnhn-t2w47",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170616-094907367",
"type": "article",
"title": "When the Jeans do not Fit: How Stellar Feedback Drives Stellar Kinematics and Complicates Dynamical Modeling in Low-mass Galaxies",
"author": [
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Wetzel",
"given_name": "Andrew R.",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Geha",
"given_name": "Marla",
"orcid": "0000-0002-7007-9725",
"clpid": "Geha-Marla-C"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
}
],
"abstract": "In low-mass galaxies, stellar feedback can drive gas outflows that generate non-equilibrium fluctuations in the gravitational potential. Using cosmological zoom-in baryonic simulations from the Feedback in Realistic Environments project, we investigate how these fluctuations affect stellar kinematics and the reliability of Jeans dynamical modeling in low-mass galaxies. We find that stellar velocity dispersion and anisotropy profiles fluctuate significantly over the course of galaxies' starburst cycles. We therefore predict an observable correlation between star formation rate and stellar kinematics: dwarf galaxies with higher recent star formation rates should have systemically higher stellar velocity dispersions. This prediction provides an observational test of the role of stellar feedback in regulating both stellar and dark-matter densities in dwarf galaxies. We find that Jeans modeling, which treats galaxies as virialized systems in dynamical equilibrium, overestimates a galaxy's dynamical mass during periods of post-starburst gas outflow and underestimates it during periods of net inflow. Short-timescale potential fluctuations lead to typical errors of ~20% in dynamical mass estimates, even if full three-dimensional stellar kinematics\u2014including the orbital anisotropy\u2014are known exactly. When orbital anisotropy is not known a priori, typical mass errors arising from non-equilibrium fluctuations in the potential are larger than those arising from the mass-anisotropy degeneracy. However, Jeans modeling alone cannot reliably constrain the orbital anisotropy, and problematically, it often favors anisotropy models that do not reflect the true profile. If galaxies completely lose their gas and cease forming stars, fluctuations in the potential subside, and Jeans modeling becomes much more reliable.",
"doi": "10.3847/1538-4357/835/2/193",
"issn": "1538-4357",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2017-02-01",
"series_number": "2",
"volume": "835",
"issue": "2",
"pages": "Art. No. 193"
},
{
"id": "authors:j69ek-5j328",
"collection": "authors",
"collection_id": "j69ek-5j328",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160301-105518286",
"type": "article",
"title": "How stellar feedback simultaneously regulates star formation and drives outflows",
"author": [
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We present an analytic model for how momentum deposition from stellar feedback simultaneously regulates star formation and drives outflows in a turbulent interstellar medium (ISM). Because the ISM is turbulent, a given patch of ISM exhibits sub-patches with a range of surface densities. The high-density patches are 'pushed' by feedback, thereby driving turbulence and self-regulating local star formation. Sufficiently low-density patches, however, are accelerated to above the escape velocity before the region can self-adjust and are thus vented as outflows. When the gas fraction is \u2273 0.3, the ratio of the turbulent velocity dispersion to the circular velocity is sufficiently high that at any given time, of the order of half of the ISM has surface density less than the critical value and thus can be blown out on a dynamical time. The resulting outflows have a mass-loading factor (\u03b7\u2261M_(out)/M_\u22c6) that is inversely proportional to the gas fraction times the circular velocity. At low gas fractions, the star formation rate needed for local self-regulation, and corresponding turbulent Mach number, declines rapidly; the ISM is 'smoother', and it is actually more difficult to drive winds with large mass-loading factors. Crucially, our model predicts that stellar-feedback-driven outflows should be suppressed at z\u22721 in M_\u22c6\u227310^(10)M_\u2299 galaxies. This mechanism allows massive galaxies to exhibit violent outflows at high redshifts and then 'shut down' those outflows at late times, thereby enabling the formation of a smooth, extended thin stellar disc. We provide simple fitting functions for \u03b7 that should be useful for sub-resolution and semi-analytic models.",
"doi": "10.1093/mnras/stw2888",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-02",
"series_number": "2",
"volume": "465",
"issue": "2",
"pages": "1682-1698"
},
{
"id": "authors:v9efw-azz33",
"collection": "authors",
"collection_id": "v9efw-azz33",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151118-080725780",
"type": "article",
"title": "The no-spin zone: rotation vs dispersion support in observed and simulated dwarf galaxies",
"author": [
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-C"
},
{
"family_name": "Pace",
"given_name": "Andrew B.",
"orcid": "0000-0002-6021-8760",
"clpid": "Pace-A-B"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-J-S"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "O\u00f1orbe",
"given_name": "Jos\u00e9",
"clpid": "O\u00f1orbe-J"
},
{
"family_name": "Fitts",
"given_name": "Alex",
"orcid": "0000-0002-8928-6011",
"clpid": "Fitts-A"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "We perform a systematic Bayesian analysis of rotation vs. dispersion support (v_(rot)/\u03c3) in 40 dwarf galaxies throughout the Local Volume (LV) over a stellar mass range 10^(3.5) M_\u2299 < M\u22c6 < 10^8 M_\u2299. We find that the stars in \u223c90% of the LV dwarf galaxies studied -- both satellites and isolated systems -- are dispersion-supported. In particular, we show that 7/10 *isolated* dwarfs in our sample have stellar populations with v_(rot)/\u03c3<0.6. All have v_(rot)/\u03c3\u22722. These results challenge the traditional view that the stars in gas-rich dwarf irregulars (dIrrs) are distributed in cold, rotationally-supported stellar disks, while gas-poor dwarf spheroidals (dSphs) are kinematically distinct in having dispersion-supported stars. We see no clear trend between v_(rot)/\u03c3 and distance to the closest L\u22c6 galaxy, nor between v_(rot)/\u03c3 and M\u22c6 within our mass range. We apply the same Bayesian analysis to four FIRE hydrodynamic zoom-in simulations of isolated dwarf galaxies (10^9M\u2299",
"doi": "10.1093/mnras/stw2583",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-02",
"series_number": "2",
"volume": "465",
"issue": "2",
"pages": "2420-2431"
},
{
"id": "authors:gw0h1-ae070",
"collection": "authors",
"collection_id": "gw0h1-ae070",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160404-145148034",
"type": "article",
"title": "Gravitational torque-driven black hole growth and feedback in cosmological simulations",
"author": [
{
"family_name": "Angl\u00e9s-Alc\u00e1zar",
"given_name": "Daniel",
"orcid": "0000-0001-5769-4945",
"clpid": "Angl\u00e9s-Alc\u00e1zar-D"
},
{
"family_name": "Dav\u00e9",
"given_name": "Romeel",
"clpid": "Dav\u00e9-R"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "\u00d6zel",
"given_name": "Feryal",
"clpid": "\u00d6zel-F"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We investigate black hole\u2013host galaxy scaling relations in cosmological simulations with a self-consistent black hole growth and feedback model. Our sub-grid accretion model captures the key scalings governing angular momentum transport by gravitational torques from galactic scales down to parsec scales, while our kinetic feedback implementation enables the injection of outflows with properties chosen to match observed nuclear outflows (star formation-driven winds are not included to isolate the effects of black hole feedback). We show that 'quasar mode' feedback can have a large impact on the thermal properties of the intergalactic medium and the growth of galaxies and massive black holes for kinetic feedback efficiencies as low as 0.1 per cent relative to the bolometric luminosity. None the less, our simulations indicate that the black hole\u2013host scaling relations are only weakly dependent on the effects of black hole feedback on galactic scales, since black hole feedback suppresses the growth of galaxies and massive black holes by a similar amount. In contrast, the rate at which gravitational torques feed the central black hole relative to the host galaxy star formation rate governs the slope and normalization of the black hole\u2013host correlations. Our results suggest that a common gas supply regulated by gravitational torques is the primary driver of the observed co-evolution of black holes and galaxies.",
"doi": "10.1093/mnras/stw2565",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2017-01",
"series_number": "3",
"volume": "464",
"issue": "3",
"pages": "2840-2853"
},
{
"id": "authors:03zyv-3mg03",
"collection": "authors",
"collection_id": "03zyv-3mg03",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161219-102104799",
"type": "article",
"title": "The AGORA High-resolution Galaxy Simulations Comparison Project. II. Isolated Disk Test",
"author": [
{
"family_name": "Kim",
"given_name": "Ji-hoon",
"orcid": "0000-0003-4464-1160",
"clpid": "Kim-Ji-hoon"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hummels",
"given_name": "Cameron B.",
"orcid": "0000-0002-3817-8133",
"clpid": "Hummels-C-B"
},
{
"literal": "AGORA Collaboration"
}
],
"abstract": "Using an isolated Milky Way-mass galaxy simulation, we compare results from nine state-of-the-art gravito-hydrodynamics codes widely used in the numerical community. We utilize the infrastructure we have built for the AGORA High-resolution Galaxy Simulations Comparison Project. This includes the common disk initial conditions, common physics models (e.g., radiative cooling and UV background by the standardized package Grackle) and common analysis toolkit yt, all of which are publicly available. Subgrid physics models such as Jeans pressure floor, star formation, supernova feedback energy, and metal production are carefully constrained across code platforms. With numerical accuracy that resolves the disk scale height, we find that the codes overall agree well with one another in many dimensions including: gas and stellar surface densities, rotation curves, velocity dispersions, density and temperature distribution functions, disk vertical heights, stellar clumps, star formation rates, and Kennicutt\u2013Schmidt relations. Quantities such as velocity dispersions are very robust (agreement within a few tens of percent at all radii) while measures like newly formed stellar clump mass functions show more significant variation (difference by up to a factor of ~3). Systematic differences exist, for example, between mesh-based and particle-based codes in the low-density region, and between more diffusive and less diffusive schemes in the high-density tail of the density distribution. Yet intrinsic code differences are generally small compared to the variations in numerical implementations of the common subgrid physics such as supernova feedback. Our experiment reassures that, if adequately designed in accordance with our proposed common parameters, results of a modern high-resolution galaxy formation simulation are more sensitive to input physics than to intrinsic differences in numerical schemes.",
"doi": "10.3847/1538-4357/833/2/202",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2016-12-20",
"series_number": "2",
"volume": "833",
"issue": "2",
"pages": "Art. No. 202"
},
{
"id": "authors:nszsw-zyh50",
"collection": "authors",
"collection_id": "nszsw-zyh50",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170310-124122492",
"type": "article",
"title": "The impact of stellar feedback on hot gas in galaxy haloes: the Sunyaev\u2013Zel'dovich effect and soft X-ray emission",
"author": [
{
"family_name": "van de Voort",
"given_name": "Freeke",
"orcid": "0000-0002-6301-638X",
"clpid": "van-de-Voort-Freeke"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-Robert"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Hafen",
"given_name": "Zachary",
"orcid": "0000-0001-7326-1736",
"clpid": "Hafen-Zachary-H"
}
],
"abstract": "The thermal Sunyaev\u2013Zel'dovich (SZ) effect and soft X-ray emission are routinely observed around massive galaxies and in galaxy groups and clusters. We study these observational diagnostics of galaxy haloes for a suite of cosmological 'zoom-in' simulations from the 'Feedback In Realistic Environments' project, which spans a large range in halo mass (10^(10\u201313)\u2009M_\u2299). We explore the effect of stellar feedback on the hot gas observables. The properties of our simulated groups, such as baryon fractions, SZ flux, and X-ray luminosities (LX), are broadly consistent with existing observations, even though feedback from active galactic nuclei is not included. We make predictions for future observations of lower mass objects for both SZ and diffuse X-ray measurements, finding that they are not just scaled-down versions of massive galaxies, but more strongly affected by galactic winds driven by star formation. Low-mass haloes (\u2272 10^(11)\u2009M_\u2299) retain a low fraction of their baryons, which results in a strong suppression of the SZ signal. Our simulations therefore predict a scaling with halo mass that is steeper than self-similar for haloes less massive than 10^(13)\u2009M_\u2299. For halo masses \u2272 10^(12)\u2009M_\u2299, LX is time variable and correlated primarily with the star formation rate (SFR). For these objects, the diffuse X-ray emission is powered mostly by galactic winds and the gas dominating the X-ray emission is flowing out with radial velocities close to the halo's circular velocity. For halo masses \u2273 10^(13)\u2009M_\u2299, on the other hand, LX is much less variable and not correlated with the SFR, because the emission originates from the quasi-hydrostatic, virialized halo gas.",
"doi": "10.1093/mnras/stw2322",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2016-12",
"series_number": "4",
"volume": "463",
"issue": "4",
"pages": "4533-4544"
},
{
"id": "authors:3epfn-dyc23",
"collection": "authors",
"collection_id": "3epfn-dyc23",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161031-112035738",
"type": "article",
"title": "When and where did GW150914 form?",
"author": [
{
"family_name": "Lamberts",
"given_name": "A.",
"orcid": "0000-0001-8740-0127",
"clpid": "Lamberts-A"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "S.",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Clausen",
"given_name": "D. R.",
"clpid": "Clausen-D-R"
},
{
"family_name": "Hopkins",
"given_name": "P. F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "The recent LIGO detection of gravitational waves (GW150914), likely originating from the merger of two \u223c 30M_\u2299 black holes suggests progenitor stars of low metallicity ([Z/Z_\u2299] \u2272 0.3), constraining when and where the progenitor of GW150914 may have formed. We combine estimates of galaxy properties (star-forming gas metallicity, star formation rate and merger rate) across cosmic time to predict the low redshift black hole \u2013 black hole merger rate as a function of present day host galaxy mass, M_(gal), the formation redshift of the progenitor system z_f and different progenitor metallicities Z_p. For Z_p \u2a7e 0.1Z_\u2299, the signal is dominated by binaries in massive galaxies with z_f \u2243 2 while below Z_p \u2a7d 0.1Z_\u2299 most mergers come from binaries formed around z_f \u2243 0.5 in dwarf galaxies. Additional gravitational wave detections from merging massive black holes will provide constraints on the mass\u2013metallicity relation and massive star formation at high redshifts.",
"doi": "10.1093/mnrasl/slw152",
"issn": "1745-3925",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society: Letters",
"publication_date": "2016-11-21",
"series_number": "1",
"volume": "463",
"issue": "1",
"pages": "L31-L35"
},
{
"id": "authors:0zsqg-6ap93",
"collection": "authors",
"collection_id": "0zsqg-6ap93",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161128-151737516",
"type": "article",
"title": "Strongly time-variable ultraviolet metal-line emission from the circum-galactic medium of high-redshift galaxies",
"author": [
{
"family_name": "Sravan",
"given_name": "Niharika",
"clpid": "Sravan-N"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "van de Voort",
"given_name": "Freeke",
"orcid": "0000-0002-6301-638X",
"clpid": "van-de-Voort-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Muratov",
"given_name": "Alexander L.",
"clpid": "Muratov-A-L"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N"
}
],
"abstract": "We use cosmological simulations from the Feedback In Realistic Environments project, which implement a comprehensive set of stellar feedback processes, to study ultraviolet (UV) metal-line emission from the circum-galactic medium of high-redshift (z = 2\u20134) galaxies. Our simulations cover the halo mass range M_h \u223c 2 \u00d7 10^(11)\u20138.5 \u00d7 10^(12) M_\u2299 at z = 2, representative of Lyman break galaxies. Of the transitions we analyse, the low-ionization C\u2009iii (977 \u00c5) and Si\u2009iii (1207 \u00c5) emission lines are the most luminous, with C\u2009iv (1548 \u00c5) and Si\u2009iv (1394 \u00c5) also showing interesting spatially extended structures. The more massive haloes are on average more UV-luminous. The UV metal-line emission from galactic haloes in our simulations arises primarily from collisionally ionized gas and is strongly time variable, with peak-to-trough variations of up to \u223c2 dex. The peaks of UV metal-line luminosity correspond closely to massive and energetic mass outflow events, which follow bursts of star formation and inject sufficient energy into galactic haloes to power the metal-line emission. The strong time variability implies that even some relatively low-mass haloes may be detectable. Conversely, flux-limited samples will be biased towards haloes whose central galaxy has recently experienced a strong burst of star formation. Spatially extended UV metal-line emission around high-redshift galaxies should be detectable by current and upcoming integral field spectrographs such as the Multi Unit Spectroscopic Explorer on the Very Large Telescope and Keck Cosmic Web Imager.",
"doi": "10.1093/mnras/stw1962",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2016-11-21",
"series_number": "1",
"volume": "463",
"issue": "1",
"pages": "120-133"
},
{
"id": "authors:z59cm-mkk12",
"collection": "authors",
"collection_id": "z59cm-mkk12",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151022-135013652",
"type": "article",
"title": "A Constrained-Gradient Method to Control Divergence Errors in Numerical MHD",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "In numerical magnetohydrodynamics (MHD), a major challenge is maintaining \u2207\u22c5B=0. Constrained transport (CT) schemes achieve this but have been restricted to specific methods. For more general (meshless, moving-mesh, ALE) methods, 'divergence-cleaning' schemes reduce the \u2207\u22c5B errors; however they can still be significant and can lead to systematic errors which converge away slowly. We propose a new constrained gradient (CG) scheme which augments these with a projection step, and can be applied to any numerical scheme with a reconstruction. This iteratively approximates the least-squares minimizing, globally divergence-free reconstruction of the fluid. Unlike 'locally divergence free' methods, this actually minimizes the numerically unstable \u2207\u22c5B terms, without affecting the convergence order of the method. We implement this in the mesh-free code gizmo and compare various test problems. Compared to cleaning schemes, our CG method reduces the maximum \u2207\u22c5B errors by \u223c1\u20133 orders of magnitude (\u223c2\u20135 dex below typical errors if no \u2207\u22c5B cleaning is used). By preventing large \u2207\u22c5B at discontinuities, this eliminates systematic errors at jumps. Our CG results are comparable to CT methods; for practical purposes, the \u2207\u22c5B errors are eliminated. The cost is modest, \u223c30\u2009per\u2009cent of the hydro algorithm, and the CG correction can be implemented in a range of numerical MHD methods. While for many problems, we find Dedner-type cleaning schemes are sufficient for good results, we identify a range of problems where using only Powell or '8-wave' cleaning can produce order-of-magnitude errors.",
"doi": "10.1093/mnras/stw1578",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2016-10-11",
"series_number": "1",
"volume": "462",
"issue": "1",
"pages": "576-587"
},
{
"id": "authors:2nvsq-kdd09",
"collection": "authors",
"collection_id": "2nvsq-kdd09",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160202-075033622",
"type": "article",
"title": "A Stellar Feedback Origin for Neutral Hydrogen in High-Redshift Quasar-Mass Halos",
"author": [
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N"
}
],
"abstract": "Observations of quasar pairs reveal that quasar host halos at z ~ 2 have large covering fractions of cool dense gas (\u2273 60% for Lyman limit systems within a projected virial\nradius). Most simulations have so far failed to explain these large observed covering fractions. We analyze a new set of 15 simulated massive halos with explicit stellar\nfeedback from the FIRE project, covering the halo mass range M_h \u2248 2 x 10^(12) - 10^(13) M_\u2609 at z = 2. This extends our previous analysis of the circum-galactic medium of high-redshift galaxies to more massive halos. Feedback from active galactic nuclei (AGN) is not included in these simulations. We find covering fractions consistent with\nthose observed around z ~ 2 quasars. The large HI covering fractions arise from star formation-driven galactic winds, including winds from low-mass satellite galaxies that\ninteract with the cosmological infalling filaments in which they are typically embedded. The simulated covering fractions increase with both halo mass and redshift over\nthe ranges covered, as well as with resolution. Our simulations predict that galaxies occupying dark matter halos of mass similar to quasars but without a luminous\nAGN should have Lyman limit system covering fractions comparable to quasars. This prediction can be tested by measuring covering fractions transverse to sub-millimeter\ngalaxies or to more quiescent galaxies selected based on their high stellar mass.",
"doi": "10.1093/mnrasl/slw091",
"issn": "1745-3933",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society: Letters",
"publication_date": "2016-09-01",
"series_number": "1",
"volume": "461",
"issue": "1",
"pages": "L32-L36"
},
{
"id": "authors:esr2t-q9m88",
"collection": "authors",
"collection_id": "esr2t-q9m88",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160906-220609945",
"type": "article",
"title": "Reconciling Dwarf Galaxies with \u039bCDM Cosmology: Simulating A Realistic Population of Satellites Around a Milky Way-Mass Galaxy",
"author": [
{
"family_name": "Wetzel",
"given_name": "Andrew R.",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-A-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kim",
"given_name": "Ji-Hoon",
"clpid": "Kim-Ji-Hoon"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
}
],
"abstract": "Low-mass \"dwarf\" galaxies represent the most significant challenges to the cold dark matter (CDM) model of cosmological structure formation. Because these faint galaxies are (best) observed within the Local Group (LG) of the Milky Way (MW) and Andromeda (M31), understanding their formation in such an environment is critical. We present first results from the Latte Project: the Milky Way on Feedback in Realistic Environments (FIRE). This simulation models the formation of an MW-mass galaxy to z = 0 within \u039bCDM cosmology, including dark matter, gas, and stars at unprecedented resolution: baryon particle mass of 7070 M_\u2299 with gas kernel/softening that adapts down to 1 pc (with a median of 2-60 pc at z = 0). Latte was simulated using the GIZMO code with a mesh-free method for accurate hydrodynamics and the FIRE-2 model for star formation and explicit feedback within a multi-phase interstellar medium. For the first time, Latte self-consistently resolves the spatial scales corresponding to half-light radii of dwarf galaxies that form around an MW-mass host down to M_(star) \u2273 10^5 M_\u2299. Latte's population of dwarf galaxies agrees with the LG across a broad range of properties: (1) distributions of stellar masses and stellar velocity dispersions (dynamical masses), including their joint relation; (2) the mass\u2013metallicity relation; and (3) diverse range of star formation histories, including their mass dependence. Thus, Latte produces a realistic population of dwarf galaxies at M_(star) \u2273 10^5 M_\u2299 that does not suffer from the \"missing satellites\" or \"too big to fail\" problems of small-scale structure formation. We conclude that baryonic physics can reconcile observed dwarf galaxies with standard \u039bCDM cosmology.",
"doi": "10.3847/2041-8205/827/2/L23",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2016-08-20",
"series_number": "2",
"volume": "827",
"issue": "2",
"pages": "Art. No. L23"
},
{
"id": "authors:t9h26-8nr78",
"collection": "authors",
"collection_id": "t9h26-8nr78",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161028-070812816",
"type": "article",
"title": "mufasa: galaxy formation simulations with meshless hydrodynamics",
"author": [
{
"family_name": "Dav\u00e9",
"given_name": "Romeel",
"clpid": "Dav\u00e9-R"
},
{
"family_name": "Thompson",
"given_name": "Robert",
"clpid": "Thompson-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We present the mufasa suite of cosmological hydrodynamic simulations, which employs the gizmo meshless finite mass (MFM) code including H_2-based star formation, nine-element chemical evolution, two-phase kinetic outflows following scalings from the Feedback in Realistic Environments zoom simulations, and evolving halo mass-based quenching. Our fiducial (50\u2009h^(\u22121)\u2009Mpc)^3 volume is evolved to z = 0 with a quarter billion elements. The predicted galaxy stellar mass functions (GSMFs) reproduces observations from z = 4 \u2192 0 to \u2272 1.2\u03c3 in cosmic variance, providing an unprecedented match to this key diagnostic. The cosmic star formation history and stellar mass growth show general agreement with data, with a strong archaeological downsizing trend such that dwarf galaxies form the majority of their stars after z \u223c 1. We run 25 and 12.5\u2009h^(\u22121)\u2009Mpc volumes to z = 2 with identical feedback prescriptions, the latter resolving all hydrogen-cooling haloes, and the three runs display fair resolution convergence. The specific star formation rates broadly agree with data at z = 0, but are underpredicted at z \u223c 2 by a factor of 3, re-emphasizing a longstanding puzzle in galaxy evolution models. We compare runs using MFM and two flavours of smoothed particle hydrodynamics, and show that the GSMF is sensitive to hydrodynamics methodology at the \u223c\u00d72 level, which is sub-dominant to choices for parametrizing feedback.",
"doi": "10.1093/mnras/stw1862",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2016-07-30",
"series_number": "3",
"volume": "462",
"issue": "3",
"pages": "3265-3284"
},
{
"id": "authors:6x489-bcd56",
"collection": "authors",
"collection_id": "6x489-bcd56",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160202-084712784",
"type": "article",
"title": "Binary Stars Can Provide the \"Missing Photons\" Needed for Reionization",
"author": [
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kasen",
"given_name": "Daniel",
"clpid": "Kasen-D"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
}
],
"abstract": "Empirical constraints on reionization require galactic ionizing photon escape fractions f_(esc) \u2273 20\u2009per\u2009cent, but recent high-resolution radiation-hydrodynamic calculations have consistently found much lower values \u223c1\u20135\u2009per\u2009cent. While these models include strong stellar feedback and additional processes such as runaway stars, they almost exclusively consider stellar evolution models based on single (isolated) stars, despite the fact that most massive stars are in binaries. We re-visit these calculations, combining radiative transfer and high-resolution cosmological simulations with detailed models for stellar feedback from the Feedback in Realistic Environments project. For the first time, we use a stellar evolution model that includes a physically and observationally motivated treatment of binaries (the Binary Population and Spectral Synthesis model). Binary mass transfer and mergers enhance the population of massive stars at late times (\u22733\u2009Myr) after star formation, which in turn strongly enhances the late-time ionizing photon production (especially at low metallicities). These photons are produced after feedback from massive stars has carved escape channels in the interstellar medium, and so efficiently leak out of galaxies. As a result, the time-averaged 'effective' escape fraction (ratio of escaped ionizing photons to observed 1500\u2009\u00c5 photons) increases by factors \u223c4\u201310, sufficient to explain reionization. While important uncertainties remain, we conclude that binary evolution may be critical for understanding the ionization of the Universe.",
"doi": "10.1093/mnras/stw941",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2016-07-11",
"series_number": "4",
"volume": "459",
"issue": "4",
"pages": "3614-3619"
},
{
"id": "authors:m8zbg-qcr39",
"collection": "authors",
"collection_id": "m8zbg-qcr39",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150812-101357981",
"type": "article",
"title": "Star formation in a turbulent framework: from giant molecular clouds to protostars",
"author": [
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Turbulence is thought to be a primary driving force behind the early stages of star formation. In this framework large, self-gravitating, turbulent clouds fragment into smaller clouds which in turn fragment into even smaller ones. At the end of this cascade we find the clouds which collapse into protostars. Following this process is extremely challenging numerically due to the large dynamical range, so in this paper we propose a semi-analytic framework which is able to model star formation from the largest, giant molecular cloud scale, to the final protostellar size scale. Because of the simplicity of the framework it is ideal for theoretical experimentation to explore the principal processes behind different aspects of star formation, at the cost of introducing strong assumptions about the collapse process. The basic version of the model discussed in this paper only contains turbulence, gravity and crude assumptions about feedback; nevertheless it can reproduce the observed core mass function and provide the protostellar system mass function (PSMF), which shows a striking resemblance to the observed initial mass function (IMF), if a non-negligible fraction of gravitational energy goes into turbulence. Furthermore we find that to produce a universal IMF protostellar feedback must be taken into account otherwise the PSMF peak shows a strong dependence on the background temperature.",
"doi": "10.1093/mnras/stw619",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2016-06-11",
"series_number": "1",
"volume": "459",
"issue": "1",
"pages": "9-20"
},
{
"id": "authors:1s8bz-6ve36",
"collection": "authors",
"collection_id": "1s8bz-6ve36",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160512-111526655",
"type": "article",
"title": "The formation of massive, quiescent galaxies at cosmic noon",
"author": [
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "The cosmic noon (z \u223c 1.5\u20133) marked a period of vigorous star formation for most galaxies. However, about a third of the more massive galaxies at those times were quiescent in the sense that their observed stellar populations are inconsistent with rapid star formation. The reduced star formation activity is often attributed to gaseous outflows driven by feedback from supermassive black holes, but the impact of black hole feedback on galaxies in the young Universe is not yet definitively established. We analyse the origin of quiescent galaxies with the help of ultrahigh resolution, cosmological simulations that include feedback from stars but do not model the uncertain consequences of black hole feedback. We show that dark matter haloes with specific accretion rates below \u223c0.25\u20130.4 Gyr^(\u22121) preferentially host galaxies with reduced star formation rates and red broad-band colours. The fraction of such haloes in large dark matter only simulations matches the observed fraction of massive quiescent galaxies (\u223c10^(10)\u201310^(11)\u2009M\u2299). This strongly suggests that halo accretion rate is the key parameter determining which massive galaxies at z \u223c 1.5\u20133 become quiescent. Empirical models that connect galaxy and halo evolution, such as halo occupation distribution or abundance matching models, assume a tight link between galaxy properties and the masses of their parent haloes. These models will benefit from adding the specific accretion rate of haloes as a second model parameter.",
"doi": "10.1093/mnrasl/slw014",
"issn": "1745-3925",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society: Letters",
"publication_date": "2016-05-01",
"series_number": "1",
"volume": "458",
"issue": "1",
"pages": "L14-L18"
},
{
"id": "authors:v2xpq-bdk82",
"collection": "authors",
"collection_id": "v2xpq-bdk82",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150422-112435004",
"type": "article",
"title": "Stellar and Quasar Feedback in Concert: Effects on AGN Accretion, Obscuration, and Outflows",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Torrey",
"given_name": "Paul",
"orcid": "0000-0002-5653-0786",
"clpid": "Torrey-P"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N"
}
],
"abstract": "We study the interaction of feedback from active galactic nuclei (AGN) and a multiphase interstellar medium (ISM), in simulations including explicit stellar feedback, multiphase cooling, accretion-disc winds, and Compton heating. We examine radii \u223c0.1\u2013100\u2009pc around a black hole (BH), where the accretion rate on to the BH is determined and where AGN-powered winds and radiation couple to the ISM. We conclude: (1) the BH accretion rate is determined by exchange of angular momentum between gas and stars in gravitational instabilities. This produces accretion rates \u223c0.03\u20131\u2009M_\u2299\u2009yr^(\u22121), sufficient to power luminous AGN. (2) The gas disc in the galactic nucleus undergoes an initial burst of star formation followed by several million years where stellar feedback suppresses the star formation rate (SFR). (3) AGN winds injected at small radii with momentum fluxes \u223cL_(AGN)/c couple efficiently to the ISM and have dramatic effects on ISM properties within \u223c100\u2009pc. AGN winds suppress the nuclear SFR by factors \u223c10\u201330 and BH accretion rate by factors \u223c3\u201330. They increase the outflow rate from the nucleus by factors \u223c10, consistent with observational evidence for galaxy-scale AGN-driven outflows. (4) With AGN feedback, the predicted column density distribution to the BH is consistent with observations. Absent AGN feedback, the BH is isotropically obscured and there are not enough optically thin sightlines to explain type-I AGN. A 'torus-like' geometry arises self-consistently as AGN feedback evacuates gas in polar regions.",
"doi": "10.1093/mnras/stw289",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2016-05-01",
"series_number": "1",
"volume": "458",
"issue": "1",
"pages": "816-831"
},
{
"id": "authors:3a7bb-ah564",
"collection": "authors",
"collection_id": "3a7bb-ah564",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160301-111609246",
"type": "article",
"title": "The Necessity of Feedback Physics in Setting the Peak of the Initial Mass Function",
"author": [
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D"
},
{
"family_name": "Krumholz",
"given_name": "Mark R.",
"orcid": "0000-0003-3893-854X",
"clpid": "Krumholz-M-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "A popular theory of star formation is gravito-turbulent fragmentation, in which self-gravitating structures are created by turbulence-driven density fluctuations. Simple theories of isothermal fragmentation successfully reproduce the core mass function (CMF) which has a very similar shape to the initial mass function (IMF) of stars. However, numerical simulations of isothermal turbulent fragmentation thus far have not succeeded in identifying a fragment mass scale that is independent of the simulation resolution. Moreover, the fluid equations for magnetized, self-gravitating, isothermal turbulence are scale-free, and do not predict any characteristic mass. In this paper we show that, although an isothermal self-gravitating flow does produce a CMF with a mass scale imposed by the initial conditions, this scale changes as the parent cloud evolves. In addition, the cores that form undergo further fragmentation and after sufficient time forget about their initial conditions, yielding a scale-free pure power-law distribution dN/dM \u221d M^(\u22122) for the stellar IMF. We show that this problem can be alleviated by introducing additional physics that provides a termination scale for the cascade. Our candidate for such physics is a simple model for stellar radiation feedback. Radiative heating, powered by accretion on to forming stars, arrests the fragmentation cascade and imposes a characteristic mass scale that is nearly independent of the time-evolution or initial conditions in the star-forming cloud, and that agrees well with the peak of the observed IMF. In contrast, models that introduce a stiff equation of state for denser clouds but that do not explicitly include the effects of feedback do not yield an invariant IMF.",
"doi": "10.1093/mnras/stw315",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2016-05-01",
"series_number": "1",
"volume": "458",
"issue": "1",
"pages": "673-680"
},
{
"id": "authors:tvedj-azs60",
"collection": "authors",
"collection_id": "tvedj-azs60",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160510-102001148",
"type": "article",
"title": "Breathing FIRE: How Stellar Feedback Drives Radial Migration, Rapid Size Fluctuations, and Population Gradients in Low-Mass Galaxies",
"author": [
{
"family_name": "El-Badry",
"given_name": "Kareem",
"orcid": "0000-0002-6871-1752",
"clpid": "El-Badry-Kareem"
},
{
"family_name": "Wetzel",
"given_name": "Andrew",
"orcid": "0000-0003-0603-8942",
"clpid": "Wetzel-Andrew-R"
},
{
"family_name": "Geha",
"given_name": "Marla",
"orcid": "0000-0002-7007-9725",
"clpid": "Geha-Marla-C"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-Du\u0161an"
},
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-Claude-Andr\u00e9"
}
],
"abstract": "We examine the effects of stellar feedback and bursty star formation on low-mass galaxies (M_(star) = 2 \u00d7 10^6 \u2212 5 \u00d7 10^(10) M_\u2299) using the Feedback in Realistic Environments (FIRE) simulations. While previous studies emphasized the impact of feedback on dark matter profiles, we investigate the impact on the stellar component: kinematics, radial migration, size evolution, and population gradients. Feedback-driven outflows/inflows drive significant radial stellar migration over both short and long timescales via two processes: (1) outflowing/infalling gas can remain star-forming, producing young stars that migrate ~1 kpc within their first 100 Myr, and (2) gas outflows/inflows drive strong fluctuations in the global potential, transferring energy to all stars. These processes produce several dramatic effects. First, galaxies' effective radii can fluctuate by factors of >2 over ~200 Myr, and these rapid size fluctuations can account for much of the observed scatter in the radius at fixed M_(star). Second, the cumulative effects of many outflow/infall episodes steadily heat stellar orbits, causing old stars to migrate outward most strongly. This age-dependent radial migration mixes\u2014and even inverts\u2014intrinsic age and metallicity gradients. Thus, the galactic-archaeology approach of calculating radial star formation histories from stellar populations at z = 0 can be severely biased. These effects are strongest at M_(star) \u2248 10^(7\u20139.6) M_\u2299, the same regime where feedback most efficiently cores galaxies. Thus, detailed measurements of stellar kinematics in low-mass galaxies can strongly constrain feedback models and test baryonic solutions to small-scale problems in \u039bCDM.",
"doi": "10.3847/0004-637X/820/2/131",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2016-04-01",
"series_number": "2",
"volume": "820",
"issue": "2",
"pages": "Art. No. 131"
},
{
"id": "authors:kp1kc-j1309",
"collection": "authors",
"collection_id": "kp1kc-j1309",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160419-080939262",
"type": "article",
"title": "Evolution of Intrinsic Scatter in the SFR-Stellar Mass Correlation at 0.5 < z < 3",
"author": [
{
"family_name": "Kurczynski",
"given_name": "Peter",
"clpid": "Kurczynski-P"
},
{
"family_name": "Gawiser",
"given_name": "Eric",
"clpid": "Gawiser-E"
},
{
"family_name": "Acquaviva",
"given_name": "Viviana",
"orcid": "0000-0002-6788-6315",
"clpid": "Acquaviva-Viviana"
},
{
"family_name": "Bell",
"given_name": "Eric F.",
"clpid": "Bell-E-F"
},
{
"family_name": "Dekel",
"given_name": "Avishai",
"orcid": "0000-0003-4174-0374",
"clpid": "Dekel-A"
},
{
"family_name": "de Mello",
"given_name": "Duilia F.",
"clpid": "de-Mello-D-F"
},
{
"family_name": "Ferguson",
"given_name": "Henry C.",
"orcid": "0000-0001-7113-2738",
"clpid": "Ferguson-H-C"
},
{
"family_name": "Gardner",
"given_name": "Jonathan P.",
"clpid": "Gardner-J-P"
},
{
"family_name": "Grogin",
"given_name": "Norman A.",
"clpid": "Grogin-N-A"
},
{
"family_name": "Guo",
"given_name": "Yicheng",
"orcid": "0000-0003-2775-2002",
"clpid": "Guo-Yicheng"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Koekemoer",
"given_name": "Anton M.",
"orcid": "0000-0002-6610-2048",
"clpid": "Koekemoer-A-M"
},
{
"family_name": "Koo",
"given_name": "David C.",
"orcid": "0000-0003-3385-6799",
"clpid": "Koo-David-C"
},
{
"family_name": "Lee",
"given_name": "Seong-Kook",
"clpid": "Lee-Seong-Kook"
},
{
"family_name": "Mobasher",
"given_name": "Bahram",
"clpid": "Mobasher-B"
},
{
"family_name": "Primack",
"given_name": "Joel R.",
"orcid": "0000-0001-5091-5098",
"clpid": "Primack-J-R"
},
{
"family_name": "Rafelski",
"given_name": "Marc",
"orcid": "0000-0002-9946-4731",
"clpid": "Rafelski-M"
},
{
"family_name": "Soto",
"given_name": "Emmaris",
"clpid": "Soto-E"
},
{
"family_name": "Teplitz",
"given_name": "Harry I.",
"orcid": "0000-0002-7064-5424",
"clpid": "Teplitz-H-I"
}
],
"abstract": "We present estimates of intrinsic scatter in the star formation rate (SFR)\u2013stellar mass (M_*) correlation in the redshift range 0.5 < z < 3.0 and in the mass range 10^7 < M_*<10^(11)M_\u2299. We utilize photometry in the Hubble Ultradeep Field (HUDF12) and Ultraviolet Ultra Deep Field (UVUDF) campaigns and CANDELS/GOODS-S and estimate SFR, M_* from broadband spectral energy distributions and the best-available redshifts. The maximum depth of the UDF photometry (F160W 29.9 AB, 5\u03c3 depth) probes the SFR\u2013M_* correlation down to M_* ~ 10^7M_\u2299, a factor of 10\u2013100\u00d7 lower in M_* than previous studies, and comparable to dwarf galaxies in the local universe. We find the slope of the SFR\u2013M_* relationship to be near unity at all redshifts and the normalization to decrease with cosmic time. We find a moderate increase in intrinsic scatter with cosmic time from 0.2 to 0.4 dex across the epoch of peak cosmic star formation. None of our redshift bins show a statistically significant increase in intrinsic scatter at low mass. However, it remains possible that intrinsic scatter increases at low mass on timescales shorter than ~100 Myr. Our results are consistent with a picture of gradual and self-similar assembly of galaxies across more than three orders of magnitude in stellar mass from as low as 10^7M_\u2299.",
"doi": "10.3847/2041-8205/820/1/L1",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2016-03-20",
"series_number": "1",
"volume": "820",
"issue": "1",
"pages": "Art. No. L1"
},
{
"id": "authors:shvf8-51210",
"collection": "authors",
"collection_id": "shvf8-51210",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151022-134506351",
"type": "article",
"title": "The Fundamentally Different Dynamics of Dust and Gas in Molecular Clouds",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Lee",
"given_name": "Hyunseok",
"clpid": "Lee-Hyunseok"
}
],
"abstract": "We study the behaviour of large dust grains in turbulent molecular clouds (MCs). In primarily neutral regions, dust grains move as aerodynamic particles, not necessarily with the gas. We therefore directly simulate, for the first time, the behaviour of aerodynamic grains in highly supersonic, magnetohydrodynamic turbulence typical of MCs. We show that, under these conditions, grains with sizes a \u2273 0.01\u2009micron exhibit dramatic (exceeding factor \u223c1000) fluctuations in the local dust-to-gas ratio (implying large small-scale variations in abundances, dust cooling rates, and dynamics). The dust can form highly filamentary structures (which would be observed in both dust emission and extinction), which can be much thinner than the characteristic width of gas filaments. Sometimes, the dust and gas filaments are not even in the same location. The 'clumping factor' \u27e8n^2_(dust)\u27e9/\u27e8n_(dust)\u27e9^2 of the dust (critical for dust growth/coagulation/shattering) can reach \u223c100, for grains in the ideal size range. The dust clustering is maximized around scales \u223c 0.2\u2009pc\u2009(a/\u03bcm)\u2009(n_(gas)/100\u2009cm^(\u22123))^(\u22121), and is 'averaged out' on larger scales. However, because the density varies widely in supersonic turbulence, the dynamic range of scales (and interesting grain sizes) for these fluctuations is much broader than in the subsonic case. Our results are applicable to MCs of essentially all sizes and densities, but we note how Lorentz forces and other physics (neglected here) may change them in some regimes. We discuss the potentially dramatic consequences for star formation, dust growth and destruction, and dust-based observations of MCs.",
"doi": "10.1093/mnras/stv2745",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2016-03-11",
"series_number": "4",
"volume": "456",
"issue": "4",
"pages": "4174-4190"
},
{
"id": "authors:qftyj-8zg05",
"collection": "authors",
"collection_id": "qftyj-8zg05",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141222-150904506",
"type": "article",
"title": "Jumping the Gap: The Formation Conditions and Mass Function of 'Pebble-Pile' Planetesimals",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "In a turbulent proto-planetary disk, dust grains undergo large density fluctuations and under the right circumstances, these grain overdensities can overcome shear, turbulent, and gas pressure support to collapse under self-gravity (forming a \"pebble pile\" planetesimal). Using a simple analytic model for the fluctuations predicted in simulations, we estimate the rate-of-formation and mass function of self-gravitating, rapidly-collapsing planetesimal-mass bodies formed by this mechanism. The statistics of this process depend sensitively on the size/stopping time of the grains, disk surface density, and turbulent Mach numbers. However, when it occurs, we predict that the resulting planetesimal mass function is broad and quasi-universal, with a slope dN/dM \u221d M^(-(1-2)), spanning a size/mass range ~ 10-10^4 km (10^(-9)-5M_\u2295). Collapse to planetesimal through super-Earth masses is possible. The key condition is that grain density fluctuations reach large amplitudes on large scales, where gravitational instability proceeds most easily (collapse of small grains is strongly suppressed by turbulent vorticity). We show this leads to a new criterion for \"pebble-pile\" formation: \u01acs \u22730.05 ln (Q^(1/2)/Z_d)/ln(1+10\u0251^(1/4))~0.3\u03c8(Q,Z,\u0251) where \u01ac_s=t_s \u03a9 is the dimensionless particle stopping time. In a MMSN, this requires grains larger than \u0251 = (50, 1, 0.1)cm at r = (1, 30, 100)au. So at large radii (beyond the ice line), this may easily occur and seed core accretion. At small radii, it would depend on the existence of large \"boulders.\" However, because density fluctuations depend super-exponentially on T_s (inversely proportional to disk surface density), lower-density disks are more unstable. In fact, we predict that cm-sized grains at ~ 1 au will form pebble piles in a disk with ~ 10% the MMSN density, so planet formation at ~ au may generically occur \"late\" as disks are evaporating. We also predict that conditions become progressively more favorable for pebble-pile formation around lower-mass, cooler stars.",
"doi": "10.1093/mnras/stv2820",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2016-03-01",
"series_number": "3",
"volume": "456",
"issue": "3",
"pages": "2383-2405"
},
{
"id": "authors:xwvx7-vwn03",
"collection": "authors",
"collection_id": "xwvx7-vwn03",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150423-081343792",
"type": "article",
"title": "The Origin and Evolution of the Galaxy Mass-Metallicity Relation",
"author": [
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Zolman",
"given_name": "Nick",
"clpid": "Zolman-N"
},
{
"family_name": "Muratov",
"given_name": "Aexander L.",
"clpid": "Muratov-A-L"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
}
],
"abstract": "We use high-resolution cosmological zoom-in simulations from the Feedback in Realistic Environment (FIRE) project to study the galaxy mass\u2013metallicity relations (MZR) from z=0\u20136. These simulations include explicit models of the multi-phase ISM, star formation, and stellar feedback. The simulations cover halo masses M_(halo) = 10^9\u201310^(13) M_\u2609 and stellar masses M_* = 10^4\u201310^(11) M_\u2609 at z = 0 and have been shown to produce many observed galaxy properties\nfrom z = 0\u20136. For the first time, our simulations agree reasonably well with the observed mass\u2013metallicity relations at z = 0\u20133 for a broad range of galaxy masses. We predict the evolution of the MZR from z = 0\u20136, as log(Z_(gas)/Z_\u2609) = 12+log(O/H)-9.0 = 0.35 [log(M_*/M_\u2609) - 10] + 0.93exp(-0.43z) - 1.05 and log(Z_*/Z_\u2609) = [Fe=H] + 0.2 = 0.40 [log(M_*/M_\u2609)-10]+0.67exp(-0.50z)-1.04, for gas-phase and stellar metallicity, respectively.\nOur simulations suggest that the evolution of MZR is associated with the evolution of stellar/gas mass fractions at different redshifts, indicating the existence of a universal metallicity relation between stellar mass, gas mass, and metallicities. In our simulations, galaxies\nabove M_* = 10^6 M_\u2609 are able to retain a large fraction of their metals inside the halo, because metal-rich winds fail to escape completely and are recycled into the galaxy. This resolves a long-standing discrepancy between \"sub-grid\" wind models (and semi-analytic models) and\nobservations, where common sub-grid models cannot simultaneously reproduce the MZR and the stellar mass functions.",
"doi": "10.1093/mnras/stv2659",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2016-02-21",
"series_number": "2",
"volume": "456",
"issue": "2",
"pages": "2140-2156"
},
{
"id": "authors:97g9h-p3q28",
"collection": "authors",
"collection_id": "97g9h-p3q28",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150615-061712828",
"type": "article",
"title": "Accurate, meshless methods for magnetohydrodynamics",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Raives",
"given_name": "Matthias J.",
"clpid": "Raives-M-J"
}
],
"abstract": "Recently, we explored new meshless finite-volume Lagrangian methods for hydrodynamics: the 'meshless finite mass' (MFM) and 'meshless finite volume' (MFV) methods; these capture advantages of both smoothed particle hydrodynamics (SPH) and adaptive mesh refinement (AMR) schemes. We extend these to include ideal magnetohydrodynamics (MHD). The MHD equations are second-order consistent and conservative. We augment these with a divergence-cleaning scheme, which maintains \u2207\u22c5B\u22480\u2207\u22c5B\u22480. We implement these in the code GIZMO, together with state-of-the-art SPH MHD. We consider a large test suite, and show that on all problems the new methods are competitive with AMR using constrained transport (CT) to ensure \u2207\u22c5B=0\u2207\u22c5B=0. They correctly capture the growth/structure of the magnetorotational instability, MHD turbulence, and launching of magnetic jets, in some cases converging more rapidly than state-of-the-art AMR. Compared to SPH, the MFM/MFV methods exhibit convergence at fixed neighbour number, sharp shock-capturing, and dramatically reduced noise, divergence errors, and diffusion. Still, 'modern' SPH can handle most test problems, at the cost of larger kernels and 'by hand' adjustment of artificial diffusion. Compared to non-moving meshes, the new methods exhibit enhanced 'grid noise' but reduced advection errors and diffusion, easily include self-gravity, and feature velocity-independent errors and superior angular momentum conservation. They converge more slowly on some problems (smooth, slow-moving flows), but more rapidly on others (involving advection/rotation). In all cases, we show divergence control beyond the Powell 8-wave approach is necessary, or all methods can converge to unphysical answers even at high resolution.",
"doi": "10.1093/mnras/stv2180",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2016-01-01",
"series_number": "1",
"volume": "455",
"issue": "1",
"pages": "51-88"
},
{
"id": "authors:3738e-67c06",
"collection": "authors",
"collection_id": "3738e-67c06",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160204-155313897",
"type": "article",
"title": "A simple phenomenological model for grain clustering in turbulence",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We propose a simple model for density fluctuations of aerodynamic grains, embedded in a turbulent, gravitating gas disc. The model combines a calculation for the behaviour of a group of grains encountering a single turbulent eddy, with a hierarchical approximation of the eddy statistics. This makes analytic predictions for a range of quantities including: distributions of grain densities, power spectra and correlation functions of fluctuations, and maximum grain densities reached. We predict how these scale as a function of grain drag time t_s, spatial scale, grain-to-gas mass ratio \u03c1\u0303 \u03c1~, strength of turbulence \u03b1, and detailed disc properties. We test these against numerical simulations with various turbulence-driving mechanisms. The simulations agree well with the predictions, spanning t_s\u2009\u03a9 \u223c 10^(\u22124)\u201310, \u03c1\u0303 \u223c0\u22123\u03c1~\u223c0\u22123, \u03b1 \u223c 10^(\u221210)\u201310^(\u22122). Results from 'turbulent concentration' simulations and laboratory experiments are also predicted as a special case. Vortices on a wide range of scales disperse and concentrate grains hierarchically. For small grains this is most efficient in eddies with turnover time comparable to the stopping time, but fluctuations are also damped by local gas-grain drift. For large grains, shear and gravity lead to a much broader range of eddy scales driving fluctuations, with most power on the largest scales. The grain density distribution has a log-Poisson shape, with fluctuations for large grains up to factors \u22731000. We provide simple analytic expressions for the predictions, and discuss implications for planetesimal formation, grain growth, and the structure of turbulence.",
"doi": "10.1093/mnras/stv2226",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2016-01-01",
"series_number": "1",
"volume": "455",
"issue": "1",
"pages": "89-111"
},
{
"id": "authors:6mb8n-frm10",
"collection": "authors",
"collection_id": "6mb8n-frm10",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160205-120908533",
"type": "article",
"title": "The impact of baryonic physics on the structure of dark matter haloes: the view from the FIRE cosmological simulations",
"author": [
{
"family_name": "Chan",
"given_name": "T. K.",
"orcid": "0000-0003-2544-054X",
"clpid": "Chan-Tsang-Keung"
},
{
"family_name": "Kere\u0161",
"given_name": "D.",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "O\u00f1orbe",
"given_name": "J.",
"clpid": "O\u00f1orbe-J"
},
{
"family_name": "Hopkins",
"given_name": "P. F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Muratov",
"given_name": "A. L.",
"clpid": "Muratov-A-L"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "C.-A.",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Quataert",
"given_name": "E.",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
}
],
"abstract": "We study the distribution of cold dark matter (CDM) in cosmological simulations from the FIRE (Feedback In Realistic Environments) project, for M_* \u223c 10^(4\u201311)\u2009M_\u2299 galaxies in M_h \u223c 10^(9\u201312)\u2009M_\u2299 haloes. FIRE incorporates explicit stellar feedback in the multiphase interstellar medium, with energetics from stellar population models. We find that stellar feedback, without 'fine-tuned' parameters, greatly alleviates small-scale problems in CDM. Feedback causes bursts of star formation and outflows, altering the DM distribution. As a result, the inner slope of the DM halo profile (\u03b1) shows a strong mass dependence: profiles are shallow at M_h \u223c 10^(10)\u201310^(11)\u2009M_\u2299 and steepen at higher/lower masses. The resulting core sizes and slopes are consistent with observations. This is broadly consistent with previous work using simpler feedback schemes, but we find steeper mass dependence of \u03b1, and relatively late growth of cores. Because the star formation efficiency M_*/M_h is strongly halo mass dependent, a rapid change in \u03b1 occurs around M_h \u223c 10^(10)\u2009M_\u2299 (M_* \u223c 10^6\u201310^7\u2009M_\u2299), as sufficient feedback energy becomes available to perturb the DM. Large cores are not established during the period of rapid growth of haloes because of ongoing DM mass accumulation. Instead, cores require several bursts of star formation after the rapid build-up has completed. Stellar feedback dramatically reduces circular velocities in the inner kpc of massive dwarfs; this could be sufficient to explain the 'Too Big To Fail' problem without invoking non-standard DM. Finally, feedback and baryonic contraction in Milky Way-mass haloes produce DM profiles slightly shallower than the Navarro\u2013Frenk\u2013White profile, consistent with the normalization of the observed Tully\u2013Fisher relation.",
"doi": "10.1093/mnras/stv2165",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2015-12-11",
"series_number": "3",
"volume": "454",
"issue": "3",
"pages": "2981-3001"
},
{
"id": "authors:c9df1-jym11",
"collection": "authors",
"collection_id": "c9df1-jym11",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160205-132422140",
"type": "article",
"title": "Gusty, gaseous flows of FIRE: galactic winds in cosmological simulations with explicit stellar feedback",
"author": [
{
"family_name": "Muratov",
"given_name": "Alexander L.",
"clpid": "Muratov-A-L"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N"
}
],
"abstract": "We present an analysis of the galaxy-scale gaseous outflows from the Feedback in Realistic Environments (FIRE) simulations. This suite of hydrodynamic cosmological zoom simulations resolves formation of star-forming giant molecular clouds to z = 0, and features an explicit stellar feedback model on small scales. Our simulations reveal that high-redshift galaxies undergo bursts of star formation followed by powerful gusts of galactic outflows that eject much of the interstellar medium and temporarily suppress star formation. At low redshift, however, sufficiently massive galaxies corresponding to L* progenitors develop stable discs and switch into a continuous and quiescent mode of star formation that does not drive outflows far into the halo. Mass-loading factors for winds in L* progenitors are \u03b7 \u2248 10 at high redshift, but decrease to \u03b7 \u226a 1 at low redshift. Although lower values of \u03b7 are expected as haloes grow in mass over time, we show that the strong suppression of outflows with decreasing redshift cannot be explained by mass evolution alone. Circumgalactic outflow velocities are variable and broadly distributed, but typically range between one and three times the circular velocity of the halo. Much of the ejected material builds a reservoir of enriched gas within the circumgalactic medium, some of which could be later recycled to fuel further star formation. However, a fraction of the gas that leaves the virial radius through galactic winds is never regained, causing most haloes with mass M_h \u2264 10^(12)\u2009M_\u2299 to be deficient in baryons compared to the cosmic mean by z = 0.",
"doi": "10.1093/mnras/stv2126",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2015-12-11",
"series_number": "3",
"volume": "454",
"issue": "3",
"pages": "2691-2713"
},
{
"id": "authors:dj1ct-t8197",
"collection": "authors",
"collection_id": "dj1ct-t8197",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160205-133222970",
"type": "article",
"title": "Forged in FIRE: cusps, cores and baryons in low-mass dwarf galaxies",
"author": [
{
"family_name": "O\u00f1orbe",
"given_name": "Jose",
"clpid": "O\u00f1orbe-J"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-J-S"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
}
],
"abstract": "We present multiple ultrahigh resolution cosmological hydrodynamic simulations of M_\u2605 \u2243 10^(4\u20136.3)\u2009M_\u2299 dwarf galaxies that form within two M_(vir) = 10^(9.5\u201310)\u2009M_\u2299 dark matter halo initial conditions. Our simulations rely on the Feedback in Realistic Environments (FIRE) implementation of star formation feedback and were run with high enough force and mass resolution to directly resolve structure on the \u223c200 pc scales. The resultant galaxies sit on the M_\u2605 versus M_(vir) relation required to match the Local Group stellar mass function via abundance matching. They have bursty star formation histories and also form with half-light radii and metallicities that broadly match those observed for local dwarfs at the same stellar mass. We demonstrate that it is possible to create a large (\u223c1 kpc) constant-density dark matter core in a cosmological simulation of an M_\u2605 \u2243 10^(6.3)\u2009M_\u2299 dwarf galaxy within a typical M_(vir) = 10^(10)\u2009M_\u2299 halo \u2013 precisely the scale of interest for resolving the 'too big to fail' problem. However, these large cores are not ubiquitous and appear to correlate closely with the star formation histories of the dwarfs: dark matter cores are largest in systems that form their stars late (z \u2272 2), after the early epoch of cusp building mergers has ended. Our M_\u2605 \u2243 10^4\u2009M_\u2299 dwarf retains a cuspy dark matter halo density profile that matches that of a dark-matter-only run of the same system. Though ancient, most of the stars in our ultrafaint form after reionization; the ultraviolet field acts mainly to suppress fresh gas accretion, not to boil away gas that is already present in the protodwarf.",
"doi": "10.1093/mnras/stv2072",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2015-12-01",
"series_number": "2",
"volume": "454",
"issue": "2",
"pages": "2092-2106"
},
{
"id": "authors:gw8bs-awy88",
"collection": "authors",
"collection_id": "gw8bs-awy88",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150423-090135687",
"type": "article",
"title": "Sweating the small stuff: simulating dwarf galaxies, ultra-faint dwarf galaxies, and their own tiny satellites",
"author": [
{
"family_name": "Wheeler",
"given_name": "Coral",
"clpid": "Wheeler-C"
},
{
"family_name": "O\u00f1orbe",
"given_name": "Jos\u00e9",
"clpid": "O\u00f1orbe-J"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-J-S"
},
{
"family_name": "Boylan-Kolchin",
"given_name": "Michael",
"orcid": "0000-0002-9604-343X",
"clpid": "Boylan-Kolchin-M"
},
{
"family_name": "Elbert",
"given_name": "Oliver",
"clpid": "Elbert-O-D"
},
{
"family_name": "Garrison-Kimmel",
"given_name": "Shea",
"orcid": "0000-0002-4655-8128",
"clpid": "Garrison-Kimmel-S"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "We present Feedback in Realistic Environment (FIRE)/GIZMO hydrodynamic zoom-in simulations of isolated dark matter haloes, two each at the mass of classical dwarf galaxies (M_(vir) \u2243 10^(10)\u2009\u2009M_\u2299) and ultra-faint galaxies (M_(vir) \u2243 10^9\u2009\u2009M_\u2299), and with two feedback implementations. The resulting central galaxies lie on an extrapolated abundance matching relation from M_\u2605 \u2243 10^6 to 10^4\u2009\u2009M_\u2299 without a break. Every host is filled with subhaloes, many of which form stars. Each of our dwarfs with M_\u2605 \u2243 10^6\u2009\u2009M_\u2299 has 1\u20132 well-resolved satellites with M_\u2605 = 3-200 \u00d7 10^3\u2009\u2009M_\u2299. Even our isolated ultra-faint galaxies have star-forming subhaloes. If this is representative, dwarf galaxies throughout the Universe should commonly host tiny satellite galaxies of their own. We combine our results with the Exploring the Local Volume in Simulations (ELVIS) simulations to show that targeting \u223c 50\u2009kpc regions around nearby isolated dwarfs could increase the chances of discovering ultra-faint galaxies by \u223c35\u2009per\u2009cent compared to random pointings, and specifically identify the region around the Phoenix dwarf galaxy as a good potential target. The well-resolved ultra-faint galaxies in our simulations (M_\u2605 \u2243 3-30 \u00d7 10^3\u2009\u2009M_\u2299) form within M_(peak) \u2243 0.5-3 \u00d7 10^9\u2009\u2009M_\u2299 haloes. Each has a uniformly ancient stellar population ( > 10\u2009Gyr) owing to reionization-related quenching. More massive systems, in contrast, all have late-time star formation. Our results suggest that M_(halo) \u2243 5 \u00d7 10^9\u2009\u2009M_\u2299 is a probable dividing line between haloes hosting reionization 'fossils' and those hosting dwarfs that can continue to form stars in isolation after reionization.",
"doi": "10.1093/mnras/stv1691",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2015-10-21",
"series_number": "2",
"volume": "453",
"issue": "2",
"pages": "1305-1316"
},
{
"id": "authors:kpyqn-vmr65",
"collection": "authors",
"collection_id": "kpyqn-vmr65",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150330-163106550",
"type": "article",
"title": "The Difficulty Getting High Escape Fractions of Ionizing Photons from High-redshift Galaxies: a View from the FIRE Cosmological Simulations",
"author": [
{
"family_name": "Ma",
"given_name": "Xiangcheng",
"orcid": "0000-0001-8091-2349",
"clpid": "Ma-Xiangcheng"
},
{
"family_name": "Kasen",
"given_name": "Daniel",
"clpid": "Kasen-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
}
],
"abstract": "We present a series of high-resolution (20\u20132000 M\u2299, 0.1\u20134 pc) cosmological zoom-in simulations at z \u2273 6 from the Feedback In Realistic Environment (FIRE) project. These simulations cover halo masses 10^9\u201310^(11)\u2009M\u2299 and rest-frame ultraviolet magnitude M_(UV) = \u22129 to \u221219. These simulations include explicit models of the multi-phase ISM, star formation, and stellar feedback, which produce reasonable galaxy properties at z = 0\u20136. We post-process the snapshots with a radiative transfer code to evaluate the escape fraction (f_(esc)) of hydrogen ionizing photons. We find that the instantaneous f_(esc) has large time variability (0.01\u201320\u2009per\u2009cent), while the time-averaged f_(esc) over long time-scales generally remains \u2272 5\u2009per\u2009cent, considerably lower than the estimate in many reionization models. We find no strong dependence of f_(esc) on galaxy mass or redshift. In our simulations, the intrinsic ionizing photon budgets are dominated by stellar populations younger than 3 Myr, which tend to be buried in dense birth clouds. The escaping photons mostly come from populations between 3 and 10 Myr, whose birth clouds have been largely cleared by stellar feedback. However, these populations only contribute a small fraction of intrinsic ionizing photon budgets according to standard stellar population models. We show that f_(esc) can be boosted to high values, if stellar populations older than 3 Myr produce more ionizing photons than standard stellar population models (as motivated by, e.g. models including binaries). By contrast, runaway stars with velocities suggested by observations can enhance f_(esc) by only a small fraction. We show that 'sub-grid' star formation models, which do not explicitly resolve star formation in dense clouds with n \u226b 1\u2009cm^(\u22123), will dramatically overpredict f_(esc).",
"doi": "10.1093/mnras/stv1679",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2015-10-11",
"series_number": "1",
"volume": "453",
"issue": "1",
"pages": "960-975"
},
{
"id": "authors:dx5ay-b8e26",
"collection": "authors",
"collection_id": "dx5ay-b8e26",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150729-091600504",
"type": "article",
"title": "The formation of submillimetre-bright galaxies from gas infall over a billion years",
"author": [
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-D"
},
{
"family_name": "Turk",
"given_name": "Matthew",
"clpid": "Turk-M"
},
{
"family_name": "Feldmann",
"given_name": "Robert",
"orcid": "0000-0002-1109-1919",
"clpid": "Feldmann-R"
},
{
"family_name": "Robitaille",
"given_name": "Thomas",
"orcid": "0000-0002-8642-1329",
"clpid": "Robitaille-T-P"
},
{
"family_name": "Hopkins",
"given_name": "Philip",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Thompson",
"given_name": "Robert",
"clpid": "Thompson-R"
},
{
"family_name": "Hayward",
"given_name": "Christopher",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Ball",
"given_name": "David",
"clpid": "Ball-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
}
],
"abstract": "Submillimetre-bright galaxies at high redshift are the most luminous, heavily star-forming galaxies in the Universe and are characterized by prodigious emission in the far-infrared, with a flux of at least five millijanskys at a wavelength of 850 micrometres. They reside in haloes with masses about 10^(13) times that of the Sun, have low gas fractions compared to main-sequence disks at a comparable redshift, trace complex environments and are not easily observable at optical wavelengths. Their physical origin remains unclear. Simulations have been able to form galaxies with the requisite luminosities, but have otherwise been unable to simultaneously match the stellar masses, star formation rates, gas fractions and environments. Here we report a cosmological hydrodynamic galaxy formation simulation that is able to form a submillimetre galaxy that simultaneously satisfies the broad range of observed physical constraints. We find that groups of galaxies residing in massive dark matter haloes have increasing rates of star formation that peak at collective rates of about 500\u20131,000 solar masses per year at redshifts of two to three, by which time the interstellar medium is sufficiently enriched with metals that the region may be observed as a submillimetre-selected system. The intense star formation rates are fuelled in part by the infall of a reservoir gas supply enabled by stellar feedback at earlier times, not through major mergers. With a lifetime of nearly a billion years, our simulations show that the submillimetre-bright phase of high-redshift galaxies is prolonged and associated with significant mass buildup in early-Universe proto-clusters, and that many submillimetre-bright galaxies are composed of numerous unresolved components (for which there is some observational evidence).",
"doi": "10.1038/nature15383",
"issn": "0028-0836",
"publisher": "Nature Publishing Group",
"publication": "Nature",
"publication_date": "2015-09-24",
"series_number": "7570",
"volume": "525",
"issue": "7570",
"pages": "496-499"
},
{
"id": "authors:24am3-n5n50",
"collection": "authors",
"collection_id": "24am3-n5n50",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150423-093313691",
"type": "article",
"title": "The creation and persistence of a misaligned gas disc in a simulated early-type galaxy",
"author": [
{
"family_name": "van de Voort",
"given_name": "Freeke",
"orcid": "0000-0002-6301-638X",
"clpid": "van-de-Voort-F"
},
{
"family_name": "Davis",
"given_name": "Timothy A.",
"clpid": "Davis-T-A"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Massive early-type galaxies (ETGs) commonly have gas discs which are kinematically misaligned with the stellar component. These discs feel a torque from the stars and the angular momentum vectors are expected to align quickly. We present results on the evolution of a misaligned gas disc in a cosmological simulation of a massive ETG from the feedback in realistic environments project. This galaxy experiences a merger which, together with a strong galactic wind, removes most of the original gas disc. The galaxy subsequently reforms a gas disc through accretion of cold gas, but it is initially 120\u00b0 misaligned with the stellar rotation axis. This misalignment persists for about 2 Gyr before the gas\u2013star misalignment angle drops below 20\u00b0. The time it takes for the gaseous and stellar components to align is much longer than previously thought, because the gas disc is accreting a significant amount of mass for about 1.5 Gyr after the merger, during which the angular momentum change induced by accreted gas dominates over that induced by stellar torques. Once the gas accretion rate has decreased sufficiently, the gas disc decouples from the surrounding halo gas and realigns with the stellar component in about six dynamical times. During the late evolution of the misaligned gas disc, the centre aligns faster than the outskirts, resulting in a warped disc. We discuss the observational consequences of the long survival of our misaligned gas disc and how our results can be used to calibrate merger rate estimates from observed gas misalignments.",
"doi": "10.1093/mnras/stv1217",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2015-08-11",
"series_number": "3",
"volume": "451",
"issue": "3",
"pages": "3269-3277"
},
{
"id": "authors:3vx3r-y5584",
"collection": "authors",
"collection_id": "3vx3r-y5584",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151002-124114892",
"type": "article",
"title": "Mapping the core mass function to the initial mass function",
"author": [
{
"family_name": "Guszejnov",
"given_name": "D\u00e1vid",
"orcid": "0000-0001-5541-3150",
"clpid": "Guszejnov-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "It has been shown that fragmentation within self-gravitating, turbulent molecular clouds ('turbulent fragmentation') can naturally explain the observed properties of protostellar cores, including the core mass function (CMF). Here, we extend recently developed analytic models for turbulent fragmentation to follow the time-dependent hierarchical fragmentation of self-gravitating cores, until they reach effectively infinite density (and form stars). We show that turbulent fragmentation robustly predicts two key features of the initial mass function (IMF). First, a high-mass power-law scaling very close to the Salpeter slope, which is a generic consequence of the scale-free nature of turbulence and self-gravity. We predict the IMF slope (\u22122.3) is slightly steeper than the CMF slope (\u22122.1), owing to the slower collapse and easier fragmentation of large cores. Secondly, a turnover mass, which is set by a combination of the CMF turnover mass (a couple solar masses, determined by the 'sonic scale' of galactic turbulence, and so weakly dependent on galaxy properties), and the equation of state (EOS). A 'soft' EOS with polytropic index \u03b3 < 1.0 predicts that the IMF slope becomes 'shallow' below the sonic scale, but fails to produce the full turnover observed. An EOS, which becomes 'stiff' at sufficiently low surface densities \u03a3gas \u223c 5000\u2009M_\u2299\u2009pc^(\u22122), and/or models, where each collapsing core is able to heat and effectively stiffen the EOS of a modest mass (\u223c0.02\u2009M_\u2299) of surrounding gas, are able to reproduce the observed turnover. Such features are likely a consequence of more detailed chemistry and radiative feedback.",
"doi": "10.1093/mnras/stv872",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2015-07-11",
"series_number": "4",
"volume": "450",
"issue": "4",
"pages": "4137-4149"
},
{
"id": "authors:w7nzd-mzb73",
"collection": "authors",
"collection_id": "w7nzd-mzb73",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141202-094306473",
"type": "article",
"title": "A new class of accurate, mesh-free hydrodynamic simulation methods",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We present two new Lagrangian methods for hydrodynamics, in a systematic comparison with moving-mesh, smoothed particle hydrodynamics (SPH), and stationary (non-moving) grid methods. The new methods are designed to simultaneously capture advantages of both SPH and grid-based/adaptive mesh refinement (AMR) schemes. They are based on a kernel discretization of the volume coupled to a high-order matrix gradient estimator and a Riemann solver acting over the volume 'overlap'. We implement and test a parallel, second-order version of the method with self-gravity and cosmological integration, in the code gizmo:1 this maintains exact mass, energy and momentum conservation; exhibits superior angular momentum conservation compared to all other methods we study; does not require 'artificial diffusion' terms; and allows the fluid elements to move with the flow, so resolution is automatically adaptive. We consider a large suite of test problems, and find that on all problems the new methods appear competitive with moving-mesh schemes, with some advantages (particularly in angular momentum conservation), at the cost of enhanced noise. The new methods have many advantages versus SPH: proper convergence, good capturing of fluid-mixing instabilities, dramatically reduced 'particle noise' and numerical viscosity, more accurate sub-sonic flow evolution, and sharp shock-capturing. Advantages versus non-moving meshes include: automatic adaptivity, dramatically reduced advection errors and numerical overmixing, velocity-independent errors, accurate coupling to gravity, good angular momentum conservation and elimination of 'grid alignment' effects. We can, for example, follow hundreds of orbits of gaseous discs, while AMR and SPH methods break down in a few orbits. However, fixed meshes minimize 'grid noise'. These differences are important for a range of astrophysical problems.",
"doi": "10.1093/mnras/stv195",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2015-06-11",
"series_number": "1",
"volume": "450",
"issue": "1",
"pages": "53-110"
},
{
"id": "authors:ntv4z-nxk43",
"collection": "authors",
"collection_id": "ntv4z-nxk43",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141217-095337831",
"type": "article",
"title": "Neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history",
"author": [
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Muratov",
"given_name": "Aexander L.",
"clpid": "Muratov-A-L"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N"
}
],
"abstract": "We use high-resolution cosmological zoom-in simulations from the FIRE (Feedback in Realistic Environments) project to make predictions for the covering fractions of neutral hydrogen around galaxies at z = 2\u20134. These simulations resolve the interstellar medium of galaxies and explicitly implement a comprehensive set of stellar feedback mechanisms. Our simulation sample consists of 16 main haloes covering the mass range M_h \u2248 10^9\u20136 \u00d7 10^(12) M_\u2299 at z = 2, including 12 haloes in the mass range M_h \u223c 10^(11)\u201310^(12) M_\u2299 corresponding to Lyman break galaxies (LBGs). We process our simulations with a ray tracing method to compute the ionization state of the gas. Galactic winds increase the H\u2009i covering fractions in galaxy haloes by direct ejection of cool gas from galaxies and through interactions with gas inflowing from the intergalactic medium. Our simulations predict H\u2009i covering fractions for Lyman limit systems (LLSs) consistent with measurements around z \u223c 2\u20132.5 LBGs; these covering fractions are a factor \u223c2 higher than our previous calculations without galactic winds. The fractions of H\u2009i absorbers arising in inflows and in outflows are on average \u223c50\u2009per\u2009cent but exhibit significant time variability, ranging from \u223c10 to \u223c90\u2009per\u2009cent. For our most massive haloes, we find a factor \u223c3 deficit in the LLS covering fraction relative to what is measured around quasars at z \u223c 2, suggesting that the presence of a quasar may affect the properties of halo gas on \u223c100 kpc scales. The predicted covering fractions, which decrease with time, peak at M_h \u223c 10^(11)\u201310^(12) M_\u2299, near the peak of the star formation efficiency in dark matter haloes. In our simulations, star formation and galactic outflows are highly time dependent; H\u2009i covering fractions are also time variable but less so because they represent averages over large areas.",
"doi": "10.1093/mnras/stv336",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2015-05-01",
"series_number": "1",
"volume": "449",
"issue": "1",
"pages": "987-1003"
},
{
"id": "authors:dqfj6-76x35",
"collection": "authors",
"collection_id": "dqfj6-76x35",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141217-135454543",
"type": "article",
"title": "Galactic r-process enrichment by neutron star mergers in cosmological simulations of a Milky Way-mass galaxy",
"author": [
{
"family_name": "van de Voort",
"given_name": "Freeke",
"orcid": "0000-0002-6301-638X",
"clpid": "van-de-Voort-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
}
],
"abstract": "We quantify the stellar abundances of neutron-rich r-process nuclei in cosmological zoom-in simulations of a Milky Way-mass galaxy from the Feedback In Realistic Environments project. The galaxy is enriched with r-process elements by binary neutron star (NS) mergers and with\niron and other metals by supernovae. These calculations include key hydrodynamic mixing processes not present in standard semi-analytic chemical evolution models, such as galactic winds and hydrodynamic flows associated with structure formation. We explore a range of models for the rate and delay time of NS mergers, intended to roughly bracket the wide range of models consistent with current observational constraints. We show that NS mergers can\nproduce [r-process/Fe] abundance ratios and scatter that appear reasonably consistent with observational constraints. At low metallicity, [Fe/H] \u227e \u22122, we predict there is a wide range of stellar r-process abundance ratios, with both supersolar and subsolar abundances. Low metallicity stars or stars that are outliers in their r-process abundance ratios are, on average, formed at high redshift and located at large galactocentric radius. Because NS mergers are rare, our results are not fully converged with respect to resolution, particularly at low metallicity. However, the uncertain rate and delay time distribution of NS mergers introduce an uncertainty in the r-process abundances comparable to that due to finite numerical resolution. Overall, our results are consistent with NS mergers being the source of most of the r-process nuclei in the Universe.",
"doi": "10.1093/mnras/stu2404",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2015-02-11",
"series_number": "1",
"volume": "447",
"issue": "1",
"pages": "140-148"
},
{
"id": "authors:zktbr-6fq50",
"collection": "authors",
"collection_id": "zktbr-6fq50",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140707-083959908",
"type": "article",
"title": "Some Stars are Totally Metal: A New Mechanism Driving Dust Across Star-Forming Clouds, and Consequences for Planets, Stars, and Galaxies",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Dust grains in neutral gas behave as aerodynamic particles, so they can develop large local density fluctuations entirely independent of gas density fluctuations. Specifically, gas turbulence can drive order-of-magnitude \"resonant\" fluctuations in the dust density on scales\nwhere the gas stopping/drag timescale is comparable to the turbulent eddy turnover time. Here we show that for large grains (size \u2273 0.1 \u00b5m, containing most grain mass) in sufficiently large molecular clouds (radii \u2273 1 - 10pc, masses \u2273 10^4M_\u2299), this scale becomes longer than the\ncharacteristic sizes of pre-stellar cores (the sonic length), so large fluctuations in the dust-to-gas ratio are imprinted on cores. As a result, star clusters and protostellar disks formed in large clouds should exhibit substantial abundance spreads in the elements preferentially\nfound in large grains (C, O). This naturally predicts populations of carbon-enhanced stars,\ncertain highly unusual stellar populations observed in nearby open clusters, and may explain\nthe \"UV upturn\" in early-type galaxies. It will also dramatically change planet formation in\nthe resulting protostellar disks, by preferentially \"seeding\" disks with an enhancement in large\ncarbonaceous or silicate grains. The relevant threshold for this behavior scales simply with\ncloud densities and temperatures, making straightforward predictions for clusters in starbursts\nand high-redshift galaxies. Because of the selective sorting by size, this process is not visible\nin extinction mapping. We also predict the shape of the abundance distribution \u2013 when these\nfluctuations occur, a small fraction of the cores are actually seeded with abundances Z ~ 100\u3008Z\u3009 such that they are almost \"totally metal\" (Z ~ 1)! Assuming the cores collapse, these\ntotally metal stars would be rare (1 in ~ 10^4 in clusters where this occurs), but represent a\nfundamentally new stellar evolution channel.",
"doi": "10.1088/0004-637X/797/1/59",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2014-12-10",
"series_number": "1",
"volume": "797",
"issue": "1",
"pages": "Art. No. 59"
},
{
"id": "authors:cr6tz-6z359",
"collection": "authors",
"collection_id": "cr6tz-6z359",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141210-153003024",
"type": "article",
"title": "Stars fight back",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Galaxies contain fewer stars than predicted. The discovery of a massive galactic\noutflow of molecular gas in a compact galaxy, which forms stars 100 times faster\nthan the Milky Way, may help to explain why.",
"doi": "10.1038/516044a",
"issn": "0028-0836",
"publisher": "Nature Publishing Group",
"publication": "Nature",
"publication_date": "2014-12-04",
"series_number": "7529",
"volume": "516",
"issue": "7529",
"pages": "44-45"
},
{
"id": "authors:9a5hj-kyd21",
"collection": "authors",
"collection_id": "9a5hj-kyd21",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141201-101549262",
"type": "article",
"title": "Do we expect most AGN to live in discs?",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kocevski",
"given_name": "Dale D.",
"clpid": "Kocevski-D-D"
},
{
"family_name": "Bundy",
"given_name": "Kevin",
"orcid": "0000-0001-9742-3138",
"clpid": "Bundy-K-A"
}
],
"abstract": "Recent observations have indicated that a large fraction of the low- to intermediate-luminosity AGN population lives in disc-dominated hosts, while the more luminous quasars live in bulge-dominated hosts (that may or may not be major merger remnants), in conflict with some previous model predictions. We therefore build and compare a semi-empirical model for AGN fuelling which accounts for both merger and non-merger 'triggering'. In particular, we show that the 'stochastic accretion' model \u2013 in which fuelling in disc galaxies is essentially a random process arising whenever dense gas clouds reach the nucleus \u2013 provides a good match to the present observations at low/intermediate luminosities. However, it falls short of the high-luminosity population. We combine this with models for major merger-induced AGN fueling, which lead to rarer but more luminous events, and predict the resulting abundance of disc-dominated and bulge-dominated AGN host galaxies as a function of luminosity and redshift. We compile and compare observational constraints from z \u223c 0 to 2. The models and observations generically show a transition from disc to bulge dominance in hosts near the Seyfert-quasar transition, at all redshifts. 'Stochastic' fuelling dominates AGN by number (dominant at low luminosity), and dominates black hole (BH) growth below the 'knee' in the present-day BH mass function ( \u2272 10^7 \u2009M_\u2299). However, it accounts for just \u223c10 per cent of BH mass growth at masses \u2273 10^8 \u2009M_\u2299. In total, fuelling in discy hosts accounts for \u223c30 per cent of the total AGN luminosity density/BH mass density. The combined model also accurately predicts the AGN luminosity function and clustering/bias as a function of luminosity and redshift; however, we argue that these are not sensitive probes of BH fuelling mechanisms.",
"doi": "10.1093/mnras/stu1736",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2014-11-21",
"series_number": "1",
"volume": "445",
"issue": "1",
"pages": "823-834"
},
{
"id": "authors:qmzmc-sjx82",
"collection": "authors",
"collection_id": "qmzmc-sjx82",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131125-073705692",
"type": "article",
"title": "Galaxies on FIRE (Feedback In Realistic Environments): Stellar Feedback Explains Cosmologically Inefficient Star Formation",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "O\u00f1orbe",
"given_name": "Jos\u00e9",
"clpid": "O\u00f1orbe-J"
},
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
},
{
"family_name": "Bullock",
"given_name": "James S.",
"orcid": "0000-0003-4298-5082",
"clpid": "Bullock-J-S"
}
],
"abstract": "We present a series of high-resolution cosmological simulations of galaxy formation to z = 0, spanning halo masses \u223c10^8\u201310^(13)\u2009M\u2299, and stellar masses \u223c10^4\u201310^(11)\u2009M\u2299. Our simulations include fully explicit treatment of the multiphase interstellar medium and stellar feedback. The stellar feedback inputs (energy, momentum, mass, and metal fluxes) are taken directly from stellar population models. These sources of feedback, with zero adjusted parameters, reproduce the observed relation between stellar and halo mass up to M_(halo) \u223c 10^(12)\u2009M\u2299. We predict weak redshift evolution in the M*\u2013M_(halo) relation, consistent with current constraints to z > 6. We find that the M*\u2013M_(halo) relation is insensitive to numerical details, but is sensitive to feedback physics. Simulations with only supernova feedback fail to reproduce observed stellar masses, particularly in dwarf and high-redshift galaxies: radiative feedback (photoheating and radiation pressure) is necessary to destroy giant molecular clouds and enable efficient coupling of later supernovae to the gas. Star formation rates (SFRs) agree well with the observed Kennicutt relation at all redshifts. The galaxy-averaged Kennicutt relation is very different from the numerically imposed law for converting gas into stars, and is determined by self-regulation via stellar feedback. Feedback reduces SFRs and produces reservoirs of gas that lead to rising late-time star formation histories, significantly different from halo accretion histories. Feedback also produces large short-time-scale variability in galactic SFRs, especially in dwarfs. These properties are not captured by common 'sub-grid' wind models.",
"doi": "10.1093/mnras/stu1738",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2014-11-21",
"series_number": "1",
"volume": "445",
"issue": "1",
"pages": "581-603"
},
{
"id": "authors:rvbgq-kaw62",
"collection": "authors",
"collection_id": "rvbgq-kaw62",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141016-110040581",
"type": "article",
"title": "No More Active Galactic Nuclei in Clumpy Disks Than in Smooth Galaxies at z~2 in CANDELS/3D-HST",
"author": [
{
"family_name": "Trump",
"given_name": "Jonathan R.",
"clpid": "Trump-J-R"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We use CANDELS imaging, 3D-HST spectroscopy, and Chandra X-ray data to investigate if active galactic nuclei (AGNs) are preferentially fueled by violent disk instabilities funneling gas into galaxy centers at 1.3 < z < 2.4. We select galaxies undergoing gravitational instabilities using the number of clumps and degree of patchiness as proxies. The CANDELS visual classification system is used to identify 44 clumpy disk galaxies, along with mass-matched comparison samples of smooth and intermediate morphology galaxies. We note that despite being mass-matched and having similar star formation rates, the smoother galaxies tend to be smaller disks with more prominent bulges compared to the clumpy galaxies. The lack of smooth extended disks is probably a general feature of the z ~ 2 galaxy population, and means we cannot directly compare with the clumpy and smooth extended disks observed at lower redshift. We find that z ~ 2 clumpy galaxies have slightly enhanced AGN fractions selected by integrated line ratios (in the mass-excitation method), but the spatially resolved line ratios indicate this is likely due to extended phenomena rather than nuclear AGNs. Meanwhile, the X-ray data show that clumpy, smooth, and intermediate galaxies have nearly indistinguishable AGN fractions derived from both individual detections and stacked non-detections. The data demonstrate that AGN fueling modes at z ~ 1.85\u2014whether violent disk instabilities or secular processes\u2014are as efficient in smooth galaxies as they are in clumpy galaxies.",
"doi": "10.1088/0004-637X/793/2/101",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2014-10-01",
"series_number": "2",
"volume": "793",
"issue": "2",
"pages": "Art. No. 101"
},
{
"id": "authors:j5kbw-wy902",
"collection": "authors",
"collection_id": "j5kbw-wy902",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140602-065803046",
"type": "article",
"title": "Morphologies of z \u223c 0.7 AGN host galaxies in CANDELS: no trend of merger incidence with AGN luminosity",
"author": [
{
"family_name": "Villforth",
"given_name": "C.",
"clpid": "Villforth-C"
},
{
"family_name": "Hopkins",
"given_name": "P. F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "The processes that trigger active galactic nuclei (AGN) remain poorly understood. While lower luminosity AGN may be triggered by minor disturbances to the host galaxy, stronger disturbances are likely required to trigger luminous AGN. Major wet mergers of galaxies are ideal environments for AGN triggering since they provide large gas supplies and galaxy scale torques. There is however little observational evidence for a strong connection between AGN and major mergers. We analyse the morphological properties of AGN host galaxies as a function of AGN and host galaxy luminosity and compare them to a carefully matched sample of control galaxies. AGN are X-ray selected in the redshift range 0.5 < z < 0.8 and have luminosities 41 \u2272 log\u2009(L_X [erg s^(\u22121)]) \u2272 44.5. 'Fake AGN' are simulated in the control galaxies by adding point sources with the magnitude of the matched AGN. We find that AGN host and control galaxies have comparable asymmetries, S\u00e9rsic indices and ellipticities at rest frame \u223c950 nm. AGN host galaxies show neither higher average asymmetries nor higher fractions of very disturbed objects. There is no increase in the prevalence of merger signatures with AGN luminosity. At 95\u2009per\u2009cent confidence we find that major mergers are responsible for <6\u2009per\u2009cent of all AGN in our sample as well as <40\u2009per\u2009cent of the highest luminosity AGN (log\u2009 (L_X [erg s^(\u22121)]) \u223c 43.5). Major mergers therefore either play only a very minor role in the triggering of AGN in the luminosity range studied or time delays are too long for merger features to remain visible.",
"doi": "10.1093/mnras/stu173",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2014-04",
"series_number": "4",
"volume": "439",
"issue": "4",
"pages": "3342-3356"
},
{
"id": "authors:x5ymv-6gj52",
"collection": "authors",
"collection_id": "x5ymv-6gj52",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140313-103344090",
"type": "article",
"title": "The AGORA High-resolution Galaxy Simulations Comparison Project",
"author": [
{
"family_name": "Kim",
"given_name": "Ji-Hoon",
"clpid": "Kim-Ji-Hoon"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"literal": "AGORA Collaboration"
}
],
"abstract": "We introduce the Assembling Galaxies Of Resolved Anatomy (AGORA) project, a comprehensive numerical study of well-resolved galaxies within the \u039bCDM cosmology. Cosmological hydrodynamic simulations with force resolutions of ~100 proper pc or better will be run with a variety of code platforms to follow the hierarchical growth, star formation history, morphological transformation, and the cycle of baryons in and out of eight galaxies with halo masses M_(vir) \u2243 10^(10), 10^(11), 10^(12), and 10^(13) M_\u2609 at z = 0 and two different (\"violent\" and \"quiescent\") assembly histories. The numerical techniques and implementations used in this project include the smoothed particle hydrodynamics codes GADGET and GASOLINE, and the adaptive mesh refinement codes ART, ENZO, and RAMSES. The codes share common initial conditions and common astrophysics packages including UV background, metal-dependent radiative cooling, metal and energy yields of supernovae, and stellar initial mass function. These are described in detail in the present paper. Subgrid star formation and feedback prescriptions will be tuned to provide a realistic interstellar and circumgalactic medium using a non-cosmological disk galaxy simulation. Cosmological runs will be systematically compared with each other using a common analysis toolkit and validated against observations to verify that the solutions are robust\u2014i.e., that the astrophysical assumptions are responsible for any success, rather than artifacts of particular implementations. The goals of the AGORA project are, broadly speaking, to raise the realism and predictive power of galaxy simulations and the understanding of the feedback processes that regulate galaxy \"metabolism.\" The initial conditions for the AGORA galaxies as well as simulation outputs at various epochs will be made publicly available to the community. The proof-of-concept dark-matter-only test of the formation of a galactic halo with a z = 0 mass of M_(vir) \u2243 1.7 \u00d7 10^(11) M_\u2609 by nine different versions of the participating codes is also presented to validate the infrastructure of the project.",
"doi": "10.1088/0067-0049/210/1/14",
"issn": "0067-0049",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Supplement Series",
"publication_date": "2014-01",
"series_number": "1",
"volume": "210",
"issue": "1",
"pages": "Art. No. 14"
},
{
"id": "authors:zczmj-1fv18",
"collection": "authors",
"collection_id": "zczmj-1fv18",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131101-113927261",
"type": "article",
"title": "Turbulent Disks are Never Stable: Fragmentation and Turbulence-promoted Planet Formation",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Christiansen",
"given_name": "Jessie L.",
"orcid": "0000-0002-8035-4778",
"clpid": "Christiansen-J-L"
}
],
"abstract": "A fundamental assumption in our understanding of disks is that when the Toomre Q \u226b 1, the disk is stable against fragmentation into self-gravitating objects (and so cannot form planets via direct collapse). But if disks are turbulent, this neglects a spectrum of stochastic density fluctuations that can produce rare, high-density mass concentrations. Here, we use a recently developed analytic framework to predict the statistics of these fluctuations, i.e., the rate of fragmentation and mass spectrum of fragments formed in a turbulent Keplerian disk. Turbulent disks are never completely stable: we calculate the (always finite) probability of forming self-gravitating structures via stochastic turbulent density fluctuations in such disks. Modest sub-sonic turbulence above Mach number M ~ 0.1 can produce a few stochastic fragmentation or \"direct collapse\" events over ~Myr timescales, even if Q \u226b 1 and cooling is slow (t_cool \u226b t_orbit). In transsonic turbulence this extends to Q ~ 100. We derive the true Q-criterion needed to suppress such events, which scales exponentially with Mach number. We specify to turbulence driven by magneto-rotational instability, convection, or spiral waves and derive equivalent criteria in terms of Q and the cooling time. Cooling times \u2273 50\u2009t_dyn may be required to completely suppress fragmentation. These gravo-turbulent events produce mass spectra peaked near ~(Q\u2009M_disk/M*)^(2)\u2009M_disk (rocky-to-giant planet masses, increasing with distance from the star). We apply this to protoplanetary disk models and show that even minimum-mass solar nebulae could experience stochastic collapse events, provided a source of turbulence.",
"doi": "10.1088/0004-637X/776/1/48",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2013-10-10",
"series_number": "1",
"volume": "776",
"issue": "1",
"pages": "Art. No. 48"
},
{
"id": "authors:qp7a4-fyj86",
"collection": "authors",
"collection_id": "qp7a4-fyj86",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200522-113948620",
"type": "article",
"title": "Feedback-regulated star formation in molecular clouds and galactic discs",
"author": [
{
"family_name": "Faucher-Gigu\u00e8re",
"given_name": "Claude-Andr\u00e9",
"orcid": "0000-0002-4900-6628",
"clpid": "Faucher-Gigu\u00e8re-C-A"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We present a two-zone theory for feedback-regulated star formation in galactic discs, consistently connecting the galaxy-averaged star formation law with star formation proceeding in giant molecular clouds (GMCs). Our focus is on galaxies with gas surface density \u03a3_g \u2273 100 M_\u2299 pc\u207b\u00b2, where the interstellar medium (ISM) can be assumed to be fully molecular. This regime includes most star formation in the Universe and our basic framework can be extended to other galaxies. In our theory, the galactic disc consists of Toomre-mass GMCs embedded in a volume-filling ISM. Radiation pressure on dust disperses GMCs and most supernovae explode in the volume-filling medium. A galaxy-averaged star formation law is derived by balancing the momentum input from supernova feedback with the vertical gravitational weight of the disc gas. This star formation law is in good agreement with observations for a CO conversion factor depending continuously on \u03a3g. We argue that the galaxy-averaged star formation efficiency per free-fall time, \u03f5\u1d4d\u1d43\u02e1_(ff)\u2060, is only a weak function of the efficiency with which GMCs convert their gas into stars, \u03f5^(GMC)_(int)\u2060. This is possible because the rate limiting step for star formation is the rate at which GMCs form: for large efficiency of star formation in GMCs, the Toomre Q parameter obtains a value slightly above unity so that the GMC formation rate is consistent with the galaxy-averaged star formation law. We contrast our results with other theories of turbulence-regulated star formation and discuss predictions of our model. Using a compilation of data from the literature, we show that the galaxy-averaged star formation efficiency per free-fall time is non-universal and increases with increasing gas fraction, as predicted by our model. We also predict that the fraction of the disc gas mass in bound GMCs decreases for increasing values of the GMC star formation efficiency. This is qualitatively consistent with the smooth molecular gas distribution inferred in local ultraluminous infrared galaxies and the small mass fraction in giant clumps in high-redshift galaxies.",
"doi": "10.1093/mnras/stt866",
"issn": "1365-2966",
"publisher": "Oxford University Press",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2013-08-11",
"series_number": "3",
"volume": "433",
"issue": "3",
"pages": "1970-1990"
},
{
"id": "authors:w626h-35b57",
"collection": "authors",
"collection_id": "w626h-35b57",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200522-113948888",
"type": "article",
"title": "Why is the Milky Way X-factor constant?",
"author": [
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "The CO\u2013H\u2082 conversion factor (X_(CO); otherwise known as the X-factor) is observed to be remarkably constant in the Milky Way and in the Local Group (aside from the Small Magellanic Cloud). To date, our understanding of why X_(CO) should be so constant remains poor. Using a combination of extremely high-resolution (\u223c1 pc) galaxy evolution simulations and molecular line radiative transfer calculations, we suggest that XCO displays a narrow range of values in the Galaxy due to the fact that molecular clouds share very similar physical properties. In our models, this is itself a consequence of stellar feedback competing against gravitational collapse. Giant molecular clouds (GMCs) whose lifetimes are regulated by radiative feedback show a narrow range of surface densities, temperatures and velocity dispersions with values comparable to those seen in the Milky Way. As a result, the X-factors from these clouds show reasonable correspondence with observed data from the Local Group, and a relatively narrow range. On the other hand, feedback-free clouds collapse to surface densities that are larger than those seen in the Galaxy, and hence result in X-factors that are systematically too large compared to the Milky Way's. We conclude that radiative feedback within GMCs can generate cloud properties similar to those observed in the Galaxy, and hence a roughly constant Milky Way X-factor in normal, quiescent clouds.",
"doi": "10.1093/mnras/stt784",
"issn": "1365-2966",
"publisher": "Oxford University Press",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2013-08-01",
"series_number": "2",
"volume": "433",
"issue": "2",
"pages": "1223-1229"
},
{
"id": "authors:mj7tc-bvk05",
"collection": "authors",
"collection_id": "mj7tc-bvk05",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200522-113948718",
"type": "article",
"title": "Variations in the stellar CMF and IMF: from bottom to top",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We use a recently developed analytic model for the interstellar medium (ISM) structure from scales of giant molecular clouds (GMCs) through star-forming cores to explore how the pre-stellar core mass function (CMF) and, by extrapolation, stellar initial mass function (IMF) should depend on both local and galactic properties. If the ISM is supersonically turbulent, the statistical properties of the density field follow from the turbulent velocity spectrum, and the excursion set formalism can be applied to analytically calculate the mass function of collapsing cores on the smallest scales on which they are self-gravitating (non-fragmenting). Two parameters determine the model: the disc-scale Mach number M_h (which sets the shape of the CMF) and the absolute velocity/surface density (to assign an absolute scale). We show that, for normal variation in disc properties and gas temperatures in cores in the Milky Way and local galaxies, there is almost no variation in the high-mass behaviour of the CMF/IMF. The slope is always close to Salpeter down to \u2272 1\u2009M_\u2299. We predict modest variation in the sub-solar regime, mostly from variation in M_h\u2060, but this is consistent with the \u223c1\u03c3 observed scatter in sub-solar IMFs in local regions. For fixed global (galaxy) properties, there is little variation in shape or 'upper mass limit' with parent GMC mass or density. However, in extreme starbursts \u2013 ultra-luminous infrared galaxies (ULIRGs) and merging galaxy nuclei \u2013 we predict a bottom-heavy CMF. This agrees well with the IMF recently inferred for the centres of Virgo ellipticals, believed to have formed in such a process. The CMF is bottom heavy despite the gas temperature being an order of magnitude larger, because M_h is also much larger. Larger M_h values make the 'parent' cloud mass (the turbulent Jeans mass) larger, but promote fragmentation to smaller scales (set by the sonic mass, not the Jeans mass); this shifts the turnover mass and also steepens the slope of the low-mass CMF. The model may also predict a top-heavy CMF for the in situ star formation in the sub-pc disc around Sgr A*, but the relevant input parameters are uncertain.",
"doi": "10.1093/mnras/stt713",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2013-07-21",
"series_number": "1",
"volume": "433",
"issue": "1",
"pages": "170-177"
},
{
"id": "authors:nce0m-x3q77",
"collection": "authors",
"collection_id": "nce0m-x3q77",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200522-113948802",
"type": "article",
"title": "Dense molecular gas: a sensitive probe of stellar feedback models",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-D"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
}
],
"abstract": "We show that the mass fraction of giant molecular cloud (GMC) gas (n \u2273 100\u2009cm\u207b\u00b3) in dense (n \u226b 10\u2074\u2009cm\u207b\u00b3) star-forming clumps, observable in dense molecular tracers (L_(HCN)/L_(CO(1\u20130))), is a sensitive probe of the strength and mechanism(s) of stellar feedback, as well as the star formation efficiencies in the most dense gas. Using high-resolution galaxy-scale simulations with pc-scale resolution and explicit models for feedback from radiation pressure, photoionization heating, stellar winds and supernovae (SNe), we make predictions for the dense molecular gas tracers as a function of GMC and galaxy properties and the efficiency of stellar feedback/star formation. In models with weak/no feedback, much of the mass in GMCs collapses into dense subunits, predicting L_(HCN)/L_(CO(1\u20130)) ratios order-of-magnitude larger than observed. By contrast, models with feedback properties taken directly from stellar evolution calculations predict dense gas tracers in good agreement with observations. Changing the strength or timing of SNe tends to move systems along, rather than off, the L_(HCN)\u2013L_(CO) relation (because SNe heat lower density material, not the high-density gas). Changing the strength of radiation pressure (which acts efficiently in the highest density gas), however, has a much stronger effect on L_(HCN) than on L_(CO). We show that degeneracies between the strength of feedback, and efficiency of star formation on small scales, can be broken by the combination of dense gas, intermediate-density gas and total star formation rate (SFR) tracers, and favour models where the galaxy-integrated star formation efficiency in dense gas is low. We also predict that the fraction of dense gas (_(LHCN)/L_(CO(1\u20130))) increases with increasing GMC surface density; this drives a trend in L_(HCN)/L_(CO(1\u20130)) with SFR and luminosity which has tentatively been observed. Our results make specific predictions for enhancements in the dense gas tracers in unusually dense environments such as ultraluminous infrared galaxies and galactic nuclei (including the galactic centre).",
"doi": "10.1093/mnras/stt688",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2013-07-21",
"series_number": "1",
"volume": "433",
"issue": "1",
"pages": "69-77"
},
{
"id": "authors:pke31-g2v42",
"collection": "authors",
"collection_id": "pke31-g2v42",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130807-131742868",
"type": "article",
"title": "The meaning and consequences of star formation criteria in galaxy models with resolved stellar feedback",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-D"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N"
}
],
"abstract": "We consider the effects of different criteria for determining where stars will form in gas on galactic scales, in simulations with high (1 pc) resolution, with explicitly resolved physics of Giant Molecular Cloud (GMC) formation and destruction, and stellar feedback from supernovae, radiation pressure, stellar winds and photoheating. We compare: (1) a self-gravity criterion (based on the local virial parameter and the assumption that self-gravitating gas collapses to high density in a single free-fall time), (2) a fixed density threshold, (3) a molecular-gas law, (4) a temperature threshold, (5) a requirement that the gas be Jeans unstable, (6) a criteria that cooling times be shorter than dynamical times and (7) a convergent-flow criterion. We consider all of these in both a Milky Way (MW)-like and high-density (starburst or high-redshift) galaxy. With feedback present, all models produce identical integrated star formation rates (SFRs), in good agreement with the Kennicutt relation; without feedback all produce orders-of-magnitude excessive SFRs. This is totally dependent on feedback and independent of the star formation (SF) law, even if the 'local' collapse efficiency is 100\u2009per\u2009cent. However, the predicted spatial and density distribution depend strongly on the SF criteria. Because cooling rates are generally fast within galaxy discs, and gas is turbulent, criteria (4)\u2013(7) are very 'weak' and spread the SF uniformly over most of the disc (down to densities n \u223c 0.01\u20130.1\u2009cm^\u22123). A molecular criterion (3) localizes to slightly higher densities, but still a wide range; for metallicity near solar, it is almost identical to a fixed density threshold at n \u223c 1\u2009cm^\u22123 (well below the mean density in the central MW or starburst systems). A fixed density threshold (2) can always select the highest resolved densities, but must be adjusted both for simulation resolution and individual galaxy properties \u2013 the same threshold that works well in a MW-like simulation will select nearly all gas in a starburst. Binding criteria (1) tend to adaptively select the largest local overdensities, independent of galaxy model or resolution, and automatically predict clustered SF. We argue that this SF model (possible with other secondary criteria) is most physically motivated and presents significant numerical advantages in simulations with a large dynamic range.",
"doi": "10.1093/mnras/stt723",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2013-07-11",
"series_number": "4",
"volume": "432",
"issue": "4",
"pages": "2647-2653"
},
{
"id": "authors:dmarp-wak18",
"collection": "authors",
"collection_id": "dmarp-wak18",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130805-101243638",
"type": "article",
"title": "Accretion does not drive the turbulence in galactic discs",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N"
}
],
"abstract": "Rapid accretion of cold intergalactic gas plays a crucial role in getting gas into galaxies. It has been suggested that this gas accretion proceeds along narrow streams that might also directly drive the turbulence in galactic gas, dynamical disturbances and bulge formation. In cosmological simulations, however, it is impossible to isolate and hence disentangle the effect of cold stream accretion from internal instabilities and mergers. Moreover, in most current cosmological simulations, the phase structure and turbulence in the interstellar medium (ISM) arising from stellar feedback are treated in an approximate (subgrid) manner, so that the feedback cannot generate turbulence in the ISM. In this paper we therefore test the effects of cold streams in extremely high-resolution simulations of otherwise isolated galaxy discs using detailed models for star formation and stellar feedback; we then include or exclude mock cold flows falling on to the galaxies, with mass accretion rates, velocities and flow geometry set to maximize their effect on the gaseous disc. We find (1) turbulent velocity dispersions in gas discs are identical with or without the presence of the cold flow; the energy injected by the flow is efficiently dissipated where it meets the disc. (2) In runs without stellar feedback, the presence of a cold flow has essentially no effect on runaway fragmentation (local collapse), resulting in star formation rates (SFRs) that are an order-of-magnitude too large. (3) Model discs in runs with both explicit feedback and cold flows have higher SFRs, but only insofar as they have more gas. (4) Because the flows are extended, relative to the size of the disc, they do not trigger strong resonant responses and so induce weak gross morphological perturbation (bulge formation via instabilities/fragmentation is not accelerated). (5) However, flows can thicken the disc by direct contribution of out-of-plane or misaligned star-forming streams/filaments. We conclude that while inflows are critical over cosmological time-scales to determine the supply and angular momentum of gas discs, they have weak instantaneous dynamical effects on galaxies.",
"doi": "10.1093/mnras/stt472",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2013-07-11",
"series_number": "4",
"volume": "432",
"issue": "4",
"pages": "2639-2646"
},
{
"id": "authors:4da28-zah59",
"collection": "authors",
"collection_id": "4da28-zah59",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130923-104112297",
"type": "article",
"title": "Resolving the generation of starburst winds in Galaxy mergers",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
},
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-D"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
}
],
"abstract": "We study galaxy superwinds driven in major mergers, using pc-scale resolution simulations with detailed models for stellar feedback that can self-consistently follow the generation of winds. The models include molecular cooling, star formation at high densities in giant molecular clouds, and gas recycling and feedback from supernovae (I and II), stellar winds and radiation pressure. We study mergers of systems from Small-Magellanic-Cloud-like dwarfs and Milky Way analogues to z \u223c 2 starburst discs. Multiphase superwinds are generated in all passages, with outflow rates up to \u223c1000\u2009M\u2299\u2009yr^(\u22121). However, the wind mass-loading efficiency (outflow rate divided by star formation rate, SFR) is similar to that in the isolated galaxy counterparts of each merger: it depends more on global galaxy properties (mass, size and escape velocity) than on the dynamical state or orbital parameters of the merger. Winds tend to be bi- or unipolar, but multiple 'events' build up complex morphologies with overlapping, differently oriented bubbles and shells at a range of radii. The winds have complex velocity and phase structure, with material at a range of speeds up to \u223c1000\u2009km\u2009s^(\u22121) (forming a Hubble-like flow), and a mix of molecular, ionized and hot gas that depends on galaxy properties. We examine how these different phases are connected to different feedback mechanisms. These simulations resolve a problem in some 'subgrid' models, where simple wind prescriptions can dramatically suppress merger-induced starbursts, often making it impossible to form Ultra Luminous Infrared Galaxies (ULIRGs). Despite large mass-loading factors (\u227310\u201320) in the winds simulated here, the peak SFRs are comparable to those in 'no wind' simulations. Wind acceleration does not act equally, so cold dense gas can still lose angular momentum and form stars, while these stars blow out gas that would not have participated in the starburst in the first place. Considerable wind material is not unbound, and falls back on the disc at later times post-merger, leading to higher post-starburst SFRs in the presence of stellar feedback. We consider different simulation numerical methods and their effects on the wind phase structure; while most results are converged, we find that the existence of small clumps in the outflow at large distances from the galaxy is quite sensitive to the methodology.",
"doi": "10.1093/mnras/stt690",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2013-07",
"series_number": "1",
"volume": "433",
"issue": "1",
"pages": "78-97"
},
{
"id": "authors:z62ev-tkq05",
"collection": "authors",
"collection_id": "z62ev-tkq05",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130605-082348981",
"type": "article",
"title": "Modeling Mid-infrared Diagnostics of Obscured Quasars and Starbursts",
"author": [
{
"family_name": "Snyder",
"given_name": "Gregory F.",
"clpid": "Snyder-G-F"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Sajina",
"given_name": "Anna",
"orcid": "0000-0002-1917-1200",
"clpid": "Sajina-Anna"
},
{
"family_name": "Jonsson",
"given_name": "Patrik",
"clpid": "Jonsson-P"
},
{
"family_name": "Cox",
"given_name": "Thomas J.",
"clpid": "Cox-T-J"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Yan",
"given_name": "Lin",
"orcid": "0000-0003-1710-9339",
"clpid": "Yan-Lin"
}
],
"abstract": "We analyze the link between active galactic nuclei (AGNs) and mid-infrared flux using dust radiative transfer calculations of starbursts realized in hydrodynamical simulations. Focusing on the effects of galaxy dust, we evaluate diagnostics commonly used to disentangle AGN and star formation in ultraluminous infrared galaxies (ULIRGs). We examine these quantities as a function of time, viewing angle, dust model, AGN spectrum, and AGN strength in merger simulations representing two possible extremes of the ULIRG population: one is a typical gas-rich merger at z ~ 0, and the other is characteristic of extremely obscured starbursts at z ~ 2-4. This highly obscured burst begins star-formation-dominated with significant polycyclic aromatic hydrocarbon (PAH) emission, and ends with a ~10^9 yr period of red near-IR colors. At coalescence, when the AGN is most luminous, dust obscures the near-infrared AGN signature, reduces the relative emission from PAHs, and enhances the 9.7 \u03bcm absorption by silicate grains. Although generally consistent with previous interpretations, our results imply none of these indicators can unambiguously estimate the AGN luminosity fraction in all cases. Motivated by the simulations, we show that a combination of the extinction feature at 9.7 \u03bcm, the PAH strength, and a near-infrared slope can simultaneously constrain the AGN fraction and dust grain distribution for a wide range of obscuration. We find that this indicator, accessible to the James Webb Space Telescope, may estimate the AGN power as tightly as the hard X-ray flux alone, thereby providing a valuable future cross-check and constraint for large samples of distant ULIRGs.",
"doi": "10.1088/0004-637X/768/2/168",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2013-05-10",
"series_number": "2",
"volume": "768",
"issue": "2",
"pages": "Art. No. 168"
},
{
"id": "authors:mv5xa-rps12",
"collection": "authors",
"collection_id": "mv5xa-rps12",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200522-113949119",
"type": "article",
"title": "Star formation in galaxy mergers with realistic models of stellar feedback and the interstellar medium",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Cox",
"given_name": "Thomas J.",
"clpid": "Cox-T-J"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
},
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-D"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
}
],
"abstract": "We use hydrodynamic simulations with detailed, explicit models for stellar feedback to study galaxy mergers. These high-resolution (\u223c1\u2009pc) simulations follow the formation and destruction of individual giant molecular clouds (GMC) and star clusters. We find that the final starburst is dominated by in situ star formation, fuelled by gas which flows inwards due to global torques. The resulting high gas density results in rapid star formation. The gas is self-gravitating, and forms massive (\u227210\u00b9\u2070\u2009M_\u2299) GMC and subsequently super star clusters (with masses up to 10\u2078\u2009M_\u2299). However, in contrast to some recent simulations, the bulk of new stars which eventually form the central bulge are not born in super-clusters which then sink to the centre of the galaxy. This is because feedback efficiently disperses GMC after they turn several\u2009per\u2009cent of their mass into stars. In other words, most of the mass that reaches the nucleus does so in the form of gas. The Kennicutt\u2013Schmidt law emerges naturally as a consequence of feedback balancing gravitational collapse, independent of the small-scale star formation microphysics. The same mechanisms that drive this relation in isolated galaxies, in particular radiation pressure from infrared photons, extend, with no fine-tuning, over seven decades in star formation rate (SFR) to regulate star formation in the most extreme starburst systems with densities \u227310\u2074\u2009M_\u2299\u2009pc\u207b\u00b2. This feedback also drives super-winds with large mass-loss rates; however, a significant fraction of the wind material falls back on to the discs at later times, leading to higher post-starburst SFRs in the presence of stellar feedback. This suggests that strong active galactic nucleus feedback may be required to explain the sharp cut-offs in SFR that are observed in post-merger galaxies. \n\nWe compare the results to those from simulations with no explicit resolution of GMC or feedback ['effective equation-of-state' (EOS) models]. We find that global galaxy properties are similar between EOS and resolved-feedback models. The relic structure and mass profile, and the total mass of stars formed in the nuclear starburst are quite similar, as is the morphological structure during and after mergers (tails, bridges, etc.). Disc survival in sufficiently gas rich mergers is similar in the two cases, and the new models follow the same scalings as derived for the efficiency of disc re-formation after a merger as derived from previous work with the simplified EOS models. While the global galaxy properties are similar between EOS and feedback models, subgalaxy-scale properties and the SFRs can be quite different: the more detailed models exhibit significantly higher star formation in tails and bridges (especially in shocks), and allow us to resolve the formation of super star clusters. In the new models, the star formation is more strongly time-variable and drops more sharply between close passages. The instantaneous burst enhancement can be higher or lower, depending on the details of the orbit and initial structural properties of the galaxies; first-passage bursts are more sensitive to these details than those at the final coalescence.",
"doi": "10.1093/mnras/stt017",
"issn": "1365-2966",
"publisher": "Oxford University Press",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2013-04-11",
"series_number": "3",
"volume": "430",
"issue": "3",
"pages": "1901-1927"
},
{
"id": "authors:gw518-9sy73",
"collection": "authors",
"collection_id": "gw518-9sy73",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200522-113949029",
"type": "article",
"title": "A general theory of turbulent fragmentation",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We develop an analytic framework to understand fragmentation in turbulent, self-gravitating media. In previous work, we showed how some properties of turbulence can be predicted by application of the excursion-set formalism. Here, we generalize this to understand fully time-dependent gravo-turbulent fragmentation and collapse. We show that turbulent systems are always gravitationally unstable in a probabilistic sense. The fragmentation mass spectrum, size\u2013mass\u2013density\u2013linewidth relations of collapsing objects, their correlation functions and clustering, the range of spatial scales over which fragmentation occurs, and the time-dependent rate of collapse/fragmentation (as a function of size/mass) are analytically predictable. We show how these depend on bulk properties of turbulence; fragmentation is promoted at higher Mach numbers and shallower power spectra. We also generalize the model to properly include rotation, complicated gas equations of state, collapsing/expanding backgrounds, magnetic fields, intermittency and non-normal statistics (with inherently correlated fluctuations). This allows us to formally derive how fragmentation is suppressed with 'stiffer' equations of state (e.g. higher polytropic index \u03b3) or differently driven turbulence (solenoidal versus compressive). The suppression appears at an 'effective sonic scale' where bM(R_s,\u03c1_(crit)[R)s]) \u2248 1\u2060, with \u03c1_(crit) being the (scale-dependent) critical density for fragmentation. Gas becomes stable against collapse below this scale for \u03b3 > 4/3; however, fragmentation still occurs on larger scales. We show that the scale-free nature of turbulence and gravity generically drives mass spectra and correlation functions towards universal shapes (observed in a wide variety of astrophysical phenomena), with weak residual dependence on many properties of the media. We find that correlated fluctuations on different scales, non-Gaussian density distributions and intermittency have surprisingly small effects on the fragmentation process. We demonstrate that this is because fragmentation cascades on small scales are generically 'frozen in' when large-scale fluctuations push the 'parent' region above the collapse threshold; though they collapse, their statistics are only weakly modified by the collapse process. Finally, with thermal or turbulent support, structure develops 'top-down' in time via a fragmentation cascade, but we show that significant rotational/angular momentum support reverses the sense of structure formation to 'bottom-up' growth via mergers of bound clumps, and introduces a characteristic 'maximal instability scale' distinct from the Toomre scale.",
"doi": "10.1093/mnras/sts704",
"issn": "1365-2966",
"publisher": "Oxford University Press",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2013-04-11",
"series_number": "3",
"volume": "430",
"issue": "3",
"pages": "1653-1693"
},
{
"id": "authors:hj9yr-eac12",
"collection": "authors",
"collection_id": "hj9yr-eac12",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200522-113949215",
"type": "article",
"title": "A model for (non-lognormal) density distributions in isothermal turbulence",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We propose a new, physically motivated fitting function for density probability distribution functions (PDFs) in turbulent, ideal gas. Although it is generally known that when gas is isothermal, the PDF is approximately lognormal in the core, high-resolution simulations show large deviations from exact lognormality. The proposed function provides an extraordinarily accurate description of the density PDFs in simulations with Mach numbers \u223c0.1\u201315 and dispersion in log\u2009(\u03c1) from \u223c0.01 to 4 dex. Compared to a lognormal or lognormal-skew-kurtosis model, the fits are improved by orders of magnitude in the wings of the distribution (with fewer free parameters). This is true in simulations using a variety of distinct numerical methods, including or excluding magnetic fields. Deviations from lognormality are represented by a parameter T that appears to increase systematically with the compressive Mach number of the simulations. The proposed distribution can be derived from intermittent cascade models of the longitudinal (compressive) velocity differences, which should be directly related to density fluctuations, and we also provide a simple interpretation of the density PDF as the product of a continuous-time relaxation process. As such this parameter T is consistent with the same single parameter needed to explain the (intermittent) velocity structure functions; its behaviour is consistent with turbulence becoming more intermittent as it becomes more dominated by strong shocks. It provides a new and unique probe of the role of intermittency in the density (not just velocity) structure of turbulence. We show that this naturally explains some apparent contradictory results in the literature (for example, in the dispersion\u2013Mach number relation) based on use of different moments of the density PDF, as well as differences based on whether volume-weighted or mass-weighted quantities are measured. We show how these are fundamentally related to the fact that mass conservation requires violations of lognormal statistics.",
"doi": "10.1093/mnras/stt010",
"issn": "1365-2966",
"publisher": "Oxford University Press",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2013-04-11",
"series_number": "3",
"volume": "430",
"issue": "3",
"pages": "1880-1891"
},
{
"id": "authors:rkkg0-29r97",
"collection": "authors",
"collection_id": "rkkg0-29r97",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200522-113949466",
"type": "article",
"title": "A general class of Lagrangian smoothed particle hydrodynamics methods and implications for fluid mixing problems",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Various formulations of smoothed particle hydrodynamics (SPH) have been proposed, intended to resolve certain difficulties in the treatment of fluid mixing instabilities. Most have involved changes to the algorithm which either introduces artificial correction terms or violates what is arguably the greatest advantage of SPH over other methods: manifest conservation of energy, entropy, momentum and angular momentum. Here, we show how a class of alternative SPH equations of motion (EOM) can be derived self-consistently from a discrete particle Lagrangian \u2013 guaranteeing manifest conservation \u2013 in a manner which tremendously improves treatment of these instabilities and contact discontinuities. Saitoh & Makino recently noted that the volume element used to discretize the EOM does not need to explicitly invoke the mass density (as in the 'standard' approach); we show how this insight, and the resulting degree of freedom, can be incorporated into the rigorous Lagrangian formulation that retains ideal conservation properties and includes the '\u2207h' terms that account for variable smoothing lengths. We derive a general EOM for any choice of volume element (particle 'weights') and method of determining smoothing lengths. We then specify this to a 'pressure\u2013entropy formulation' which resolves problems in the traditional treatment of fluid interfaces. Implementing this in a new version of the GADGET code, we show it leads to good performance in mixing experiments (e.g. Kelvin\u2013Helmholtz and 'blob' tests). And conservation is maintained even in strong shock/blastwave tests, where formulations without manifest conservation produce large errors. This also improves the treatment of subsonic turbulence and lessens the need for large kernel particle numbers. The code changes are trivial and entail no additional numerical expense. This provides a general framework for self-consistent derivation of different 'flavours' of SPH.",
"doi": "10.1093/mnras/sts210",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2013-02-01",
"series_number": "4",
"volume": "428",
"issue": "4",
"pages": "2840-2856"
},
{
"id": "authors:n5bxr-gbr35",
"collection": "authors",
"collection_id": "n5bxr-gbr35",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200522-113949381",
"type": "article",
"title": "Why do stars form in clusters? An analytic model for stellar correlation functions",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Recently, we have shown that if the interstellar medium is governed by supersonic turbulent flows, the excursion-set formalism can be used to calculate the statistics of self-gravitating objects over a wide range of scales. On the largest self-gravitating scales ('first crossing'), these correspond to giant molecular clouds (GMCs), and on the smallest non-fragmenting self-gravitating scales ('last crossing'), to protostellar cores. Here, we extend this formalism to rigorously calculate the autocorrelation and cross-correlation functions of cores (and by extension, young stars) as a function of spatial separation and mass, in analogy to the cosmological calculation of halo clustering. We show that this generically predicts that star formation is very strongly clustered on small scales: stars form in clustered regions, themselves inside GMCs. Outside the binary-star regime, the projected correlation function declines as a weak power law, until a characteristic scale which corresponds to the characteristic mass scale of GMCs. On much larger scales the clustering declines such that star formation is not strongly biased on galactic scales, relative to the actual dense gas distribution. The precise correlation function shape depends on properties of the turbulent spectrum, but its qualitative behaviour is quite general. The predictions agree well with observations of young star and core autocorrelation functions over \u223c4 dex in radius. Clustered star formation is a generic consequence of supersonic turbulence if most of the power in the velocity field, hence the contribution to density fluctuations, comes from large scales \u223ch. The distribution of self-gravitating masses near the sonic length is then imprinted by fluctuations on larger scales. We similarly show that the fraction of stars formed in 'isolated' modes should be small, \u227210 per cent.",
"doi": "10.1093/mnras/sts147",
"issn": "1365-2966",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2013-01-21",
"series_number": "3",
"volume": "428",
"issue": "3",
"pages": "1950-1957"
},
{
"id": "authors:cbftc-xgp68",
"collection": "authors",
"collection_id": "cbftc-xgp68",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200522-113949570",
"type": "article",
"title": "Submillimetre galaxies in a hierarchical universe: number counts, redshift distribution and implications for the IMF",
"author": [
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-D"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Jonsson",
"given_name": "Patrik",
"clpid": "Jonsson-Patrik"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Cox",
"given_name": "T. J.",
"clpid": "Cox-T-J"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
}
],
"abstract": "High-redshift submillimetre galaxies (SMGs) are some of the most rapidly star-forming galaxies in the Universe. Historically, galaxy formation models have had difficulty explaining the observed number counts of SMGs. We combine a semi-empirical model with 3D hydrodynamical simulations and 3D dust radiative transfer to predict the number counts of unlensed SMGs. Because the stellar mass functions, gas and dust masses, and sizes of our galaxies are constrained to match observations, we can isolate uncertainties related to the dynamical evolution of galaxy mergers and the dust radiative transfer. The number counts and redshift distributions predicted by our model agree well with observations. Isolated disc galaxies dominate the faint (S_(1.1) \u2272 1 or S_(850) \u2272 2 mJy) population. The brighter sources are a mix of merger-induced starbursts and galaxy-pair SMGs; the latter subpopulation accounts for \u223c30\u201350 per cent of all SMGs at all S_(1.1) \u2273 0.5 mJy (S_(850) \u2273 1 mJy). The mean redshifts are \u223c3.0\u20133.5, depending on the flux cut, and the brightest sources tend to be at higher redshifts. Because the galaxy-pair SMGs will be resolved into multiple fainter sources by the Atacama Large Millimeter/submillimeter Array (ALMA), the bright ALMA counts should be as much as two times less than those observed using single-dish telescopes. The agreement between our model, which uses a Kroupa initial mass function (IMF), and observations suggests that the IMF in high-redshift starbursts need not be top heavy; if the IMF were top heavy, our model would overpredict the number counts. We conclude that the difficulty some models have reproducing the observed SMG counts is likely indicative of more general problems \u2013 such as an underprediction of the abundance of massive galaxies or a star formation rate and stellar mass relation normalization lower than that observed \u2013 rather than a problem specific to the SMG population.",
"doi": "10.1093/mnras/sts222",
"issn": "1365-2966",
"publisher": "Oxford University Press (OUP)",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2013-01-21",
"series_number": "3",
"volume": "428",
"issue": "3",
"pages": "2529-2547"
},
{
"id": "authors:cpxzj-hjb15",
"collection": "authors",
"collection_id": "cpxzj-hjb15",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200522-113949298",
"type": "article",
"title": "Stellar feedback and bulge formation in clumpy discs",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
}
],
"abstract": "We use numerical simulations of isolated galaxies to study the effects of stellar feedback on the formation and evolution of giant star-forming gas 'clumps' in high-redshift, gas-rich galaxies. Such galactic discs are unstable to the formation of bound gas-rich clumps whose properties initially depend only on global disc properties, not the microphysics of feedback. In simulations without stellar feedback, clumps turn an order-unity fraction of their mass into stars and sink to the centre, forming a large bulge and kicking most of the stars out into a much more extended stellar envelope. By contrast, strong radiative stellar feedback disrupts even the most massive clumps after they turn \u223c10\u201320 per cent of their mass into stars, in a time-scale of \u223c10\u2013100 Myr, ejecting some material into a superwind and recycling the rest of the gas into the diffuse interstellar medium (ISM). This suppresses the bulge formation rate by direct 'clump coalescence' by a factor of several. However, the galactic discs do undergo significant internal evolution in the absence of mergers: clumps form and disrupt continuously and torque gas to the galactic centre. The resulting evolution is qualitatively similar to bar/spiral evolution in simulations with a more homogeneous ISM.",
"doi": "10.1111/j.1365-2966.2012.21981.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2012-12-01",
"series_number": "2",
"volume": "427",
"issue": "2",
"pages": "968-978"
},
{
"id": "authors:ae63e-gs705",
"collection": "authors",
"collection_id": "ae63e-gs705",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200601-143024713",
"type": "article",
"title": "Why are active galactic nuclei and host galaxies misaligned?",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-D"
}
],
"abstract": "It is well established observationally that the characteristic angular momentum axis on small scales around active galactic nuclei (AGN), traced by radio jets and the putative torus, is not well correlated with the large-scale angular momentum axis of the host galaxy. In this paper, we show that such misalignments arise naturally in high-resolution simulations in which we follow angular momentum transport and inflows from galaxy to sub-pc scales near AGN, triggered either during galaxy mergers or by instabilities in isolated discs. Sudden misalignments can sometimes be caused by single massive clumps falling into the centre slightly off-axis, but more generally, they arise even when the gas inflows are smooth and trace only global gravitational instabilities. When several nested, self-gravitating modes are present, the inner ones can precess and tumble in the potential of the outer modes. Resonant angular momentum exchange can flip or re-align the spin of an inner mode on a short time-scale, even without the presence of massive clumps. We therefore do not expect that AGN and their host galaxies will be preferentially aligned, nor should the relative alignment be an indicator of the AGN fuelling mechanism. We discuss implications of this conclusion for AGN feedback and black hole (BH) spin evolution. The misalignments may mean that even BHs accreting from smooth large-scale discs will not be spun up to maximal rotation and so have more modest radiative efficiencies and inefficient jet formation. Even more random orientations/lower spins are possible if there is further unresolved clumpiness in the gas, and more ordered accretion may occur if the inflow is slower and not self-gravitating.",
"doi": "10.1111/j.1365-2966.2012.21449.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2012-09-11",
"series_number": "2",
"volume": "425",
"issue": "2",
"pages": "1121-1128"
},
{
"id": "authors:mx2ac-gy267",
"collection": "authors",
"collection_id": "mx2ac-gy267",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200601-143024831",
"type": "article",
"title": "The stellar initial mass function, core mass function and the last-crossing distribution",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "Hennebelle & Chabrier attempted to derive the stellar initial mass function (IMF) as a consequence of lognormal density fluctuations in a turbulent medium, using an argument similar to Press & Schechter for Gaussian random fields. Like that example, however, the solution there does not resolve the 'cloud-in-cloud' problem; it also does not extend to the large scales that dominate the velocity and density fluctuations. In principle, these can change the results at the order-of-magnitude level or more. In this paper, we use the results from Hopkins to generalize the excursion set formalism and derive the exact solution in this regime. We argue that the stellar IMF and core mass function (CMF) should be associated with the last-crossing distribution, i.e. the mass spectrum of bound objects defined on the smallest scale on which they are self-gravitating. This differs from the first-crossing distribution (mass function on the largest self-gravitating scale) which is defined in cosmological applications and which, Hopkins shows, corresponds to the giant molecular cloud (GMC) mass function in discs. We derive an analytic equation for the last-crossing distribution that can be applied for an arbitrary collapse threshold shape in interstellar medium and cosmological studies. With this, we show that the same model that predicts the GMC mass function and large-scale structure of galaxy discs also predicts the CMF \u2013 and by extrapolation stellar IMF \u2013 in good agreement with observations. The only adjustable parameter in the model is the turbulent velocity power spectrum, which in the range p \u2248 5/3-2 gives similar results. We also use this to formally justify why the approximate solution in Hennebelle & Chabrier is reasonable (up to a normalization constant) over the mass range of the CMF/IMF; however, there are significant corrections at intermediate and high masses. We discuss how the exact solutions here can be used to predict additional quantities such as the clustering of stars, and embedded into time-dependent models that follow density fluctuations, fragmentation, mergers and successive generations of star formation.",
"doi": "10.1111/j.1365-2966.2012.20731.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2012-07-01",
"series_number": "3",
"volume": "423",
"issue": "3",
"pages": "2037-2044"
},
{
"id": "authors:5j5s8-2pq62",
"collection": "authors",
"collection_id": "5j5s8-2pq62",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200601-143024924",
"type": "article",
"title": "An excursion-set model for the structure of giant molecular clouds and the interstellar medium",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "The interstellar medium (ISM) is governed by supersonic turbulence on a range of scales. We use this simple fact to develop a rigorous excursion-set model for the formation, structure and time evolution of dense gas structures [e.g. giant molecular clouds (GMCs), massive clumps and cores]. Supersonic turbulence drives the density distribution in non-self-gravitating regions to a lognormal with dispersion increasing with Mach number. We generalize this to include scales \u2273 h (the disc scale-height), and use it to construct the statistical properties of the density field smoothed on a scale R . We then compare conditions for self-gravitating collapse including thermal, turbulent and rotational (disc shear) support (reducing to the Jeans/Toomre criterion on small/large scales). We show that this becomes a well-defined barrier crossing problem. As such, an exact 'bound object mass function' can be derived, from scales of the sonic length to well above the disc Jeans mass. This agrees remarkably well with observed GMC mass functions in the Milky Way and other galaxies, with the only inputs being the total mass and size of the galaxies (to normalize the model). This explains the cut-off of the mass function and its power-law slope (close to, but slightly shallower than, \u22122). The model also predicts the linewidth\u2013size and size\u2013mass relations of clouds and the dependence of residuals from these relations on mean surface density/pressure, in excellent agreement with observations. We use this to predict the spatial correlation function/clustering of clouds and, by extension, star clusters; these also agree well with observations. We predict the size/mass function of 'bubbles' or 'holes' in the ISM, and show that this can account for the observed H I hole distribution without requiring any local feedback/heating sources. We generalize the model to construct time-dependent 'merger/fragmentation trees' which can be used to follow cloud evolution and construct semi-analytic models for the ISM, GMCs and star-forming populations. We provide explicit recipes to construct these trees. We use a simple example to show that if clouds are not destroyed in \u223c1\u20135 crossing times, then all the ISM mass would be trapped in collapsing objects even if the large-scale turbulent cascade were maintained.",
"doi": "10.1111/j.1365-2966.2012.20730.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2012-07-01",
"series_number": "3",
"volume": "423",
"issue": "3",
"pages": "2016-2036"
},
{
"id": "authors:m6426-4vj92",
"collection": "authors",
"collection_id": "m6426-4vj92",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200601-143025126",
"type": "article",
"title": "Stellar feedback in galaxies and the origin of galaxy-scale winds",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
}
],
"abstract": "Feedback from massive stars is believed to play a critical role in driving galactic super\u2010winds that enrich the intergalactic medium and shape the galaxy mass function, mass\u2013metallicity relation and other global galaxy properties. In previous papers, we have introduced new numerical methods for implementing stellar feedback on sub\u2010giant molecular cloud (sub\u2010GMC) through galactic scales in numerical simulations of galaxies; the key physical processes include radiation pressure in the ultraviolet through infrared, supernovae (Type I and Type II), stellar winds ('fast' O star through 'slow' asymptotic giant branch winds), and H\u2003II photoionization. Here, we show that these feedback mechanisms drive galactic winds with outflow rates as high as \u223c10\u201320 times the galaxy star formation rate. The mass\u2010loading efficiency (wind mass\u2010loss rate divided by the star formation rate) scales roughly as \u1e40_(wind)/\u1e40\u2605 \u221d V_c\u207b\u00b9 (where V_c is the galaxy circular velocity), consistent with simple momentum\u2010conservation expectations. We use our suite of simulations to study the relative contribution of each feedback mechanism to the generation of galactic winds in a range of galaxy models, from Small Magellanic Cloud like dwarfs and Milky Way (MW) analogues to z\u223c 2 clumpy discs. In massive, gas\u2010rich systems (local starbursts and high\u2010z galaxies), radiation pressure dominates the wind generation. By contrast, for MW\u2010like spirals and dwarf galaxies the gas densities are much lower and sources of shock\u2010heated gas such as supernovae and stellar winds dominate the production of large\u2010scale outflows. In all of our models, however, the winds have a complex multiphase structure that depends on the interaction between multiple feedback mechanisms operating on different spatial scales and time\u2010scales: any single feedback mechanism fails to reproduce the winds observed. We use our simulations to provide fitting functions to the wind mass loading and velocities as a function of galaxy properties, for use in cosmological simulations and semi\u2010analytic models. These differ from typically adopted formulae with an explicit dependence on the gas surface density that can be very important in both low\u2010density dwarf galaxies and high\u2010density gas\u2010rich galaxies.",
"doi": "10.1111/j.1365-2966.2012.20593.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2012-04-21",
"series_number": "4",
"volume": "421",
"issue": "4",
"pages": "3522-3537"
},
{
"id": "authors:213br-ryp70",
"collection": "authors",
"collection_id": "213br-ryp70",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200601-143025019",
"type": "article",
"title": "The structure of the interstellar medium of star-forming galaxies",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
}
],
"abstract": "We develop and implement numerical methods for including stellar feedback in galaxy\u2010scale numerical simulations. Our models include simplified treatments of heating by Type I and Type II supernovae, gas recycling from young stars and asymptotic giant branch winds, heating from the shocked stellar winds, H\u2003II photoionization heating and radiation pressure from stellar photons. The energetics and time dependence associated with the feedback are taken directly from stellar evolution models. We implement these stellar feedback models in smoothed particle hydrodynamic simulations with pc\u2010scale resolution, modelling galaxies from Small Magellanic Cloud (SMC) like dwarfs and Milky Way (MW) analogues to massive z\u223c 2 star\u2010forming discs. In the absence of stellar feedback, gas cools rapidly and collapses without limit into dense sub\u2010units, inconsistent with observations. By contrast, in all cases with feedback, the interstellar medium (ISM) quickly approaches a statistical steady state in which giant molecular clouds (GMCs) continuously form, disperse and re\u2010form, leading to a multiphase ISM. In this paper, we quantify the properties of the ISM and GMCs in this self\u2010regulated state. In a companion paper we study the galactic winds driven by stellar feedback. \n\nOur primary results on the structure of the ISM in star\u2010forming galaxies include the following. \n\n1. Star\u2010forming galaxies generically self\u2010regulate so that the cool, dense gas maintains Toomre's Q\u223c 1. Most of the volume is occupied by relatively diffuse hot gas, while most of the mass is in dense GMC complexes created by self\u2010gravity. The phase structure of the gas and the gas mass fraction at high densities are much more sensitive probes of the physics of stellar feedback than integrated quantities such as the Toomre Q or gas velocity dispersion. \n\n2. Different stellar feedback mechanisms act on different spatial (and density) scales. Radiation pressure and H\u2003II gas pressure are critical for preventing runaway collapse of dense gas in GMCs. Shocked supernova ejecta and stellar winds dominate the dynamics of the volume\u2010filling hot gas. However, this gas primarily vents out of the star\u2010forming disc and contributes only modestly to the mid\u2010plane ISM pressure. \n\n3. The galaxy\u2010averaged star formation rate is determined by feedback, with different mechanisms dominating in different galaxy types. For a given feedback efficiency, restricting star formation to molecular gas or modifying the cooling function has little effect on the star formation rate in the galaxies we model (including an SMC\u2010mass dwarf). By contrast, changing the feedback mechanisms or assumed feedback efficiencies directly translates to shifts off of the observed Kennicutt\u2013Schmidt relation. \n\n4. Self\u2010gravity leads to GMCs with an approximately self\u2010similar mass function \u221dM\u22122, with a high\u2010mass cut\u2010off determined by the characteristic Jeans/Toomre mass of the system. In all of our galaxy models, GMCs live for a few dynamical times before they are disrupted by stellar feedback. The net star formation efficiency in GMCs ranges from \u223c1 per cent in dwarfs and MW\u2010like spirals to nearly \u223c10 per cent in gas\u2010rich rapidly star\u2010forming galaxies. GMCs are approximately virialized, but there is a large dispersion in the virial parameter for a given GMC mass, and lower mass GMCs tend to be preferentially unbound.",
"doi": "10.1111/j.1365-2966.2012.20578.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2012-04-21",
"series_number": "4",
"volume": "421",
"issue": "4",
"pages": "3488-3521"
},
{
"id": "authors:t3y8w-36660",
"collection": "authors",
"collection_id": "t3y8w-36660",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200601-143025218",
"type": "article",
"title": "The origins of active galactic nuclei obscuration: the 'torus' as a dynamical, unstable driver of accretion",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-D"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
}
],
"abstract": "Recent multiscale simulations have made it possible to follow gas inflows responsible for high-Eddington ratio accretion on to massive black holes (BHs) from galactic scales to the BH accretion disc. When sufficient gas is driven towards a BH, gravitational instabilities generically form lopsided, eccentric discs that propagate inwards from larger radii. The lopsided stellar disc exerts a strong torque on the gas, driving inflows that fuel the growth of the BH. Here, we investigate the possibility that the same disc, in its gas-rich phase, is the putative 'torus' invoked to explain obscured active galactic nuclei (AGN) and the cosmic X-ray background. The disc is generically thick and has characteristic \u223c1\u201310\u2003pc sizes and masses resembling those required of the torus. Interestingly, the scale heights and obscured fractions of the predicted torii are substantial even in the absence of strong stellar feedback providing the vertical support. Rather, they can be maintained by strong bending modes and warps/twists excited by the inflow-generating instabilities. A number of other observed properties commonly attributed to 'feedback' processes may in fact be explained entirely by dynamical, gravitational effects: the lack of alignment between torus and host galaxy, correlations between local star formation rate (SFR) and turbulent gas velocities and the dependence of obscured fractions on AGN luminosity or SFR. We compare the predicted torus properties with observations of gas surface density profiles, kinematics, scale heights and SFR densities in AGN, and find that they are consistent in all cases. We argue that it is not possible to reproduce these observations and the observed column density distribution without a clumpy gas distribution, but allowing for simple clumping on small scales the predicted column density distribution is in good agreement with observations from\u2002NHH \u223c 10\u00b2\u2070\u201310\u00b2\u2077\u2003cm\u207b\u00b2 . We examine how the\u2002NH distribution scales with galaxy and AGN properties. The dependence is generally simple, but AGN feedback may be necessary to explain certain trends in obscured fraction with luminosity and/or redshift. In our paradigm, the torus is not merely a bystander or passive fuel source for accretion, but is itself the mechanism driving accretion. Its generic properties are not coincidence, but requirements for efficient accretion.",
"doi": "10.1111/j.1365-2966.2011.20035.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2012-02-11",
"series_number": "1",
"volume": "420",
"issue": "1",
"pages": "320-339"
},
{
"id": "authors:kb03p-1x637",
"collection": "authors",
"collection_id": "kb03p-1x637",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200601-143025313",
"type": "article",
"title": "Self-regulated star formation in galaxies via momentum input from massive stars",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
}
],
"abstract": "Feedback from massive stars is believed to play a critical role in shaping the galaxy mass function, the structure of the interstellar medium (ISM) and the low efficiency of star formation, but the exact form of the feedback is uncertain. In this paper, the first in a series, we present and test a novel numerical implementation of stellar feedback resulting from momentum imparted to the ISM by radiation, supernovae and stellar winds. We employ a realistic cooling function, and find that a large fraction of the gas cools to \u2272100 K, so that the ISM becomes highly inhomogeneous. Despite this, our simulated galaxies reach an approximate steady state, in which gas gravitationally collapses to form giant 'molecular' clouds (GMCs), dense clumps and stars; subsequently, stellar feedback disperses the GMCs, repopulating the diffuse ISM. This collapse and dispersal cycle is seen in models of Small Magellanic Cloud (SMC)-like dwarfs, the Milky Way and z\u223c 2 clumpy disc analogues. The simulated global star formation efficiencies are consistent with the observed Kennicutt\u2013Schmidt relation. Moreover, the star formation rates are nearly independent of the numerically imposed high-density star formation efficiency, density threshold and density scaling. This is a consequence of the fact that, in our simulations, star formation is regulated by stellar feedback limiting the amount of very dense gas available for forming stars. In contrast, in simulations without stellar feedback, i.e. under the action of only gravity and gravitationally induced turbulence, the ISM experiences runaway collapse to very high densities. In these simulations without feedback, the global star formation rates exceed observed galactic star formation rates by 1\u20132 orders of magnitude, demonstrating that stellar feedback is crucial to the regulation of star formation in galaxies.",
"doi": "10.1111/j.1365-2966.2011.19306.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2011-10-21",
"series_number": "2",
"volume": "417",
"issue": "2",
"pages": "950-973"
},
{
"id": "authors:cf9a6-j2s98",
"collection": "authors",
"collection_id": "cf9a6-j2s98",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200601-143025407",
"type": "article",
"title": "A physical model for the origin of the diffuse cosmic infrared background and the opacity of the Universe to very high energy \u03b3-rays",
"author": [
{
"family_name": "Younger",
"given_name": "Joshua D.",
"clpid": "Younger-J-D"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We present a physical model for origin of the cosmic diffuse infrared background (CDIRB). By utilizing the observed stellar mass function and its evolution as input to a semi-empirical model of galaxy formation, we isolate the physics driving diffuse IR emission. The model includes contributions from three primary sources of IR emission: steady-state star formation owing to isolated disc galaxies, interaction-driven bursts of star formation owing to close encounters and mergers, and obscured active galactic nuclei (AGNs). We find that most of the CDIRB is produced by equal contributions from objects at z\u223c 0.5\u20131 and z\u2273 1, as suggested by recent observations. Of those sources, the vast majority of the emission originates in systems with low to moderate IR luminosities (L_(IR) \u2272 10\u00b9\u00b2 L_\u2299); the most luminous objects contribute significant flux only at high redshifts (z \u2273 2). All star formation in ongoing mergers accounts for \u227210 per cent of the total at all wavelengths and redshifts, while emission directly attributable to the interaction-driven burst itself accounts for \u22725 per cent. We furthermore find that obscured AGNs contribute \u22721\u20132 per cent of the CDIRB at all wavelengths and redshifts, with a strong upper limit of less than 4 per cent of the total emission. Finally, since electron\u2013positron pair production interactions with the CDIRB represent the primary source of opacity to very high energy (VHE: E_\u03b3 \u2273 1 TeV) \u03b3-rays, the model provides predictions for the optical depth of the Universe to the most energetic photons. We find that these predictions agree with observations of high-energy cut-offs at \u223c TeV energies in nearby blazars, and suggest that while the Universe is extremely optically thick at \u227310 TeV, the next generation of VHE \u03b3-ray telescopes can reasonably expect detections from out to \u223c50\u2013150 Mpc.",
"doi": "10.1111/j.1365-2966.2010.17594.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2011-02-01",
"series_number": "4",
"volume": "410",
"issue": "4",
"pages": "2180-2192"
},
{
"id": "authors:7j4w5-zdz25",
"collection": "authors",
"collection_id": "7j4w5-zdz25",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200521-163330707",
"type": "article",
"title": "A physical model for z \u223c 2 dust-obscured galaxies",
"author": [
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-D"
},
{
"family_name": "Dey",
"given_name": "Arjun",
"orcid": "0000-0002-4928-4003",
"clpid": "Dey-Arjun"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Cox",
"given_name": "Thomas J.",
"clpid": "Cox-T-J"
},
{
"family_name": "Bussmann",
"given_name": "R. Shane",
"clpid": "Bussmann-R-S"
},
{
"family_name": "Brodwin",
"given_name": "Mark",
"orcid": "0000-0002-4208-798X",
"clpid": "Brodwin-M"
},
{
"family_name": "Jonsson",
"given_name": "Patrik",
"clpid": "Jonsson-P"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Groves",
"given_name": "Brent",
"orcid": "0000-0002-9768-0246",
"clpid": "Groves-B-A"
},
{
"family_name": "Younger",
"given_name": "Joshua D.",
"clpid": "Younger-J-D"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
}
],
"abstract": "We present a physical model for the origin of z\u223c 2 dust-obscured galaxies (DOGs), a class of high-redshift ultraluminous infrared galaxies (ULIRGs) selected at 24 \u03bcm which are particularly optically faint (F_(24 \u03bcm)/F)R > 1000). By combining N-body/smoothed particle hydrodynamic simulations of high-redshift galaxy evolution with 3D polychromatic dust radiative transfer models, we find that luminous DOGs (with F\u2082\u2084 \u2273 0.3 mJy at z \u223c 2) are well modelled as extreme gas-rich mergers in massive (\u223c5 \u00d7 10\u00b9\u00b2\u201310\u00b9\u00b3 M_\u2299) haloes, with elevated star formation rates (SFR; \u223c500\u20131000 M_\u2299 yr\u207b\u00b9) and/or significant active galactic nuclei (AGN) growth (\u1e40_(BH) \u2273 0.5 M_,\u2299 yr\u207b\u00b9)whereas less luminous DOGs are more diverse in nature. At final coalescence, merger-driven DOGs transition from being starburst dominated to AGN dominated, evolving from a 'bump' to a power-law (PL) shaped mid-IR (Infrared Array Camera, IRAC) spectral energy distribution (SED). After the DOG phase, the galaxy settles back to exhibiting a 'bump' SED with bluer colours and lower SFRs. While canonically PL galaxies are associated with being AGN dominated, we find that the PL mid-IR SED can owe both to direct AGN contribution and to a heavily dust obscured stellar bump at times that the galaxy is starburst dominated. Thus, PL galaxies can be either starburst or AGN dominated. Less luminous DOGs can be well-represented either by mergers or by massive (M_(baryon) \u2248 5 \u00d7 10\u00b9\u00b9 M_\u2299) secularly evolving gas-rich disc galaxies (with SFR \u2273 50 M_\u2299 yr\u207b\u00b9)). By utilizing similar models as those employed in the submillimetre galaxy (SMG) formation study of Narayanan et al., we investigate the connection between DOGs and SMGs. We find that the most heavily star-forming merger-driven DOGs can be selected as submillimetre galaxies, while both merger-driven and secularly evolving DOGs typically satisfy the BzK selection criteria. The model SEDs from the simulated galaxies match observed data reasonably well, though Mrk 231 and Arp 220 templates provide worse matches. Our models provide testable predictions of the physical masses, dust temperatures, CO linewidths and location on the M_(BH)\u2013M_(bulge) relation of DOGs. Finally, we provide public SED templates derived from these simulations.",
"doi": "10.1111/j.1365-2966.2010.16997.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2010-09",
"series_number": "3",
"volume": "407",
"issue": "3",
"pages": "1701-1720"
},
{
"id": "authors:yma64-3bq90",
"collection": "authors",
"collection_id": "yma64-3bq90",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200521-163330526",
"type": "article",
"title": "A non-parametric estimate of mass 'scoured' in galaxy cores",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
}
],
"abstract": "We present a simple estimate of the mass 'deficits' in cored spheroids, as a function of galaxy mass and radius within the galaxy. Previous attempts to measure such deficits depended on fitting some functional form to the profile at large radii extrapolating inwards; this is sensitive to the assumed functional form and does not allow for variation in nuclear profile shapes. For example, we show that literally interpreting the residuals from a single/cored Sersic function fit as implied 'deficit' can be misleading. Instead, we take advantage of larger data sets to directly construct stellar mass profiles of observed systems and measure the stellar mass enclosed in a series of physical radii (M_*(< R)), for samples of cusp and core spheroids at the same stellar mass. We show that there is a significant (model-independent) bimodality in this distribution of central structure for this sample at small radii. We non-parametrically measure the median offset between core and cusp populations (the 'deficit'\u0394M_*(< R)). We can then construct the scoured mass profile as a function of radius, without reference to any assumed functional form. The mass deficit rises in power-law fashion (\u0394M_*(< R) \u221d R^(1.3\u22121.8)) from a significant but small mass at R \u2272 10 pc, to asymptote to a maximum \u223c 0.5\u20132 M_(BH) at \u223c 100 pc, where M_(BH) is the mass of the central, supermassive black hole (BH) hosted by the spheroid. At larger radii there is no statistically significant separation between populations; the upper limit to the cumulative scoured mass at \u223ckpc is \u223c 2\u20134 M_(BH). This does not depend strongly on stellar mass. The dispersion in M_*(< R) appears larger in the core population, possibly reflecting the fact that core scouring increases the scatter in central profile shapes. We measure this broadening effect as a function of radius. The relatively low mass deficits inferred, and characteristic radii, are in good agreement with models of 'scouring' from BH binary systems.",
"doi": "10.1111/j.1365-2966.2010.16915.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2010-09",
"series_number": "1",
"volume": "407",
"issue": "1",
"pages": "447-457"
},
{
"id": "authors:9mx4f-yb880",
"collection": "authors",
"collection_id": "9mx4f-yb880",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200521-163330617",
"type": "article",
"title": "How do massive black holes get their gas?",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
}
],
"abstract": "We use multiscale smoothed particle hydrodynamic simulations to study the inflow of gas from galactic scales (\u223c10 kpc) down to \u2272 0.1 pc, at which point the gas begins to resemble a traditional, Keplerian accretion disc. The key ingredients of the simulations are gas, stars, black holes (BHs), self-gravity, star formation and stellar feedback (via a subgrid model); BH feedback is not included. We use \u223c100 simulations to survey a large parameter space of galaxy properties and subgrid models for the interstellar medium physics. We generate initial conditions for our simulations of galactic nuclei (\u2272 300 pc) using galaxy-scale simulations, including both major galaxy mergers and isolated bar-(un)stable disc galaxies. For sufficiently gas-rich, disc-dominated systems, we find that a series of gravitational instabilities generates large accretion rates of up to \u223c 1\u201310 M_\u2299 yr\u207b\u00b9 on to the BH (i.e. at \u2272 0.1 pc); this is comparable to what is needed to fuel the most luminous quasars. The BH accretion rate is highly time variable for a given set of conditions in the galaxy at \u223ckpc. At radii of >rsim 10 pc, our simulations resemble the 'bars-within-bars' model of Shlosman et al., but we show that the gas can have a diverse array of morphologies, including spirals, rings, clumps and bars; the duty cycle of these features is modest, complicating attempts to correlate BH accretion with the morphology of gas in galactic nuclei. At \u223c 1\u201310 pc, the gravitational potential becomes dominated by the BH and bar-like modes are no longer present. However, we show that the gas can become unstable to a standing, eccentric disc or a single-armed spiral mode (m = 1), in which the stars and gas precess at different rates, driving the gas to sub-pc scales (again for sufficiently gas-rich, disc-dominated systems). A proper treatment of this mode requires including star formation and the self-gravity of both the stars and gas (which has not been the case in many previous calculations). Our simulations predict a correlation between the BH accretion rate and the star formation rate at different galactic radii. We find that nuclear star formation is more tightly coupled to active galactic nucleus activity than the global star formation rate of a galaxy, but a reasonable correlation remains even for the latter.",
"doi": "10.1111/j.1365-2966.2010.17064.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2010-09",
"series_number": "3",
"volume": "407",
"issue": "3",
"pages": "1529-1564"
},
{
"id": "authors:8mbg2-dwn07",
"collection": "authors",
"collection_id": "8mbg2-dwn07",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100831-144255846",
"type": "article",
"title": "The Rise and Fall of Passive Disk Galaxies: Morphological Evolution Along the Red Sequence Revealed by COSMOS",
"author": [
{
"family_name": "Bundy",
"given_name": "Kevin",
"orcid": "0000-0001-9742-3138",
"clpid": "Bundy-K-A"
},
{
"family_name": "Scarlata",
"given_name": "Claudia",
"orcid": "0000-0002-9136-8876",
"clpid": "Scarlata-C-M"
},
{
"family_name": "Carollo",
"given_name": "C. M.",
"orcid": "0000-0003-1624-7609",
"clpid": "Carollo-C-Marcella"
},
{
"family_name": "Ellis",
"given_name": "Richard S.",
"orcid": "0000-0001-7782-7071",
"clpid": "Ellis-R-S"
},
{
"family_name": "Drory",
"given_name": "Niv",
"clpid": "Drory-N"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Salvato",
"given_name": "Mara",
"orcid": "0000-0001-7116-9303",
"clpid": "Salvato-Mara"
},
{
"family_name": "Leauthaud",
"given_name": "Alexie",
"orcid": "0000-0002-3677-3617",
"clpid": "Leauthaud-A"
},
{
"family_name": "Koekemoer",
"given_name": "Anton M.",
"orcid": "0000-0002-6610-2048",
"clpid": "Koekemoer-A-M"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
},
{
"family_name": "Ilbert",
"given_name": "Olivier",
"orcid": "0000-0002-7303-4397",
"clpid": "Ilbert-Olivier"
},
{
"family_name": "Oesch",
"given_name": "Pascal",
"orcid": "0000-0001-5851-6649",
"clpid": "Oesch-P-A"
},
{
"family_name": "Ma",
"given_name": "Chung-Pei",
"clpid": "Ma-Chung-Pei"
},
{
"family_name": "Capak",
"given_name": "Peter",
"orcid": "0000-0003-3578-6843",
"clpid": "Capak-P"
},
{
"family_name": "Pozzetti",
"given_name": "Lucia",
"clpid": "Pozzetti-L"
},
{
"family_name": "Scoville",
"given_name": "Nick",
"orcid": "0000-0002-0438-3323",
"clpid": "Scoville-N-Z"
}
],
"abstract": "The increasing abundance of passive \"red-sequence\" galaxies since z ~ 1-2 is mirrored by a coincident rise in the number of galaxies with spheroidal morphologies. In this paper, however, we show in detail, that, the correspondence between galaxy morphology and color is not perfect, providing insight into the physical origin of this evolution. Using the COSMOS survey, we study a significant population of red-sequence galaxies with disk-like morphologies. These passive disks typically have Sa-Sb morphological types with large bulges, but they are not confined to dense environments. They represent nearly one-half of all red-sequence galaxies and dominate at lower masses (\u227e10^(10) M_\u2299) where they are increasingly disk-dominated. As a function of time, the abundance of passive disks with M_* \u227e10^(11) M_\u2299 increases, but not as fast as red-sequence spheroidals in the same mass range. At higher mass, the passive disk population has declined since z ~ 1, likely because they transform into spheroidals. Based on these trends, we estimate that as much as 60% of galaxies transitioning onto the red sequence evolve through a passive disk phase. The origin of passive disks therefore has broad implications for our understanding of how star formation shuts down. Because passive disks tend to be more bulge-dominated than their star-forming counterparts, a simple fading of blue disks does not fully explain their origin. We explore the strengths and weaknesses of several more sophisticated explanations, including environmental effects, internal stabilization, and disk regrowth during gas-rich mergers. While previous work has sought to explain color and morphological transformations with a single process, these observations open the way to new insight by highlighting the fact that galaxy evolution may actually proceed through several separate stages.",
"doi": "10.1088/0004-637X/719/2/1969",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2010-08-20",
"series_number": "2",
"volume": "719",
"issue": "2",
"pages": "1969-1983"
},
{
"id": "authors:5ba28-0wn80",
"collection": "authors",
"collection_id": "5ba28-0wn80",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200521-163330430",
"type": "article",
"title": "Mergers, active galactic nuclei and 'normal' galaxies: contributions to the distribution of star formation rates and infrared luminosity functions",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Younger",
"given_name": "Joshua D.",
"clpid": "Younger-J-D"
},
{
"family_name": "Hayward",
"given_name": "Christopher C.",
"orcid": "0000-0003-4073-3236",
"clpid": "Hayward-C-C"
},
{
"family_name": "Narayanan",
"given_name": "Desika",
"orcid": "0000-0002-7064-4309",
"clpid": "Narayanan-D"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
}
],
"abstract": "We use a novel method to predict the contribution of normal star-forming galaxies, merger-induced bursts and obscured active galactic nuclei (AGN), to infrared luminosity functions (LFs) and global star formation rate (SFR) densities. We use empirical halo occupation constraints to populate haloes with galaxies and determine the distribution of normal and merging galaxies. Each system can then be associated with high-resolution hydrodynamic simulations. We predict the distribution of observed luminosities and SFRs, from different galaxy classes, as a function of redshift from z= 0 to 6. We provide fitting functions for the predicted LFs, quantify the uncertainties, and compare with observations. At all redshifts, 'normal' galaxies dominate the LF at moderate luminosities \u223cL_* (the 'knee'). Merger-induced bursts increasingly dominate at L \u226b L_*; at the most extreme luminosities, AGN are important. However, all populations increase in luminosity at higher redshifts, owing to increasing gas fractions. Thus, the 'transition luminosity' between normal and merger-dominated sources increases from the luminous infrared galaxy (LIRG)\u2013ultraluminous infrared galaxy threshold at z\u223c 0 to bright Hyper-LIRG thresholds at z\u223c 2. The transition to dominance by obscured AGN evolves similarly, at factor of several higher L_(IR). At all redshifts, non-merging systems dominate the total luminosity/SFR density, with merger-induced bursts constituting \u223c5\u201310 per cent and AGN \u223c1\u20135 per cent. Bursts contribute little to scatter in the SFR\u2013stellar mass relation. In fact, many systems identified as 'ongoing' mergers will be forming stars in their 'normal' (non-burst) mode. Counting this as 'merger-induced' star formation leads to a stronger apparent redshift evolution in the contribution of mergers to the SFR density. We quantify how the evolution in LFs depends on evolution in galaxy gas fractions, merger rates, and possible evolution in the Schmidt\u2013Kennicutt relation. We discuss areas where more detailed study, with full radiative transfer treatment of complex three-dimensional clumpy geometries in mixed AGN\u2013star-forming systems, is necessary.",
"doi": "10.1111/j.1365-2966.2009.15990.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2010-03",
"series_number": "3",
"volume": "402",
"issue": "3",
"pages": "1693-1713"
},
{
"id": "authors:5rb58-b6f63",
"collection": "authors",
"collection_id": "5rb58-b6f63",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200521-163330318",
"type": "article",
"title": "A new empirical method to infer the starburst history of the Universe from local galaxy properties",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
}
],
"abstract": "The centres of ellipticals and bulges are formed dissipationally, via gas inflows over short time-scales \u2013 the 'starburst' mode of star formation. Recent work has shown that the surface brightness profiles, kinematics and stellar populations of spheroids can be used to separate the dissipational component from the dissipationless 'envelope' made up of stars formed over more extended histories in separate objects, and violently assembled in mergers. Given high-resolution, detailed observations of these 'burst relic' components of ellipticals (specifically their stellar mass surface density profiles), together with the simple assumptions that some form of the Kennicutt\u2013Schmidt law holds and that the burst was indeed a dissipational, gas-rich event, we show that it is possible to invert the observed profiles and obtain the time- and space-dependent star formation history of each burst. We perform this exercise using a large sample of well-studied spheroids, which have also been used to calibrate estimates of the 'burst relic' populations. We show that the implied bursts scale in magnitude, mass and peak star formation rate (SFR) with galaxy mass in a simple manner, and provide fits for these correlations. The typical burst mass M_(burst) is \u223c 10 per cent of the total spheroid mass, the characteristic starburst time-scale implied is a nearly galaxy-mass-independent t_(burst) \u223c 10\u2078 yr, the peak SFR of the burst is \u223cM_(burst)/t_(burst) and bursts decay subsequently in power-law fashion as \u1e40_\u2605 \u221d t^(-2.4). As a function of time, we obtain the spatial size of the starburst; burst sizes at peak activity scale with burst mass in a manner similar to the observed spheroid size\u2013mass relation, but are smaller than the full galaxy size by a factor of \u223c10; the size grows in time as the central, most dense regions are more quickly depleted by star formation as R_(burst) \u221d t^(0.5). Combined with observational measurements of the nuclear stellar population ages of these systems \u2013 i.e. the distribution of times when these bursts occurred \u2013 it is possible to re-construct the dissipational burst contribution to the distribution of SFRs and infrared (IR) luminosity functions (LFs) and luminosity density of the Universe. We do so and show that these burst LFs agree well with the observed IR LFs at the brightest luminosities, at redshifts z\u223c 0\u20132. At low luminosities, however, bursts are always unimportant; the transition luminosity between these regimes increases with redshift from the ultraluminous infrared galaxy threshold at z\u223c 0 to hyper-luminous infrared galaxy thresholds at z\u223c 2. At the highest redshifts z\u2273 2, we can set strict upper limits on starburst magnitudes, based on the maximum stellar mass remaining at high densities at z= 0, and find tension between these and estimated number counts of sub-millimetre galaxies, implying that some change in bolometric corrections, the number counts themselves or the stellar initial mass function may be necessary. At all redshifts, bursts are a small fraction of the total SFR or luminosity density, \u223c5\u201310 per cent, in good agreement with estimates of the contribution of merger-induced star formation.",
"doi": "10.1111/j.1365-2966.2009.15933.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2010-02",
"series_number": "2",
"volume": "402",
"issue": "2",
"pages": "985-1004"
},
{
"id": "authors:qxrkq-gfr67",
"collection": "authors",
"collection_id": "qxrkq-gfr67",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200521-163330054",
"type": "article",
"title": "Quasar feedback: more bang for your buck",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Elvis",
"given_name": "Martin",
"clpid": "Elvis-M"
}
],
"abstract": "We propose a 'two-stage' model for the effects of feedback from a bright quasar on the cold gas in a galaxy. It is difficult for winds or other forms of feedback from near the accretion disc to directly impact (let alone blow out of the galaxy) dense molecular clouds at \u223ckpc. However, if such feedback can drive a weak wind or outflow in the hot, diffuse interstellar medium (a relatively 'easy' task), then in the wake of such an outflow passing over a cold cloud, a combination of instabilities and simple pressure gradients will drive the cloud material to effectively expand in the direction perpendicular to the incident outflow. This shredding/expansion (and the corresponding decrease in density) may alone be enough to substantially suppress star formation in the host. Moreover, such expansion, by even a relatively small factor, dramatically increases the effective cross-section of the cloud material and makes it much more susceptible to both ionization and momentum coupling from absorption of the incident quasar radiation field. We show that even a moderate effect of this nature can dramatically alter the ability of clouds at large radii to be fully ionized and driven into a secondary outflow by radiation pressure. Since the amount of momentum and volume which can be ionized by observed quasar radiation field is more than sufficient to affect the entire cold gas supply once it has been altered in this manner (and the 'initial' feedback need only initiate a moderate wind in the low-density hot gas), this reduces by an order of magnitude the required energy budget for feedback to affect a host galaxy. Instead of \u223c5 per cent of the radiated energy (\u223c100 per cent momentum) needed if the initial feedback must directly heat or 'blow out' the galactic gas, if only \u223c0.5 per cent of the luminosity (\u223c10 per cent momentum) can couple to drive the initial hot outflow, this mechanism could be efficient. This amounts to hot gas outflow rates from near the accretion disc of only \u223c5\u201310 per cent of the black hole accretion rate.",
"doi": "10.1111/j.1365-2966.2009.15643.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2010-01",
"series_number": "1",
"volume": "401",
"issue": "1",
"pages": "7-14"
},
{
"id": "authors:rkb15-1fq81",
"collection": "authors",
"collection_id": "rkb15-1fq81",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200521-163330227",
"type": "article",
"title": "When should we treat galaxies as isolated?",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Ma",
"given_name": "Chung-Pei",
"clpid": "Ma-Chung-Pei"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
}
],
"abstract": "Traditionally, secular evolution is defined as evolution of systems where the internal growth of structure and instabilities dominates the growth via external drivers (e.g. accretion and mergers). Most study has focused on 'isolated' galaxies, where seed asymmetries may represent realistic cosmological substructure, but subsequent evolution ignores galaxy growth and interactions. Large-scale modes in the disc then grow on a time-scale of the order of a disc rotation period (\u223c0.1\u20131\u2003Gyr). If, however, galaxies evolve cosmologically on a shorter time-scale, then it may not be appropriate to consider them 'isolated'. We outline simple scalings to ask whether, under realistic conditions, the time-scale for secular evolution is shorter than the time-scale for cosmological accretion and mergers. We show that this is the case in a relatively narrow but important range of perturbation amplitudes corresponding to substructure or mode/bar fractional amplitudes \u03b4 \u223c 0.01\u20130.1, the range of most interest for observed strong bars and most pseudo-bulges. At smaller amplitudes \u03b4 \u226a 0.1, systems are not isolated: typical discs will grow by accretion at a comparable level over even a single dynamical time. At larger amplitudes \u03b4\u226b 0.1, the evolution is no longer secular; the direct gravitational evolution of the seed substructure swamps the internal disc response. We derive criteria for when discs can be well approximated as 'isolated' as a function of mass, redshift and disc stability. The relevant parameter space shrinks at higher mass, higher disc stability and higher z as accretion rates increase. The cosmological rate of galaxy evolution also defines a maximum bar/mode lifetime of practical interest, of \u223c0.1\u2003t_(Hubble)(z). Longer lived modes will encounter cosmological effects and will decouple from their drivers (if they are driven).",
"doi": "10.1111/j.1365-2966.2009.15700.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2010-01",
"series_number": "2",
"volume": "401",
"issue": "2",
"pages": "1131-1140"
},
{
"id": "authors:xteht-cbj04",
"collection": "authors",
"collection_id": "xteht-cbj04",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200521-163330136",
"type": "article",
"title": "Discriminating between the physical processes that drive spheroid size evolution",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Bundy",
"given_name": "Kevin",
"orcid": "0000-0001-9742-3138",
"clpid": "Bundy-K-A"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
},
{
"family_name": "Wuyts",
"given_name": "Stijn",
"clpid": "Wuyts-S"
},
{
"family_name": "Cox",
"given_name": "Thomas J.",
"clpid": "Cox-T-J"
}
],
"abstract": "Observations have shown that massive galaxies at high redshift have much smaller effective radii than galaxies of similar mass today; however, recent work has shown that they have similar central densities. The primary growth of size, therefore, relates to the apparent relative abundance of low-density material at low redshifts. But various models have been proposed to accomplish this, and the exact contribution of these mechanisms, relative to others that would, for example, lower the density of the system uniformly, or relate to possible observational misestimates of the stellar mass distribution, remain uncertain, as does the degree to which this evolution is driven by processes of initial spheroid formation versus subsequent 'dry' assembly of spheroids. These different possibilities also yield dramatically different constraints on any possible evolution in the M_(BH)\u2013\u03c3 relation. Here, we compile observations of spheroid properties as a function of redshift and use them to test the different proposed models, each of which we have calibrated and studied in a suite of high-resolution hydrodynamic simulations. We show that the evolution in progenitor disc gas fractions with redshift gives rise to the initial formation of smaller spheroids at high redshift. We then consider how these early-forming systems must evolve to be consistent with the larger sizes of old spheroids today. We consider (1) equal-density 'dry' mergers, (2) later major or minor 'dry' mergers with less dense galaxies, (3) adiabatic expansion, after significant gas mass loss, (4) gradients in stellar mass-to-light ratios from young nuclear stellar populations (yielding smaller R_e at early times, which vanish as the system fades), (5) biases in the stellar mass estimation of high-redshift (young) systems (from e.g. uncertain asymptotic giant branch starlight contributions) and (6) observational effects (possible biases in fitting or missed light from surface brightness dimming, or the effects of different definitions of effective radii). In principle, any of these models could be tuned to explain any observed effective radius evolution. However, the predicted evolution in velocity dispersions, central stellar mass surface densities and profile shape are very distinct. Comparing with observations, only model (2), later or minor 'dry' mergers with less dense systems, is consistent with the constraints as an explanation of the entire effect. Moreover, it is the only model which allows for any evolution in M_(BH)\u2013\u03c3 towards more massive black holes (BHs) at high redshift. Still, the amount of merging needed for this to explain the observed factor of \u223c6 size evolution is larger than that predicted by hierarchical growth and clustering constraints. We, therefore, consider a cosmologically motivated model with high-resolution simulations, in which the initial galaxy forms in a gas rich merger and is observed at an appropriate age under representative conditions, then evolves undergoing a 'typical' level of dry merging and mass loss. We show that this case is consistent with all the observational constraints without tension with cosmological expectations. Effect (2), which builds up an extended, low-density envelope, dominates the evolution (giving factors \u223c2\u20133 size evolution), but effects (1), (3), (4) and (possibly) (6) each contribute an additional \u223c20 per cent size evolution (net factor of \u223c2), together bringing the natural cosmological predictions into good agreement with the combination of observational constraints. We discuss implications for the evolution in correlations between BH and host bulge properties and show that this naturally predicts some evolution similar to that observed; better observations of BH masses could also constrain host galaxy merger histories.",
"doi": "10.1111/j.1365-2966.2009.15699.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2010-01",
"series_number": "2",
"volume": "401",
"issue": "2",
"pages": "1099-1117"
},
{
"id": "authors:xa1q1-dc818",
"collection": "authors",
"collection_id": "xa1q1-dc818",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200601-143025513",
"type": "article",
"title": "Metallicity gradients at large galactocentric radii using the near-infrared Calcium triplet",
"author": [
{
"family_name": "Foster",
"given_name": "Caroline",
"orcid": "0000-0003-0247-1204",
"clpid": "Foster-C"
},
{
"family_name": "Proctor",
"given_name": "Robert N.",
"clpid": "Proctor-R-N"
},
{
"family_name": "Forbes",
"given_name": "Duncan A.",
"clpid": "Forbes-D-A"
},
{
"family_name": "Spolaor",
"given_name": "Max",
"clpid": "Spolaor-Max"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Brodie",
"given_name": "Jean P.",
"orcid": "0000-0002-9658-8763",
"clpid": "Brodie-J-P"
}
],
"abstract": "We describe a new spectroscopic technique for measuring radial metallicity gradients out to large galactocentric radii. We use the DEep Imaging Multi-Object Spectrograph (DEIMOS) on the Keck telescope and the galaxy spectrum extraction technique of Proctor et al. We also make use of the metallicity sensitive near-infrared Calcium II triplet (CaT) features together with single stellar population models to obtain metallicities. Our technique is applied as a pilot study to a sample of three relatively nearby (\u226430 Mpc) intermediate-mass to massive early-type galaxies. Results are compared with previous literature inner region values and generally show good agreement. We also include a comparison with profiles from dissipational disc\u2013disc major merger simulations. Based on our new extended metallicity gradients combined with other observational evidence and theoretical predictions, we discuss possible formation scenarios for the galaxies in our sample. The limitations of our new technique are also discussed.",
"doi": "10.1111/j.1365-2966.2009.15606.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2009-12-21",
"series_number": "4",
"volume": "400",
"issue": "4",
"pages": "2135-2146"
},
{
"id": "authors:pd64x-btz91",
"collection": "authors",
"collection_id": "pd64x-btz91",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200529-093431825",
"type": "article",
"title": "The small scatter in BH-host correlations and the case for self-regulated BH growth",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
},
{
"family_name": "Thompson",
"given_name": "Todd A.",
"clpid": "Thompson-T-A"
}
],
"abstract": "Supermassive black holes (BHs) obey tight scaling relations between their mass and host galaxy properties such as total stellar mass, velocity dispersion and potential well depth. This has led to the development of self-regulated models for BH growth, in which feedback from the central BH halts its own growth upon reaching a critical threshold. However, models have also been proposed in which feedback plays no role: so long as a fixed fraction of the host gas supply is accreted, relations like those observed can be reproduced. Here, we argue that the scatter in the observed BH\u2013host correlations presents a demanding constraint on any model for these correlations, and that it favours self-regulated models of BH growth. We show that the scatter in the stellar mass fraction within a radius R in observed ellipticals and spheroids increases strongly at small R. At a fixed total stellar mass (or host velocity dispersion), on very small scales near the BH radius of influence, there is an order-of-magnitude scatter in the amount of gas that must have entered and formed stars. In short, the BH appears to 'know more' about the global host galaxy potential on large scales than the stars and gas supply on small scales. This is predicted in self-regulated models; however, models where there is no feedback would generically predict order-of-magnitude scatter in the BH\u2013host correlations. Likewise, models in which the BH feedback in the 'bright' mode does not regulate the growth of the BH itself, but sets the stellar mass of the galaxy by inducing star formation or blowing out a mass in gas much larger than the galaxy stellar mass, are difficult to reconcile with the scatter on small scales.",
"doi": "10.1111/j.1365-2966.2009.15132.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2009-09-01",
"series_number": "1",
"volume": "398",
"issue": "1",
"pages": "303-311"
},
{
"id": "authors:pr61c-7cj72",
"collection": "authors",
"collection_id": "pr61c-7cj72",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200521-163329824",
"type": "article",
"title": "Are most low-luminosity active galactic nuclei really obscured?",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Hickox",
"given_name": "Ryan",
"orcid": "0000-0003-1468-9526",
"clpid": "Hickox-R-C"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
}
],
"abstract": "At low Eddington ratios (\u1e41), two effects make it more difficult to detect certain active galactic nuclei (AGN) given a particular set of selection methods. First, even allowing for fixed accretion physics, at low \u1e41 AGN become less luminous relative to their hosts, diluting their emission; the magnitude of the dilution depends on host properties and, therefore, on luminosity and redshift. Secondly, low-forumla systems are expected and observed to transition to a radiatively inefficient state, which changes the spectral energy distribution (SED) shape and dramatically decreases the luminosity at optical through infrared (IR) wavelengths. The effects of dilution are unavoidable, while the precise changes in accretion physics at low \u1e41 are somewhat uncertain, but potentially very important for our understanding of AGN. These effects will have different implications for samples with different selection criteria, and generically lead to differences in the AGN populations recovered in observed samples, even at fixed bolometric luminosity and after correction for obscuration. Although the true Eddington ratio distribution may depend strongly on mass/luminosity, this will be seen only in surveys robust to dilution and radiative inefficiency, such as X-ray or narrow-line samples; by contrast, selection effects imply that AGN in optical samples will have uniformly high Eddington ratios, with little dependence on luminosity, even at low L_(bol) where the median 'true' \u1e41 \u2272 0.01. These same selection effects also imply that different selection criteria pick out systems with different hosts: as a result, the clustering of low-luminosity optical/IR sources will be weaker than that of X-ray sources, and optical/IR Seyferts will reside in more disc-dominated galaxies, while X-ray-selected Seyferts will be preferentially in early-type systems. Taken together, these effects can naturally explain longstanding, apparently contradictory claims in the literature regarding AGN Eddington ratio distributions, host populations and clustering. Finally, we show that if current observed Eddington ratio distributions are correct, a large fraction of low-luminosity AGN currently classified as 'obscured' are in fact radiatively diluted and/or radiatively inefficient, not obscured by gas or dust. This is equally true if X-ray hardness is used as a proxy for obscuration, since radiatively inefficient SEDs near \u1e41 ~ 0.01 are characteristically X-ray hard. These effects can explain most of the claimed luminosity/redshift dependence in the 'obscured' AGN population, with the true obscured fraction as low as \u223c20 per cent.",
"doi": "10.1111/j.1365-2966.2009.15136.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2009-09",
"series_number": "1",
"volume": "398",
"issue": "1",
"pages": "333-349"
},
{
"id": "authors:mf513-d4k04",
"collection": "authors",
"collection_id": "mf513-d4k04",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200521-163329967",
"type": "article",
"title": "Compact high-redshift galaxies are the cores of the most massive present-day spheroids",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Bundy",
"given_name": "Kevin",
"orcid": "0000-0001-9742-3138",
"clpid": "Bundy-K-A"
},
{
"family_name": "Murray",
"given_name": "Norman",
"clpid": "Murray-N-W"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-E"
},
{
"family_name": "Lauer",
"given_name": "Tod R.",
"clpid": "Lauer-T-R"
},
{
"family_name": "Ma",
"given_name": "Chung-Pei",
"clpid": "Ma-Chung-Pei"
}
],
"abstract": "Observations suggest that the effective radii of high-redshift massive spheroids are as much as a factor of \u223c6 smaller than low-redshift galaxies of comparable mass. Given the apparent absence of low-redshift counterparts, this has often been interpreted as indicating that the high-density, compact red galaxies must be 'puffed up' by some mechanism. We compare the ensemble of high-redshift observations with large samples of well-observed, low-redshift ellipticals. At the same physical radii, the stellar surface mass densities of low- and high-redshift systems are comparable. Moreover, the abundance of high surface density material at low redshift is comparable to or larger than that observed at z > 1\u20132, consistent with the continuous buildup of spheroids over this time. The entire population of compact, high-redshift red galaxies may be the progenitors of the high-density cores of present-day ellipticals, with no need for a decrease in stellar density from z= 2 to 0. The primary difference between low- and high-redshift systems is thus the observed low-density material at large radii in low-redshift spheroids (rather than the high-density material in high-redshift spheroids). Such low-density material may either (1) assemble at z < 2 or (2) be present, but not yet detected, at z > 2. Mock observations of low-redshift massive systems suggest that the amount of low-density material at high redshifts is indeed significantly less than that at z= 0. However, deeper observations will be important in constraining the exact amount (or lack thereof) and distribution of this material, and how it builds up with redshift. We show that, without deep observations, the full extent of such material even at low redshifts can be difficult to determine, in particular if the mass profile is not exactly a single Sersic profile. We discuss the implications of our results for physical models of galaxy evolution.",
"doi": "10.1111/j.1365-2966.2009.15062.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2009-09",
"series_number": "2",
"volume": "398",
"issue": "2",
"pages": "898-910"
},
{
"id": "authors:tz9vj-k3687",
"collection": "authors",
"collection_id": "tz9vj-k3687",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200529-093432060",
"type": "article",
"title": "The effects of gas on morphological transformation in mergers: implications for bulge and disc demographics",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Somerville",
"given_name": "Rachel S.",
"clpid": "Somerville-R-S"
},
{
"family_name": "Cox",
"given_name": "Thomas J.",
"clpid": "Cox-T-J"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
},
{
"family_name": "Jogee",
"given_name": "Shardha",
"clpid": "Jogee-Shardha"
},
{
"family_name": "Kere\u0161",
"given_name": "Du\u0161an",
"orcid": "0000-0002-1666-7067",
"clpid": "Kere\u0161-D"
},
{
"family_name": "Ma",
"given_name": "Chung-Pei",
"clpid": "Ma-Chung-Pei"
},
{
"family_name": "Robertson",
"given_name": "Brant",
"orcid": "0000-0002-4271-0364",
"clpid": "Robertson-B-E"
},
{
"family_name": "Stewart",
"given_name": "Kyle",
"clpid": "Stewart-K-R"
}
],
"abstract": "Transformation of discs into spheroids via mergers is a well-accepted element of galaxy formation models. However, recent simulations have shown that the bulge formation is suppressed in increasingly gas-rich mergers. We investigate the global implications of these results in a cosmological framework, using independent approaches: empirical halo-occupation models (where galaxies are populated in haloes according to observations) and semi-analytic models. In both, ignoring the effects of gas in mergers leads to the overproduction of spheroids: low- and intermediate-mass galaxies are predicted to be bulge-dominated (B/T\u223c 0.5 at <10\u00b9\u2070 M_\u2299, with almost no 'bulgeless' systems), even if they have avoided major mergers. Including the different physical behaviour of gas in mergers immediately leads to a dramatic change: bulge formation is suppressed in low-mass galaxies, observed to be gas-rich (giving B/T\u223c 0.1 at <10\u00b9\u2070 M_\u2299, with a number of bulgeless galaxies in good agreement with observations). Simulations and analytic models which neglect the similarity-breaking behaviour of gas have difficulty reproducing the strong observed morphology\u2013mass relation. However, the observed dependence of gas fractions on mass, combined with suppression of bulge formation in gas-rich mergers, naturally leads to the observed trends. Discrepancies between observations and models that ignore the role of gas increase with redshift; in models that treat gas properly, galaxies are predicted to be less bulge-dominated at high redshifts, in agreement with the observations. We discuss implications for the global bulge mass density and future observational tests.",
"doi": "10.1111/j.1365-2966.2009.14983.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2009-08-01",
"series_number": "2",
"volume": "397",
"issue": "2",
"pages": "802-814"
},
{
"id": "authors:wv289-brp80",
"collection": "authors",
"collection_id": "wv289-brp80",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200529-093432282",
"type": "article",
"title": "A semi-analytic model for the co-evolution of galaxies, black holes and active galactic nuclei",
"author": [
{
"family_name": "Somerville",
"given_name": "Rachel S.",
"clpid": "Somerville-R-S"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Cox",
"given_name": "Thomas J.",
"clpid": "Cox-T-J"
},
{
"family_name": "Robertson",
"given_name": "Brant E.",
"orcid": "0000-0002-4271-0364",
"clpid": "Robertson-B-E"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
}
],
"abstract": "We present a new semi-analytic model that self-consistently traces the growth of supermassive black holes (BH) and their host galaxies within the context of the Lambda cold dark matter (\u039bCDM) cosmological framework. In our model, the energy emitted by accreting black holes regulates the growth of the black holes themselves, drives galactic scale winds that can remove cold gas from galaxies, and produces powerful jets that heat the hot gas atmospheres surrounding groups and clusters. We present a comprehensive comparison of our model predictions with observational measurements of key physical properties of low-redshift galaxies, such as cold gas fractions, stellar metallicities and ages, and specific star formation rates. We find that our new models successfully reproduce the exponential cut-off in the stellar mass function and the stellar and cold gas mass densities at z\u223c 0, and predict that star formation should be largely, but not entirely, quenched in massive galaxies at the present day. We also find that our model of self-regulated BH growth naturally reproduces the observed relation between BH mass and bulge mass. We explore the global formation history of galaxies and black holes in our models, presenting predictions for the cosmic histories of star formation, stellar mass assembly, cold gas and metals. We find that models assuming the 'concordance'\u039bCDM cosmology overproduce star formation and stellar mass at high redshift (z\u2273 2). A model with less small-scale power predicts less star formation at high redshift, and excellent agreement with the observed stellar mass assembly history, but may have difficulty accounting for the cold gas in quasar absorption systems at high redshift (z\u223c 3\u20134).",
"doi": "10.1111/j.1365-2966.2008.13805.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2008-12-01",
"series_number": "2",
"volume": "391",
"issue": "2",
"pages": "481-506"
},
{
"id": "authors:nzp7f-g3k63",
"collection": "authors",
"collection_id": "nzp7f-g3k63",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200529-093432189",
"type": "article",
"title": "Is the dependence of spectral index on luminosity real in optically selected AGN samples?",
"author": [
{
"family_name": "Tang",
"given_name": "Su Min",
"clpid": "Tang-Su-Min"
},
{
"family_name": "Zhang",
"given_name": "Shuang Nan",
"clpid": "Zhang-Shuang-Nan"
},
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
}
],
"abstract": "We critically examine the dependence of spectral index on luminosity in optically selected AGN samples. An analysis of optically selected high-z quasars showed an anticorrelation of \u03b1_(OX), the spectral index between the rest-frame 2500 \u00c5 and 2 keV, with optical luminosity. We examine this relationship by means of Monte Carlo simulations and conclude that a constant \u03b1OX independent of optical luminosity is still consistent with this high-z sample. We further find that contributions of large dispersions and narrow range of optical luminosity are most important for the apparent, yet artificial, \u03b1_(OX)\u2013l)o correlation reported. We also examine another, but more complete, low-z optical selected AGN sub-sample from Steffen et al., and our analysis shows that a constant \u03b1OX independent of optical luminosity is also consistent with the data. By comparing X-ray and optical luminosity functions, we find that a luminosity-independent \u03b1_(OX) is in fact more preferred than the luminosity-dependent \u03b1_(OX) model. We also discuss the selection effects caused by flux limits, which might systematically bias the l_X\u2013l_o relation and cause discrepancy in optically selected and X-ray selected AGN samples. To correctly establish a dependence of \u03b1_(OX) of AGNs on their luminosity, a larger and more complete sample is needed and consequences of luminosity dispersions and selection effects in flux-limited samples must be taken into account properly.",
"doi": "10.1111/j.1365-2966.2007.11589.x",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2007-05-21",
"series_number": "3",
"volume": "377",
"issue": "3",
"pages": "1113-1121"
},
{
"id": "authors:vq9a0-ha207",
"collection": "authors",
"collection_id": "vq9a0-ha207",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20091112-122300293",
"type": "article",
"title": "Observational Evidence for the Coevolution of Galaxy Mergers, Quasars, and the Blue/Red Galaxy Transition",
"author": [
{
"family_name": "Hopkins",
"given_name": "Philip F.",
"orcid": "0000-0003-3729-1684",
"clpid": "Hopkins-P-F"
},
{
"family_name": "Bundy",
"given_name": "Kevin",
"orcid": "0000-0001-9742-3138",
"clpid": "Bundy-K-A"
},
{
"family_name": "Hernquist",
"given_name": "Lars",
"orcid": "0000-0001-6950-1629",
"clpid": "Hernquist-L"
},
{
"family_name": "Ellis",
"given_name": "Richard S.",
"orcid": "0000-0001-7782-7071",
"clpid": "Ellis-R-S"
}
],
"abstract": "We compile a number of observations to estimate the time-averaged rate of formation or buildup of red sequence galaxies, as a function of mass and redshift. Comparing this with the mass functions of mergers and quasar hosts, and independently comparing their clustering properties as a function of redshift, we find that these populations trace the same mass distribution, with similar evolution, at redshifts 0 < z \u227e 1.5. Knowing one of the quasar, merger, or elliptical mass/luminosity functions, it is possible to predict the others. Allowing for greater model dependence, we compare the rate of early-type buildup with the implied merger and quasar triggering rates as a function of mass and redshift and find agreement. Over this redshift range, observed merger fractions can account for the entire bright quasar luminosity function and buildup of the red sequence at all but the highest masses at low redshift (\u2273 10^(11) M_\u2299 at z \u227e 0.3) where \"dry\" mergers appear to dominate. This supports a necessary prediction of theories where mergers between gas-rich galaxies produce ellipticals with an associated phase of quasar activity, after which the remnant becomes red. These populations trace a similar characteristic transition mass, possibly reflecting the mass above which the elliptical population is mostly (\u227350%) assembled at a given redshift, which increases with redshift over the observed range in a manner consistent with suggestions that cosmic downsizing may apply to red galaxy assembly as well as star formation. These mass distributions as a function of redshift do not uniformly trace the all/red/blue galaxy population, ruling out models in which quasar activity is generically associated with star formation or is long lived in \"old\" systems.",
"doi": "10.1086/512091",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2007-04-20",
"series_number": "2",
"volume": "659",
"issue": "2",
"pages": "976-996"
}
]