[ { "id": "authors:chj5f-4s956", "collection": "authors", "collection_id": "chj5f-4s956", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-222001546", "type": "monograph", "title": "Effects of the environment on the multiplicity properties 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": "Raju", "given_name": "Aman N.", "clpid": "Raju-Aman-N" }, { "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": "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": "Most observed stars are part of a multiple star system, but the formation of such systems and the role of environment and various physical processes is still poorly understood. We present a suite of radiation-magnetohydrodynamic simulations of star-forming molecular clouds from the STARFORGE project that include stellar feedback with varied initial surface density, magnetic fields, level of turbulence, metallicity, interstellar radiation field, simulation geometry and turbulent driving. In our fiducial cloud the raw simulation data reproduces the observed multiplicity fractions for Solar-type and higher mass stars, similar to previous works. However, after correcting for observational incompleteness the simulation under-predicts these values. The discrepancy is likely due to the lack of disk fragmentation, as the simulation only resolves multiples that form either through capture or core fragmentation. The raw mass distribution of companions is consistent with randomly drawing from the initial mass function for the companions of > 1 M_\u2299 stars, however, accounting for observational incompleteness produces a flatter distribution similar to observations. We show that stellar multiplicity changes as the cloud evolves and anti-correlates with stellar density. This relationship also explains most multiplicity variations between runs, i.e., variations in the initial conditions that increase stellar density (increased surface density, reduced turbulence) decrease multiplicity. While other parameters, such as metallicity, interstellar radiation, and geometry significantly affect the star formation history or the IMF, varying them produces no clear trend in stellar multiplicity properties.", "doi": "10.48550/arXiv.2208.02844", "publisher": "arXiv", "publication_date": "2022-08-04" }, { "id": "authors:zgxyd-vqr09", "collection": "authors", "collection_id": "zgxyd-vqr09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-192431512", "type": "monograph", "title": "Disruption of Dark Matter Minihaloes 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": "Many theories of dark matter beyond the Weakly Interacting Massive Particles (WIMP) paradigm feature an enhanced matter power spectrum on sub-parsec scales, leading to the formation of dense dark matter minihaloes. While these minihaloes are currently weakly constrained, future local observations, through a variety of techniques, may strongly constrain such substructures. The survival probability of those dense minihaloes in the Milky Way environment is crucial for interpreting local observations. In this work, we investigate two disruption effects: stellar disruption and (smooth) tidal disruption. These two mechanisms are studied using semi-analytic 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, and apply the model to the realistic Milky Way disk environment. For tidal disruption, we also perform N-body simulations to confirm the effectiveness of the analytic treatment. Finally, we propose a framework to combine the stellar and tidal disruption of minihaloes with an orbit model, using it to make predictions for the overall survival probability of minihaloes in the Milky Way. We find the survival fraction for dense dark matter minihaloes, e.g. for axion miniclusters and minihaloes from Early Matter Domination, is \u223c70%, with the relatively low-mass, compact population surviving. The survival fraction is insensitive to the detailed model parameters. We discuss various implications for their mass functions and future detection prospects.", "doi": "10.48550/arXiv.2207.11276", "publisher": "arXiv", "publication_date": "2022-07-22" }, { "id": "authors:mxhms-8zd03", "collection": "authors", "collection_id": "mxhms-8zd03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-222004923", "type": "monograph", "title": "Gusts in the Headwind: Uncertainties in Direct Dark Matter Detection", "author": [ { "family_name": "Lawrence", "given_name": "Grace E.", "clpid": "Lawrence-Grace-E" }, { "family_name": "Duffy", "given_name": "Alan R.", "clpid": "Duffy-Alan-R" }, { "family_name": "Blake", "given_name": "Chris A.", "clpid": "Blake-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 backreaction, 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 which 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.", "publisher": "arXiv", "publication_date": "2022-07-15" }, { "id": "authors:mbyk8-smq11", "collection": "authors", "collection_id": "mbyk8-smq11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-222008305", "type": "monograph", "title": "Realistic HI scale heights of Milky Way-mass galaxies in the FIREbox cosmological volume", "author": [ { "family_name": "Gensior", "given_name": "Jindra", "orcid": "0000-0001-6119-9883", "clpid": "Gensior-Jindra" }, { "family_name": "Feldmann", "given_name": "Robert", "orcid": "0000-0002-1109-1919", "clpid": "Feldmann-Robert" }, { "family_name": "Mayer", "given_name": "Lucio", "clpid": "Mayer-Lucio" }, { "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" } ], "abstract": "Accurately reproducing the thin cold gas discs observed in nearby spiral galaxies has been a long standing issue in cosmological simulations. Here, we present measurements of the radially resolved HI scale height in 22 non-interacting Milky Way-mass galaxies from the FIREbox cosmological volume. We measure the HI scale heights using five different approaches commonly used in the literature: fitting the vertical volume density distribution with a Gaussian, the distance between maximum and half-maximum of the vertical volume density distribution, a semi-empirical description using the velocity dispersion and the galactic gravitational potential, the analytic assumption of hydrostatic equilibrium, and the distance from the midplane which encloses \u227360 per cent of the HI mass. We find median HI scale heights, measured using the vertical volume distribution, that range from ~100 pc in the galactic centres to ~800 pc in the outskirts and are in excellent agreement with recent observational results. We speculate that the presence of a realistic multiphase interstellar medium, including cold gas, and realistic stellar feedback are the drivers behind the realistic HI scale heights.", "doi": "10.48550/arXiv.2207.03493", "publisher": "arXiv", "publication_date": "2022-07-07" }, { "id": "authors:fdfv1-qbm39", "collection": "authors", "collection_id": "fdfv1-qbm39", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-222011684", "type": "monograph", "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", "clpid": "Du-Xiaolong" }, { "family_name": "Yang", "given_name": "Shengqi", "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 simple semi-analytic procedure for computing the density profile of self-interacting dark-matter (SIDM) haloes with the gravitational influence from the inhabitant galaxies. We show that the model agrees well with cosmological SIDM simulations over the entire core-forming stage and 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 link in the context of the structural diversity of bright dwarf galaxies. The fast speed of the method facilitates analyses that would be challenging for numerical simulations -- notably, 1) 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\u1d65\u1d62\u1d63, and galaxy compactness, r_(1/2)/R\u1d65\u1d62\u1d63; 2) we show with high statistical precision that for typical Milky-Way-like systems, the SIDM profiles are similar to their CDM counterparts; and 3) we delineate the regime of gravothermal core-collapse in the M_b/M\u1d65\u1d62\u1d63 - r_(1/2)/R\u1d65\u1d62\u1d63 space, for a given cross section and a given halo 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 future improvements of the fluid model. We have made our programs for the model publicly available at https://github.com/JiangFangzhou/SIDM.", "doi": "10.48550/arXiv.2206.12425", "publisher": "arXiv", "publication_date": "2022-06-24" }, { "id": "authors:y1dkc-0h420", "collection": "authors", "collection_id": "y1dkc-0h420", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220818-003825154", "type": "monograph", "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-Christopher-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 idealised 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 Myr after coalescence using kinematic asymmetry with 66% completeness, depending upon merger phase and the field-of-view of the observation. We detect fewer mergers in the pair phase (40%) and many more in the merging and post-coalescence phases (97%). 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% overall, 79% in pairs, and close to 100% 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": "10.48550/arXiv.2206.07545", "publisher": "arXiv", "publication_date": "2022-06-15" }, { "id": "authors:5819m-6xa04", "collection": "authors", "collection_id": "5819m-6xa04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-222015071", "type": "monograph", "title": "Dissipative Dark Matter on FIRE: II. Observational signatures and constraints from local 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 analyze the first set of 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 modelled as a constant fractional energy dissipation (f_(diss) = 0.5). In this paper, we examine the properties of dwarf galaxies with M\u2217 \u223c 10\u2075-10\u2079 M_\u2299 in both isolation and within Milky Way-mass hosts. For isolated dwarfs, we find more compact galaxy sizes and promotion of stellar/neutral gas disk formation in dSIDM with (\u03c3/m) \u2264 1 cm\u00b2 g\u207b\u00b9 but they are still consistent with observed galaxy sizes and masses. In addition, as a result of the steeper central density profiles developed in dSIDM, the sub-kpc circular velocities of isolated dwarfs in models with (\u03c3/m) \u2265 0.1 cm\u00b2 g\u207b\u00b9 are enhanced by about a factor of two, which are still consistent with the measured stellar velocity dispersions of Local Group dwarfs but in tension with the HI rotation curves of more massive field dwarfs. Meanwhile, for satellites of the simulated Milky Way-mass hosts, the median circular velocity profiles are marginally affected by dSIDM physics, but dSIDM may help address the missing compact dwarf satellites in CDM. 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 constant cross-section (\u03c3/m) \u2273 0.1 cm\u00b2 g\u207b\u00b9 (assuming f_(diss) = 0.5) are effectively ruled out in bright dwarfs (M\u2095\u2090\u2097\u2092 \u223c 10\u00b9\u00b9 M_\u2299) by circular velocity constraints. However, models with lower effective cross-sections (at this halo mass/velocity scale) are still viable and can give rise to non-trivial observable signatures.", "doi": "10.48550/arXiv.2206.05327", "publisher": "arXiv", "publication_date": "2022-06-10" }, { "id": "authors:egpbs-whe64", "collection": "authors", "collection_id": "egpbs-whe64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-222018454", "type": "monograph", "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 analyze the magnetic fields in a set of high-resolution, magneto-hydrodynamic, 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 ionised 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 circum-galactic medium (CGM). We find that equipartition between magnetic and cosmic ray energy densities may be valid at large (> 1 kpc) scales for typical ISM densities of Milky-Way-like galaxies, but not in their halos. Within the ISM, the magnetic fields in our simulated galaxies follow a power-law scaling with gas density. The scaling extends down to hydrogen number densities < 300 cm\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 10-200 kpc and better constrain theoretical predictions.", "doi": "10.48550/arXiv.2206.04764", "publisher": "arXiv", "publication_date": "2022-06-09" }, { "id": "authors:9vkxb-qca81", "collection": "authors", "collection_id": "9vkxb-qca81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-222021832", "type": "monograph", "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 prescribed Gaussian forcing and by a planet in two-dimensional, shearing box simulations. We show analytically and numerically that when traveling through Gaussian-like gas perturbations, dust grains are expected to clump not at the formal center of the gas pressure bump but at least 1--2 gas scale heights away, so that with the non-zero relative velocities between gas and grains, drag-induced instabilities can remain active. Over time, the dust feedback complicates the gas pressure profile, creating multiple local maxima. These dust rings are long-lived except when forced by a planet whereby particles with Stokes parameter \u03c4\u209b \u2272 0.05 are advected out of the ring within a few drift timescales. Scaled to the properties of ALMA disks, we find that if a dust clump massive enough to trigger pebble accretion is nucleated in our simulated dust rings, then such a clump would ingest the entire dust ring well within \u223c1 Myr. To ensure the survival of the dust rings, we favor a non-planetary origin and typical grain size \u03c4\u209b < 0.05. 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": "10.48550/arXiv.2206.01219", "publisher": "arXiv", "publication_date": "2022-06-02" }, { "id": "authors:6knr8-yk393", "collection": "authors", "collection_id": "6knr8-yk393", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-222025211", "type": "monograph", "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 at high numerical resolution as part of the Feedback in Realistic Environments project. FIREbox, the principal simulation of the present suite, provides a representative sample of galaxies (~1000 galaxies with M\u209b\u209c\u2090\u1d63 > 10^8 M_\u2299 at z = 0) at a resolution (~ 20 pc, m_b ~ 6 x 10\u2074 M_\u2299) comparable to state-of-the-art galaxy zoom-in simulations. Furthermore, 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 (~10\u2076) and the inclusion of multi-channel stellar feedback. Here, we focus on validating the predictions of FIREbox by comparing to observational data. We find that, at a given stellar mass (for M\u209b\u209c\u2090\u1d63 < 10^(10.5-11) M_\u2299), simulated galaxies have star formation rates, atomic and molecular gas masses, gas phase and stellar metallicities in broad agreement with observations. In addition, FIREbox shows that these galaxy scaling relations extend to the low mass regime (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 ~ 0-5. At low z, FIREbox predicts a peak in the stellar-mass--halo-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 modeling challenges to be addressed in next generation galaxy simulations.", "doi": "10.48550/arXiv.2205.15325", "publisher": "arXiv", "publication_date": "2022-05-30" }, { "id": "authors:1y7w7-few09", "collection": "authors", "collection_id": "1y7w7-few09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-222028862", "type": "monograph", "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-Claude-Andr\u00e9" }, { "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. In this work we present simulations from the STARFORGE project that are the first cloud-scale RMHD 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 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. 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. The characteristic stellar mass depends weakly on metallicity and the interstellar radiation field. Finally, while turbulent driving and the level of magnetization strongly influences the star formation history, they only influence the high-mass slope of the IMF.", "doi": "10.48550/arXiv.2205.10413", "publisher": "arXiv", "publication_date": "2022-05-20" }, { "id": "authors:esh58-8a929", "collection": "authors", "collection_id": "esh58-8a929", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-222035623", "type": "monograph", "title": "Exploring supermassive black hole physics and galaxy quenching across halo mass in FIRE cosmological zoom simulations", "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": "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": "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": "Hayward", "given_name": "Christopher C.", "orcid": "0000-0003-4073-3236", "clpid": "Hayward-Christopher-C" }, { "family_name": "Kere\u0161", "given_name": "Du\u0161an", "orcid": "0000-0002-1666-7067", "clpid": "Kere\u0161-Du\u0161an" }, { "family_name": "Su", "given_name": "Kung-Yi", "orcid": "0000-0003-1598-0083", "clpid": "Su-Kung-Yi" }, { "family_name": "Wetzel", "given_name": "Andrew", "orcid": "0000-0003-0603-8942", "clpid": "Wetzel-Andrew-R" } ], "abstract": "Feedback from accreting supermassive black holes (SMBHs) is thought to be a primary driver of quenching in massive galaxies, but the best way to implement SMBH physics into galaxy formation simulations remains ambiguous. As part of the Feedback in Realistic Environments (FIRE) project, we explore the effects of different modeling choices for SMBH accretion and feedback in a suite of \u223c500 cosmological zoom-in simulations across a wide range of halo mass (10\u00b9\u2070-10\u00b9\u00b3 M_\u2299). Within the suite, we vary the numerical schemes for BH accretion and feedback, the accretion efficiency, and the strength of mechanical, radiative, and cosmic ray feedback independently. We then compare the outcomes to observed galaxy scaling relations. We find several models that satisfy the observational constraints, and for which the energetics in different feedback channels are physically plausible. Interestingly, cosmic rays accelerated by SMBHs play an important role in many successful models. However, it is non-trivial to reproduce scaling relations across halo mass, and many model variations produce qualitatively incorrect results regardless of parameter choices. The growth of stellar and BH mass are closely related: for example, over-massive BHs tend to over-quench galaxies. BH mass is most strongly affected by the choice of accretion efficiency in high-mass halos, but by feedback efficiency in low-mass halos. The amount of star formation suppression by SMBH feedback in low-mass halos is determined primarily by the time-integrated feedback energy. For massive galaxies, the \"responsiveness\" of a model (i.e. how quickly and powerfully the BH responds to gas available for accretion) is an additional important factor for quenching.", "doi": "10.48550/arXiv.2203.06201", "publisher": "arXiv", "publication_date": "2022-03-11" }, { "id": "authors:8hs9v-27a69", "collection": "authors", "collection_id": "8hs9v-27a69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-222038999", "type": "monograph", "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 a rapid (< ~1 Gyr) emergence of a rotationally-supported interstellar medium (ISM).In the late phase with steady SFR, the rotational energy comprises > ~90% of the total kinetic + thermal energy in the ISM, and is roughly half the gravitational energy. By contrast, during the early phase with bursty star formation, the ISM has a quasi-spheroidal morphology and its energy budget is dominated by quasi-isotropic flows including turbulence and coherent inflows/outflows. This result, that rotational support is subdominant at early times, challenges the common application of equilibrium disc models to the high-redshift progenitors of Milky Way-like galaxies. We further find that the formation of a rotation-supported ISM coincides with the formation of a thermal energy-supported inner circumgalactic medium (CGM). Before this transition, the inner CGM is also supported by turbulence and coherent flows, indicating that at early times there is no clear boundary between the ISM and inner CGM.", "doi": "10.48550/arXiv.2203.04321", "publisher": "arXiv", "publication_date": "2022-03-08" }, { "id": "authors:54j5x-1ap69", "collection": "authors", "collection_id": "54j5x-1ap69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-222042376", "type": "monograph", "title": "FIRE-3: Updated Stellar Evolution Models, Yields, & Microphysics and Fitting Functions for Applications in Galaxy Simulations", "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": "Wheeler", "given_name": "Coral", "clpid": "Wheeler-Coral-R" }, { "family_name": "Sanderson", "given_name": "Robyn", "orcid": "0000-0003-3939-3297", "clpid": "Sanderson-Robyn-E" }, { "family_name": "Grudi\u0107", "given_name": "Michael Y.", "orcid": "0000-0002-1655-5604", "clpid": "Grudi\u0107-Michael-Y" }, { "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": "Orr", "given_name": "Matthew", "orcid": "0000-0003-1053-3081", "clpid": "Orr-Matthew-E" }, { "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-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": "Su", "given_name": "Kung-Yi", "orcid": "0000-0003-1598-0083", "clpid": "Su-Kung-Yi" }, { "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": "Bullock", "given_name": "James S.", "orcid": "0000-0003-4298-5082", "clpid": "Bullock-James-S" }, { "family_name": "Loebman", "given_name": "Sarah R.", "orcid": "0000-0003-3217-5967", "clpid": "Loebman-Sarah-R" }, { "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": "Necib", "given_name": "Lina", "orcid": "0000-0003-2806-1414", "clpid": "Necib-Lina" }, { "family_name": "Hayward", "given_name": "Christopher C.", "orcid": "0000-0003-4073-3236", "clpid": "Hayward-Christopher-C" } ], "abstract": "Increasingly, uncertainties in predictions from galaxy formation simulations (at sub-Milky Way masses) are dominated by uncertainties in stellar evolution inputs. In this paper, we present the full set of updates from the FIRE-2 version of the Feedback In Realistic Environments (FIRE) project code, to the next version, FIRE-3. While the transition from FIRE-1 to FIRE-2 focused on improving numerical methods, here we update the stellar evolution tracks used to determine stellar feedback inputs, e.g. stellar mass-loss (O/B and AGB), spectra (luminosities and ionization rates), and supernova rates (core-collapse and Ia), as well as detailed mass-dependent yields. We also update the low-temperature cooling and chemistry, to enable improved accuracy at T \u2272 10\u2074 K and densities n \u226b 1 cm\u207b\u00b3, and the meta-galactic ionizing background. All of these synthesize newer empirical constraints on these quantities and updated stellar evolution and yield models from a number of groups, addressing different aspects of stellar evolution. To make the updated models as accessible as possible, we provide fitting functions for all of the relevant updated tracks, yields, etc, in a form specifically designed so they can be directly 'plugged in' to existing galaxy formation simulations. We also summarize the default FIRE-3 implementations of 'optional' physics, including spectrally-resolved cosmic rays and supermassive black hole growth and feedback.", "doi": "10.48550/arXiv.2203.00040", "publisher": "arXiv", "publication_date": "2022-02-28" }, { "id": "authors:bv6j5-1ps77", "collection": "authors", "collection_id": "bv6j5-1ps77", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220816-222045764", "type": "monograph", "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-Benjamin-J" }, { "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" } ], "abstract": "Type Ia supernovae play a critical role in stellar feedback and elemental enrichment in galaxies. Recent transient surveys like the All-Sky Automated Survey for Supernova (ASAS-SN) and the Dark Energy Survey (DES) find that the specific Ia rate at z ~ 0 may be ~ 15-50 times higher in lower-mass galaxies than at Milky Way-mass. Independently, Milky Way observations show that the close-binary fraction of solar-type stars is higher at lower metallicity. Motivated by these observations, we use the FIRE-2 cosmological zoom-in simulations to explore the impact of varying Ia rate models, including metallicity dependence, on galaxies across a range of stellar masses: 10\u2077 M_\u2299 - 10\u00b9\u00b9 M_\u2299. First, we benchmark our simulated star-formation histories (SFHs) against observations. We show that assumed SFHs and stellar mass functions play a major role in determining the degree of tension between observations and metallicity-independent Ia rate models, and potentially cause ASAS-SN and DES observations to be much more consistent with each other than might naively appear. Models in which the Ia rate increases with decreasing metallicity (as ~ Z^(-0.5) to Z\u207b\u00b9) provide significantly better agreement with observations. Encouragingly, these increases in Ia rate (> 10x in low-mass galaxies) do not significantly impact galaxy stellar masses and morphologies: effective radii, axis ratios, and \u03bd/\u03c3 remain largely unaffected except for our most extreme rate models. We explore implications for both [Fe/H] and [\u03b1/Fe] enrichment: metallicity-dependent Ia rate models can improve agreement with observed stellar mass-metallicity relations in low-mass galaxies. Our results demonstrate that a wide range of metallicity-dependent Ia models are viable for galaxy formation and motivate future work in this area.", "doi": "10.48550/arXiv.2202.10477", "publisher": "arXiv", "publication_date": "2022-02-21" }, { "id": "authors:0fap0-n5w34", "collection": "authors", "collection_id": "0fap0-n5w34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183322835", "type": "monograph", "title": "An accurate treatment of scattering and diffusion in piecewise power-law models for cosmic ray and radiation/neutrino transport", "author": [ { "family_name": "Hopkins", "given_name": "Philip F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" } ], "abstract": "A popular numerical method to model the dynamics of a 'full spectrum' of cosmic rays (CRs), also applicable to radiation/neutrino hydrodynamics (RHD), is to discretize the spectrum at each location/cell as a piecewise power law in 'bins' of momentum (or frequency) space. This gives rise to a pair of conserved quantities (e.g. CR number and energy) which are exchanged between cells or bins, that in turn give the update to the normalization and slope of the spectrum in each bin. While these methods can be evolved exactly in momentum-space (considering injection, absorption, continuous losses/gains), numerical challenges arise dealing with spatial fluxes, if the scattering rates depend on momentum. This has often been treated by either by neglecting variation of those rates 'within the bin,' or sacrificing conservation -- introducing significant errors. Here, we derive a rigorous treatment of these terms, and show that the variation within the bin can be accounted for accurately with a simple set of scalar correction coefficients that can be written entirely in terms of other, explicitly-evolved 'bin-integrated' quantities. This eliminates the relevant errors without added computational cost, has no effect on the numerical stability of the method, and retains manifest conservation. We derive correction terms both for methods which explicitly integrate flux variables (two-moment or M1-like) methods, as well as single-moment (advection-diffusion, FLD-like) methods, and approximate corrections valid in various limits.", "doi": "10.48550/arXiv.2202.05283", "publisher": "arXiv", "publication_date": "2022-02-10" }, { "id": "authors:qmaft-fc563", "collection": "authors", "collection_id": "qmaft-fc563", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183308775", "type": "monograph", "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 ~MeV-TeV, these fluctuations are usually attributed either to 'extrinsic turbulence' (ET) -- a cascade from larger scales -- or 'self-confinement' (SC) -- 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-Alfvenic 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": "10.48550/arXiv.2112.02153", "publisher": "arXiv", "publication_date": "2021-12-03" }, { "id": "authors:58093-bsh88", "collection": "authors", "collection_id": "58093-bsh88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183302037", "type": "monograph", "title": "Accurately Incorporating a Reduced-Speed-of-Light in Magnetohydrodynamic-Particle-in-Cell Simulations", "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 usually adopted in magnetohydrodynamic (MHD)-particle-in-cell (PIC) simulations, in which relativistic cosmic ray (CR) particles moving at nearly the speed of light c and background (non-relativistic) plasma are evolved concurrently. With a RSOL, some \"in-code\" speed-of-light c\u0303 is set to much lower values than the true c, allowing simulations to take larger timesteps (which are restricted by the Courant condition given the large CR speeds). However, due to the absence of a well-formulated RSOL implementation in the literature for MHD-PIC simulations, the CR properties in simulations (e.g.\\ CR energy or momentum density, gyro radius) vary artificially with respect to each other and with respect to the converged (c\u0303 \u2192c) solutions with different implementations of a RSOL, breaking the correspondence between simulation results and physical reality. Here, we derive a new formulation of the MHD-PIC equations with a 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\u0303 even for c\u0303 \u226ac, (2) ensures that the simulation can simultaneously represent the real physical values of CR number, mass, momentum, and energy density, (3) retains the correct physical meaning of various terms like the electric field, and (4) ensures the numerical timestep for CRs can always be safely increased by a factor \u223cc/c\u0303 . This should enable greater self-consistency and reduced CPU cost in simulations of CR-MHD interactions.", "doi": "10.48550/arXiv.2111.14704", "publisher": "arXiv", "publication_date": "2021-11-29" }, { "id": "authors:27x61-60j20", "collection": "authors", "collection_id": "27x61-60j20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183258700", "type": "monograph", "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.", "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 AGB or RCB-like stars, dust is accelerated by radiation from the star and coupled to the gas via collisional drag forces. But 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 (\u223c10\u221220% 1\u03c3-level) in the extinction, corresponding to \u223c0.1\u22121mag level in the stellar types above, on timescales of order months to a year. The fluctuations are surprisingly robust to finite source-size effects 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 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": "10.48550/arXiv.2111.09335", "publisher": "arXiv", "publication_date": "2021-11-17" }, { "id": "authors:f3st0-avj77", "collection": "authors", "collection_id": "f3st0-avj77", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183255347", "type": "monograph", "title": "Amplified J-factors in the Galactic Center for velocity-dependent darkmatter annihilation in FIRE simulations", "author": [ { "family_name": "McKeown", "given_name": "Daniel", "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 halos to calculate astrophysical J-factors for dark matter annihilation and indirect detection studies. In addition to velocity-independent (s-wave) annihilation cross sections \u03c3_v, we also calculate effective J-factors for velocity-dependent models, where the annihilation cross section is either either p-wave (\u221dv\u00b2/c\u00b2) or d-wave (\u221dv\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\u22124. They also have a larger range of central (\u223c400 pc) dark matter densities than the DMO runs (\u03c1_(FIRE)/\u03c1_(DMO) \u2243 0.5\u22123) owing to the competing effects of baryonic contraction and feedback. At 3 degrees from the Galactic Center, FIRE J-factors are 5\u221250 (p-wave) and 15\u2212500 (d-wave) times higher than in the DMO runs. The change in s-wave signal at 3 degrees is more modest and can be higher or lower (\u223c0.3\u22126), though the shape of the emission profile is flatter (less peaked towards the Galactic Center) 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": "10.48550/arXiv.2111.03076", "publisher": "arXiv", "publication_date": "2021-11-04" }, { "id": "authors:0sv2b-hnv88", "collection": "authors", "collection_id": "0sv2b-hnv88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183251991", "type": "monograph", "title": "Probing Hot Gas Components of Circumgalactic Medium in Cosmological Simulations with the Thermal Sunyaev-Zel'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-Zel'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 nuclei (AGN) activity in galaxies, participating in the feedback loop that regulates star and black hole mass growth in galaxies.\nWe 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 tSZ signal and halo mass and 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 the 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": "10.48550/arXiv.2110.15381", "publisher": "arXiv", "publication_date": "2021-10-28" }, { "id": "authors:ztxrx-53f70", "collection": "authors", "collection_id": "ztxrx-53f70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183248631", "type": "monograph", "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-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 first simulations evolving resolved spectra of cosmic rays (CRs) from MeV-TeV energies (including electrons, positrons, (anti)protons, and heavier nuclei), in live kinetic-MHD 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-neighborhood (LISM) observations (spectra, B/C, e\u207a/e\u207b, p\u0305/p, \u00b9\u2070Be/\u2079Be, ionization). 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 circum-galactic medium in realistic galaxies necessarily imposes a ~10kpc 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 ~0.1-1 kpc 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-Taylor stages of SNe remnants.", "doi": "10.48550/arXiv.2109.09762", "publisher": "arXiv", "publication_date": "2021-09-20" }, { "id": "authors:gchgq-nra93", "collection": "authors", "collection_id": "gchgq-nra93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183241907", "type": "monograph", "title": "Dust in the Wind with Resonant Drag Instabilities: I. The Dynamics of Dust-Driven Outflows in GMCs and HII 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.", "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 nonlinear 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), HII 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 nonlinear on timescales 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 HII 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": "10.48550/arXiv.2107.04608", "publisher": "arXiv", "publication_date": "2021-07-09" }, { "id": "authors:ywveb-t6m83", "collection": "authors", "collection_id": "ywveb-t6m83", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183238549", "type": "monograph", "title": "Trinity I: Self-Consistently Modeling the Dark Matter Halo-Galaxy-Supermassive Black Hole Connection from z = 0\u221210", "author": [ { "family_name": "Zhang", "given_name": "Haowen", "clpid": "Zhang-Haowen" }, { "family_name": "Behroozi", "given_name": "Peter", "orcid": "0000-0002-2517-6446", "clpid": "Behroozi-Peter-S" }, { "family_name": "Volonteri", "given_name": "Marta", "orcid": "0000-0002-3216-1322", "clpid": "Volonteri-Marta" }, { "family_name": "Silk", "given_name": "Joseph", "clpid": "Silk-Joseph" }, { "family_name": "Fan", "given_name": "Xiaohui", "orcid": "0000-0003-3310-0131", "clpid": "Fan-Xiaohui" }, { "family_name": "Hopkins", "given_name": "Philip F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" }, { "family_name": "Yang", "given_name": "Jinyi", "orcid": "0000-0001-5287-4242", "clpid": "Yang-Jinyi" }, { "family_name": "Aird", "given_name": "James", "orcid": "0000-0003-1908-8463", "clpid": "Aird-James-A" } ], "abstract": "We present Trinity, a flexible empirical model that self-consistently infers the statistical connection between dark matter haloes, galaxies, and supermassive black holes (SMBHs). Trinity is constrained by galaxy observables from 0 < z < 10 (galaxies' stellar mass functions, specific and cosmic SFRs, quenched fractions, and UV luminosity functions) and SMBH observables from 0 < z < 6.5 (quasar luminosity functions, quasar probability distribution functions, active black hole mass functions, local SMBH mass-bulge mass relations, and the observed SMBH mass distributions of high redshift bright quasars). The model includes full treatment of observational systematics (e.g., AGN obscuration and errors in stellar masses). From these data, Trinity infers the average SMBH mass, SMBH accretion rate, merger rate, and Eddington ratio distribution as functions of halo mass, galaxy stellar mass, and redshift. Key findings include: 1) the normalization of the SMBH mass-bulge mass relation increases only mildly from z = 0 to z = 3, but decreases more strongly from z = 3 to z = 10; 2) The AGN radiative+kinetic efficiency is \u223c0.04-0.07, and does not show significant redshift dependence given the existing data constraints; 3) AGNs show downsizing, i.e., the Eddington ratios of more massive SMBHs start to decrease earlier than those of lower-mass objects; 4) The average ratio between average SMBH accretion rate and SFR is \u223c10\u207b\u00b3 for low-mass galaxies, which are primarily star-forming. This ratio increases to \u223c10\u207b\u00b9 for the most massive haloes below z \u223c 1, where star formation is quenched but SMBHs continue to accrete.", "doi": "10.48550/arXiv.2105.10474", "publisher": "arXiv", "publication_date": "2021-05-21" }, { "id": "authors:j5hkf-zhf82", "collection": "authors", "collection_id": "j5hkf-zhf82", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220228-183235199", "type": "monograph", "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-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": "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 \u03c3/m. We compare the shape of the main dark matter (DM) halo at redshift z = 0 predicted by SIDM simulations (at \u03c3/m = 0.1, 1, and 10 cm\u00b2 g\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 in the MW.", "doi": "10.48550/arXiv.2104.14069", "publisher": "arXiv", "publication_date": "2021-04-29" }, { "id": "authors:6zv4x-jah97", "collection": "authors", "collection_id": "6zv4x-jah97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200310-104835304", "type": "monograph", "title": "Swirls of FIRE: Spatially Resolved Gas Velocity Dispersions and Star Formation Rates in FIRE-2 Disk 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": "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": "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)--star formation rate (SFR) relation in the FIRE-2 (Feedback in Realistic Environments) cosmological simulations. We specifically focus on Milky Way mass disk galaxies at late times. In agreement with observations, we find a relatively flat relationship, with \u03c3 \u2248 15\u221230 km/s 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-\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 timescales of 10-100 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 disk (Toomre's Q=1) model predictions, and the data effectively rule out models assuming that gas turns into stars at (low) constant efficiency (i.e., 1% 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 strongly subdominant to stellar feedback in the simulated galaxy disks.", "doi": "10.48550/arXiv.1911.00020", "publisher": "arXiv", "publication_date": "2019-10-31" }, { "id": "authors:5v5v6-xsb27", "collection": "authors", "collection_id": "5v5v6-xsb27", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105610955", "type": "monograph", "title": "Nonlinear 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-gas 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 behavior is characterized by three regimes - high, intermediate, and low wavenumbers - the boundary between which is determined by the dust-gas 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 behaviors are qualitatively different from those of dust 'passively' driven by external hydrodynamic turbulence, with no back-reaction force from dust onto 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": "10.48550/arXiv.1810.08214", "publisher": "arXiv", "publication_date": "2018-10-18" }, { "id": "authors:2x0tv-4zm31", "collection": "authors", "collection_id": "2x0tv-4zm31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105600152", "type": "monograph", "title": "The Elephant in the Room: The Importance of Where and When Massive Stars Form in Molecular Clouds", "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" } ], "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 ~3) 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 where and how massive stars form, and this remains deeply uncertain in star formation theory.", "doi": "10.48550/arXiv.1809.08344", "publisher": "arXiv", "publication_date": "2018-09-21" }, { "id": "authors:001w2-ns502", "collection": "authors", "collection_id": "001w2-ns502", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190206-105545425", "type": "monograph", "title": "The effects of metallicity and cooling physics on fragmentation: implications on direct-collapse black hole formation", "author": [ { "family_name": "Moran", "given_name": "C. Corbett", "orcid": "0000-0003-2088-7465", "clpid": "Moran-C-C" }, { "family_name": "Grudi\u0107", "given_name": "M. Y.", "clpid": "Grudi\u0107-M-Y" }, { "family_name": "Hopkins", "given_name": "P. F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" } ], "abstract": "A promising supermassive black hole seed formation channel is that of direct collapse from primordial gas clouds. We perform a suite of 3D hydrodynamics simulations of an isolated turbulent gas cloud to investigate conditions conducive to forming massive black hole seeds via direct collapse, probing the impact of cloud metallicity, gas temperature floor and cooling physics on cloud fragmentation. We find there is no threshold in metallicity which produces a sharp drop in fragmentation. When molecular cooling is not present, metallicity has little effect on fragmentation. When molecular cooling is present, fragmentation is suppressed by at most \u223c25%, with the greatest suppression seen at metallicities below 2% solar. A gas temperature floor \u223c10^4 K produces the largest drop in fragmentation of any parameter choice, reducing fragmentation by \u223c60%. At metallicities below 2% solar or at temperatures \u223c10^3 K we see a reduction in fragmentation \u223c20\u221225%. For a cloud of metallicity 2% solar above and a temperature below 10^3 K, the detailed choices of temperature floor, metallicity, and cooling physics have little impact on fragmentation.", "doi": "10.48550/arXiv.1803.06430", "publisher": "arXiv", "publication_date": "2018-03-17" }, { "id": "authors:d6zy3-ntd12", "collection": "authors", "collection_id": "d6zy3-ntd12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181220-112910388", "type": "monograph", "title": "A New Public Release of the GIZMO Code", "author": [ { "family_name": "Hopkins", "given_name": "Philip F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" } ], "abstract": "We describe a major update to the public GIZMO code. GIZMO has been used in simulations of cosmology; galaxy and star formation and evolution; black hole accretion and feedback; proto-stellar disk dynamics and planet formation; fluid dynamics and plasma physics; dust-gas dynamics; giant impacts and solid-body interactions; collisionless gravitational dynamics; and more. This release of the public code supports: hydrodynamics (using various mesh-free finite-volume Godunov methods or SPH), ideal and non-ideal MHD, anisotropic conduction and viscosity, radiative cooling and chemistry, star and black hole formation and feedback, sink particles, dust-gas (aero)-dynamics (with or without magnetic fields), elastic/plastic dynamics, arbitrary (gas, stellar, degenerate, solid/liquid material) equations of state, passive scalar/turbulent diffusion, large-eddy and shearing boxes, self-gravity with fully-adaptive force softenings, arbitrary cosmological expansion, and on-the-fly group-finding. It is massively-parallel with hybrid MPI+OpenMP scaling verified up to >1 million threads. The code is extensively documented, with test problems and tutorials provided for these different physics modules.", "doi": "10.48550/arXiv.1712.01294", "publisher": "arXiv", "publication_date": "2017-12-04" }, { "id": "authors:4n68g-16885", "collection": "authors", "collection_id": "4n68g-16885", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160106-114305351", "type": "monograph", "title": "Bridging the Gap: Observations and Theory of Star Formation Meet on Large and Small Scales", "author": [ { "family_name": "Pineda", "given_name": "Jorge L.", "orcid": "0000-0001-8898-2800", "clpid": "Pineda-J-L" }, { "family_name": "Hopkins", "given_name": "Philip F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" } ], "abstract": "The drive to understand galaxy formation and evolution over the lifetime of the universe has justified vast space-based and ground-based telescope facilities, as well as the development of new technologies. The details of star formation, and the modes by which that activity couples to the broader galactic environment, occurs on small spatial scales. These scales can only be traced with great sophistication in the local universe, as witnessed by observations using the Spitzer Space Telescope, the Herschel Space Observatory, the Stratospheric Observatory for Infrared Astronomy (SOFIA), and the Atacama Large Millimeter Array (ALMA). A critical realization of the last decade, however, is that the large scales and small scales are strongly coupled, and cannot be treated in isolation. At the same time, the scales studied in the local universe are \"sub-grid\"\nfor the purpose of cosmological simulations that make valiant efforts to include the physics of star formation and its feedback to the local environment. The fundamental uncertainties in how this sub-grid physics is incorporated into the larger picture are by far the greatest limitation in understanding galaxy formation and evolution. \n\nThe main goal of cosmological simulations is to understand the formation and evolution of the universe over a wide range of scales going from the Hubble volume to sub-light-year scales within galaxies. However, due to computational limitations, the physics of star formation in galaxies and the effects this process has on the formation and evolution of galaxies are often greatly simplified.\nFor instance, accounting for the effect of stellar feedback in cosmological simulations is a crucial factor in galaxy formation and evolution. Without stellar feedback in galaxies, the gas would rapidly cool and collapse, converting all available gas into stars within a dynamical time. This consequence is in sharp conflict with observations\u2014there are vastly fewer stars in our universe\nthan the models would predict. Until recently, numerical simulations have been unable to regulate star formation efficiently enough to reproduce observations, with many consequences: models with too many stars also predict they form at the wrong times in the universe's history, that there are the wrong abundances of heavy elements, that galaxies look nothing like the Milky Way, and even that the observable properties of dark matter are (apparently) discordant with new\nprecision-cosmology measurements. All of these problems may, in fact, be due to the fundamental problem of understanding how small and large scales interact.", "doi": "10.26206/ZCVD-7P40", "publisher": "Keck Institute for Space Studies", "publication_date": "2015-12" } ]