Electronic noise, or stochasticity in the current, voltage, and frequency of a carrier signal is caused by microscopic fluctuations in the occupation of quantum electronic states. In the context of scientific instrumentation, understanding the physical origin of these fluctuations is of paramount importance since the associated stochasticity ultimately limits the fidelity of information transmitted through electronically processed-signals. The unifying theme of the work presented in this thesis is the study of electronic fluctuations in semiconductor materials and devices. Our interest in this topic is twofold. First, while the Nyquist law dictates the equivalence of noise and transport properties for systems in thermal equilibrium, this relationship breaks down for systems driven out of equilibrium by external forcing. Simulating non-equilibrium electronic fluctuations can therefore provide new insights into the microscopic processes that control energy and momentum relaxation which would not be available from conventional studies of transport alone. Furthermore, because noise properties are sensitive to the microscopic details of the bandstructure and scattering, ab initio simulations of noise observables provide a more rigorous test of the accepted theory of charge transport and carrier scattering in materials. Second, cryogenic low noise amplifiers based on high electron mobility transistors (HEMTs) are widely used in electromagnetic detector chains in applications such as radio astronomy, deep space communications, and quantum computing. The design and optimization of HEMT devices have conventionally relied upon empirical circuit-level models of fluctuations in devices. As the noise performance of modern low-noise amplifiers has saturated to levels five to ten times above the standard quantum limit, these empirical models are unable to resolve the microscopic origin of the limiting excess noise. Identifying the microscopic mechanisms underpinning noise in modern amplifiers is therefore necessary to produce better devices for scientific instrumentation. In this work, we investigate electronic noise in semiconductor materials and devices with a combination of first-principles simulations and Schottky thermometry experiments in transistor amplifiers.
\r\n\r\nFirst, we present our work on the development of novel parameter-free simulations of non-equilibrium noise in semiconductor materials. While the ab initio theory of low-field electronic transport properties such as carrier mobility is well-established, an equivalent treatment of electronic fluctuations about a non-equilibrium steady state has remained less explored. Starting from the Boltzmann Transport Equation, we develop an ab initio method for hot electron noise in semiconductors. In contrast with the typical numerical methods used for electronic noise such as Monte Carlo techniques, no adjustable parameters are required in the present formalism with the electronic band structure and scattering rates calculated from first-principles. Our formalism enables a parameter-free approach to probe the microscopic transport processes that give rise to electronic noise in semiconductors. Next, we apply the developed method to compute the spectral noise power in two materials of technological interest, GaAs and Si. In our first study in GaAs, we show that despite the well-known dominance of optical phonon scattering, the spectral features in AC transport properties and noise originate from a surprising quasi-elasticity in the scattering of warm electrons with the lattice. In our second study, we apply the method to Si which possesses a more complicated multivalley conduction band. This study demonstrates that the widely-accepted one-phonon scattering approximation is insufficient to reproduce the warm electron tensor and that incorporating second-order mechanisms, such as two-phonon scattering, may be critical to obtain an accurate description of noise in such materials.
\r\n \r\nFinally, we discuss our work on developing deeper understandings of electronic noise in real devices with a focus on transistor amplifiers. While the first-principles work described above is appropriate for evaluating noise in ideal materials, in real semiconductor devices, charge carriers are influenced by mechanisms such as defect scattering, size effects, and reflections at interfaces. Owing to the complexity of these mechanisms, HEMT noise is typically treated with empirical models, where the physical noise sources are reduced to fitting parameters. Existing models of HEMT noise, such as the Pospieszalski model, are unable to resolve the mechanisms that set the noise floor of modern transistor amplifiers. In particular, the magnitude of the contribution of thermal noise from the gate at cryogenic temperatures remains unclear owing to a lack of experimental measurements of thermal resistance under these conditions. We report measurements of gate junction temperature and thermal resistance in a HEMT at cryogenic and room temperatures using a Schottky thermometry method. Based on our findings, we develop a phonon radiation model of heat transfer in the device and estimate that the thermal noise from the gate is several times larger than previously assumed. Our work suggests that self-heating results in a practical lower limit for the microwave noise figure of HEMTs at cryogenic temperatures.
", "doi": "10.7907/tba0-pd94", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14638", "collection": "thesis", "collection_id": "14638", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05272022-180844058", "primary_object_url": { "basename": "ArdizziAnthony_Thesis2022_Submitted.pdf", "content": "final", "filesize": 23142248, "license": "other", "mime_type": "application/pdf", "url": "/14638/1/ArdizziAnthony_Thesis2022_Submitted.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Self-Heating of HEMT Low-Noise Amplifiers in Liquid Cryogenic Environments and the Limits of Microwave Noise Performance", "author": [ { "family_name": "Ardizzi", "given_name": "Anthony Joseph", "orcid": "0000-0001-8667-1208", "clpid": "Ardizzi-Anthony-Joseph" } ], "thesis_advisor": [ { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" }, { "family_name": "Schwab", "given_name": "Keith C.", "orcid": "0000-0001-8216-4815", "clpid": "Schwab-K-C" } ], "thesis_committee": [ { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" }, { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Schwab", "given_name": "Keith C.", "orcid": "0000-0001-8216-4815", "clpid": "Schwab-K-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Detection and processing of microwave signals is of substantial scientific importance in fields ranging from radio astronomy to quantum computing. An essential component of the signal processing chain is the microwave amplifier, which adds gain to the signal so that it may be processed by subsequent microwave components. However, the amplifier itself adds its own internally generated noise into the measurement chain. As a result, amplifiers which add a minimal amount of noise are crucial to any high precision measurement scheme. A device which is commonly employed for this task is the high-electron-mobility transistor (HEMT) amplifier. Understanding the fundamental limits of the microwave noise performance of HEMT amplifiers is highly desirable. Noise temperatures in these devices as low as 3 times the quantum limit have been observed in the last decade, but the lack of understanding of the origin of the excess noise has hindered further improvements. Noise in HEMTs is attributed to a generator at the output, known as drain noise; and a generator at the input, which is attributed to thermal noise of the gate. At cryogenic temperatures of ~4 K, thermal noise is predicted to be negligible. However, a plateau in noise temperature has been observed at physical temperatures below ~20 K, with a negligible improvement in noise performance upon further cooling.
\r\n \r\nThe primary noise mechanism responsible for this plateau is believed to be ohmic heating of the HEMT structure induced by current in the active device channel, a process known as self-heating. At room temperature the ambient thermal noise dominates the amplifier\u2019s overall noise performance, but at the cryogenic temperatures required to achieve low-noise performance the self-heating effect produces thermal noise at the input of the HEMT gate which contributes significantly to the total noise. A potential mechanism to mitigate self-heating is to provide an additional thermal dissipation path for the Joule heating in the channel. However, given the sub-micron length scales and buried gate structure of HEMTs, thermal management is challenging. The primary heat conduction pathway, that of phonons travelling through the bulk HEMT substrate, decreases rapidly in magnitude at cryogenic temperatures. An alternative option is to submerge the HEMT in a cryogenic fluid, thereby presenting an alternate thermal conduction route through the HEMT surface into the fluid. This technique, while commonly employed in cryogenic thermal management of superconducting magnets, has not been investigated for HEMTs.
\r\n \r\nIn this work we explore the use of liquid cryogenic cooling to directly mitigate the effect of HEMT self-heating. We test in particular the effectiveness of cooling using superfluid helium-4, which has the highest known thermal conductivity of any known substance. We report a systematic experimental investigation of the noise performance of a cryogenic packaged two-stage HEMT low-noise amplifier over a wide range of biases in a 4.0 - 5.5 GHz frequency band, with the device immersed in a variety of cryogenic baths including helium-4 vapor, liquid helium-4, superfluid helium-4, and vacuum. We present the details of the experimental apparatus which was constructed to perform microwave noise measurements of the low-noise amplifier when submerged in a liquid cryogen environment. We interpret our results using a small-signal model of the amplifier and compare our findings with the predictions of a phonon radiation model of heat dissipation. We find that liquid cryogenic cooling is unable to mitigate the thermal noise associated with self-heating. Considering this finding, we examine the implications for the lower bounds of cryogenic noise performance in HEMTs by incorporating the effects of self-heating into the existing noise modelling of HEMT amplifiers. Our analysis supports the general design principle for cryogenic HEMTs of maximizing gain at the lowest possible power.
", "doi": "10.7907/9va8-tc64", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:11547", "collection": "thesis", "collection_id": "11547", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05272019-174203596", "primary_object_url": { "basename": "eastwood_michael_2019.pdf", "content": "final", "filesize": 40084935, "license": "cc_by_sa", "mime_type": "application/pdf", "url": "/11547/1/eastwood_michael_2019.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Searching for the Cosmic Dawn with the Hyperfine Structure Transition of Hydrogen", "author": [ { "family_name": "Eastwood", "given_name": "Michael William", "orcid": "0000-0002-4731-6083", "clpid": "Eastwood-Michael-William" } ], "thesis_advisor": [ { "family_name": "Hallinan", "given_name": "Gregg W.", "orcid": "0000-0002-7083-4049", "clpid": "Hallinan-G-W" } ], "thesis_committee": [ { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Hallinan", "given_name": "Gregg W.", "orcid": "0000-0002-7083-4049", "clpid": "Hallinan-G-W" }, { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Pearson", "given_name": "Timothy J.", "orcid": "0000-0001-5213-6231", "clpid": "Pearson-T-J" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "div_pma" } ], "abstract": "The 21 cm hyperfine structure transition of neutral hydrogen promises to open a window into the first billion years of the Universe (z > 6). With the exception of rare lines of sight towards exceptionally distant and luminous galaxies, this period of the universe's history remains largely unexplored. During this time the 21 cm transition is expected to be detectable as a 10--100 mK perturbation in the thermal Cosmic Microwave Background (CMB) spectrum.
\r\n\r\nDue to the large field of view of low frequency radio telescopes (typically composed of dipole antennas) and the fact that the line of sight distance can be inferred from the measured frequency of the transition, the ultimate goal of 21 cm cosmology is to produce three dimensional tomographic maps of the 21 cm brightness temperature. In this way, the formation of the first stars and galaxies will be revealed through their influence on the neutral gas around them.
\r\n\r\nThis thesis saw the construction of the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA), a new low frequency (27--85 MHz) radio telescope located near Bishop, California. Composed of 288 crossed-dipole antennas, the OVRO-LWA is capable of imaging the entire visible hemisphere in a single 13 s snapshot image with 8 arcmin angular resolution.
\r\n\r\nThe primary challenges faced by efforts to detect the highly redshifted 21 cm transition are seeing past the blinding glow of foreground radio emission that is five orders of magnitude brighter than the cosmological emission, and calibrating the instrument to a level where it's possible to make the separation between foreground emission and the 21 cm signal. In this thesis I will present foundational work using the OVRO-LWA to place upper limits on spatial fluctuations of the 21 cm transition during the Cosmic Dawn---the period of first star formation.
\r\n\r\nIn this thesis I present the highest angular resolution maps of the full sky below 100 MHz, and generated with a new widefield imaging technique that is specialized for drift scanning interferometers. These sky maps are a 10-fold improvement in angular resolution over existing maps at comparable frequencies, and are publicly available now for use in modeling and subtracting the contamination of foreground emission in 21 cm experiments.
\r\n\r\nUsing a 28 hr integration with the OVRO-LWA, I place to-date the most constraining upper limits on the amplitude of the 21 cm spatial power spectrum at the Cosmic Dawn, and the first limits at z > 18. Although the current constraints \u0394212 \u2272 (104mK)2 do not meaningfully restrict the parameter space of models of early star formation, they do inform the design and calibrations necessary for future measurements to push towards a detection of the high-redshift 21 cm transition. In making this measurement I demonstrate the application of a new foreground filter that accounts for the full covariance of the foreground emission, and provide an updated measurement of the foreground angular covariance. Finally, I interpret the limiting factors in this measurement and determine the instrumental calibration and characterization requirements the OVRO-LWA will need to achieve in order to make a detection of the 21 cm power spectrum of the Cosmic Dawn.
", "doi": "10.7907/DYPP-JP25", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:9906", "collection": "thesis", "collection_id": "9906", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08292016-174647631", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 8434177, "license": "other", "mime_type": "application/pdf", "url": "/9906/1/thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Low-Mass Stars and Their Companions", "author": [ { "family_name": "Montet", "given_name": "Benjamin Tyler", "orcid": "0000-0001-7516-8308", "clpid": "Montet-Benjamin-Tyler" } ], "thesis_advisor": [ { "family_name": "Johnson", "given_name": "John A.", "clpid": "Johnson-J-A" } ], "thesis_committee": [ { "family_name": "Hallinan", "given_name": "Gregg W.", "orcid": "0000-0002-7083-4049", "clpid": "Hallinan-G-W" }, { "family_name": "Johnson", "given_name": "John A.", "clpid": "Johnson-J-A" }, { "family_name": "Hopkins", "given_name": "Philip F.", "clpid": "Hopkins-P-F" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Knutson", "given_name": "Heather A.", "clpid": "Knutson-H-A" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "In this thesis, I present seven studies aimed towards better understanding the demographics and physical properties of M dwarfs and their companions. These studies focus in turn on planetary, brown dwarf, and stellar companions to M dwarfs.
\r\n\r\nI begin with an analysis of radial velocity and transit timing analyses of multi-transiting planetary systems, finding that if both signals are measured to sufficiently high precision the stellar and planetary masses can be measured to a high precision, eliminating a need for stellar models which may have systematic errors. I then combine long-term radial velocity monitoring and a direct imaging campaign to measure the occurrence rate of giant planets around M dwarfs. I find that 6.5 +/- 3.0% of M dwarfs host a Jupiter mass or larger planet within 20 AU, with a strong dependence on stellar metallicity.
\r\n\r\nI then present two papers analyzing the LHS 6343 system, which contains a widely separated M dwarf binary (AB). Star A hosts a transiting brown dwarf (LHS 6343 C) with a 12.7 day period. By combining radial velocity data with transit photometry, I am able to measure the mass and radius of the brown dwarf to 2% precision, the most precise measurement of a brown dwarf to date. I then analyze four secondary eclipses of the LHS 6343 AC system as observed by Spitzer in order to measure the luminosity of the brown dwarf in both Spitzer bandpasses. I find the brown dwarf is consistent with theoretical models of an 1100 K T dwarf at an age of 5 Gyr and empirical observations of field T5-6 dwarfs with temperatures of 1070 +/- 130 K. This is the first non-inflated brown dwarf with a measured mass, radius, and multi-band photometry, making it an ideal test of evolutionary models of field brown dwarfs.
\r\n\r\nNext, I present the results of an astrometric and radial velocity campaign to measure the orbit and masses of both stars in the GJ 3305 AB system, an M+M binary comoving with 51 Eridani, a more massive star with a directly imaged planetary companion. I compare the masses of both stars to largely untested theoretical models of young M dwarfs, finding that the models are consistent with the measured mass of star A but slightly overpredict the luminosity of star B.
\r\n\r\nIn the final two science chapters I focus on space-based transit surveys, present and future. First, I present the first catalog of statistically validated planets from the K2 mission, as well as updated stellar and planetary parameters for all systems with candidate planets in the first K2 field. The catalog includes K2-18b, a ``mini-Neptune'' planet that receives a stellar insolation consistent with the level that the Earth receives from the Sun, making it a useful comparison against planets of a similar size that are highly irradiated, such as GJ 1214 b. Finally, I present predictions for the WFIRST mission. While designed largely as a microlensing mission, I find it will be able to detect as many as 30,000 transiting planets towards the galactic bulge, providing information about how planet occurrence changes across the galaxy. These planets will be able to be confirmed largely through direct detection of their secondary eclipses. Moreover, I find that more than 50% of the planets it detects smaller than Neptune will be found around M dwarf hosts.
", "doi": "10.7907/Z9KW5D1R", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10294", "collection": "thesis", "collection_id": "10294", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06052017-232351957", "type": "thesis", "title": "Unveiling the Structure of Active Galactic Nuclei with Hard X-ray Spectroscopy", "author": [ { "family_name": "Balokovic", "given_name": "Mislav", "orcid": "0000-0003-0476-6647", "clpid": "Balokovic-Mislav" } ], "thesis_advisor": [ { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" } ], "thesis_committee": [ { "family_name": "Hopkins", "given_name": "Philip F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" }, { "family_name": "Hillenbrand", "given_name": "Lynne A.", "clpid": "Hillenbrand-L-A" }, { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" } ], "local_group": [ { "literal": "Space Radiation Laboratory" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Despite the long history of studies of active galactic nuclei (AGN), details of the structure of the accretion flow onto supermassive black holes are far from clear. Work presented in this thesis is directed at unveiling properties of AGN structure through broadband X-ray spectroscopy, with particular emphasis on the hard X-ray band (photon energies above 10 keV). With its unprecedented sensitivity in this energy band, the NuSTAR telescope provides the key observational diagnostics of the properties of the AGN X-ray source, the corona, and the surrounding gas in the accretion disk, the broad-line region, and the torus.
\r\n\r\nThe first study presented in this thesis focuses on measurements of the optical depth and the temperature of the plasma in the corona of an obscured AGN. Fitting theoretical spectral models for coronal emission to the NuSTAR data constrained these two basic physical parameters under the assumption of either spherical or disk-like geometry for the corona.
\r\n\r\n\r\nThe remainder of the thesis is dedicated to studies of the anisotropic obscuring structure broadly referred to as the torus. One of them is a case study of three heavily obscured AGN with spectra dominated by the X-ray light scattered and reprocessed in the torus, where it is possible to constrain one of the basic torus properties -- its globally averaged column density. The following study presents the calculation of a new spectral model for reprocessing of the intrinsic X-ray continuum within the torus. Its added flexibility compared to previously available models allows for both the average column density of the torus and its covering factor to be constrained from broadband X-ray spectra of a wide variety of AGN.
\r\n\r\n\r\nThe final part of the thesis in based on a large survey of the local obscured AGN population performed with NuSTAR. Spectral modeling of more than a hundred individual AGN, including both old and new spectral models, is presented. From analyses of the X-ray data for a large and representative AGN sample, for the first time, it is found that their tori preferentially have high covering factors and average column densities close to unity optical depth for Compton scattering.
\r\n", "doi": "10.7907/Z9WM1BG8", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10235", "collection": "thesis", "collection_id": "10235", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312017-154839851", "primary_object_url": { "basename": "Antonija_Oklopcic_thesis_2017_final.pdf", "content": "final", "filesize": 8580590, "license": "other", "mime_type": "application/pdf", "url": "/10235/3/Antonija_Oklopcic_thesis_2017_final.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Radiative Processes in Astrophysical Gases: From the Intergalactic and Interstellar Medium to Exoplanetary Atmospheres", "author": [ { "family_name": "Oklop\u010di\u0107", "given_name": "Antonija", "orcid": "0000-0002-9584-6476", "clpid": "Oklop\u010di\u0107-Antonija" } ], "thesis_advisor": [ { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" } ], "thesis_committee": [ { "family_name": "Hillenbrand", "given_name": "Lynne A.", "clpid": "Hillenbrand-L-A" }, { "family_name": "Hopkins", "given_name": "Philip F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Mawet", "given_name": "Dimitri", "orcid": "0000-0002-8895-4735", "clpid": "Mawet-D" }, { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" } ], "local_group": [ { "literal": "TAPIR" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "This thesis presents theoretical investigations in three areas of astrophysics, all related to radiative processes and interactions between stellar radiation and gaseous media in the Universe, ranging from the intergalactic and interstellar medium to planetary atmospheres.
\r\n\r\nPart I of the thesis consists of two independent investigations in which we study the effects of stellar feedback in high-redshift environments. The topic of Chapter 2 is the intergalactic medium (IGM) in the epoch just after the formation of the first stars in the Universe, but before the cosmic reionization was completed. This epoch is of great interest for the ongoing and future experiments aimed at observing the neutral IGM via the redshifted 21 cm line of hydrogen. We study the effects of resonant scattering of Lyman-\u03b1 photons produced by early stars on the structure of temperature fluctuations in the IGM. In Chapter 3, we use cosmological hydrodynamic simulations of galaxy evolution to study the effects of stellar feedback on the clumpy structure of star-forming galaxies at z ~ 2. Observations of high-redshift galaxies show that their morphology is often dominated by a few giant clumps of intense star formation, but the nature and the importance of these clumps for the evolution of their host galaxies are uncertain. We present a detailed analysis of the properties of giant clumps in a high-redshift simulated galaxy from the FIRE project.
\r\n\r\nPart II of the thesis is devoted to the effects of Raman scattering of stellar radiation in the atmospheres of extrasolar planets. Spectral signatures of Raman scattering imprinted in the geometric albedo spectrum of a gaseous planet carry information about the properties of the planet's atmosphere---its composition, temperature, and the radiation-penetration depth. In Chapter 5, we present the results of radiative transfer calculations including the treatment of Raman scattering for different types of planetary atmospheres and analyze the feasibility of detecting the spectral signatures of Raman scattering in nearby exoplanets. The structure and the intensity of Raman spectral features depends on both the atmospheric properties and the shape of the stellar spectrum irradiating the atmosphere. In Chapter 6, we analyze the diversity of Raman features in the geometric albedo spectra of planets hosted by different types of stars.
", "doi": "10.7907/Z9GM85CS", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10235", "collection": "thesis", "collection_id": "10235", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312017-154839851", "primary_object_url": { "basename": "Antonija_Oklopcic_thesis_2017_final.pdf", "content": "final", "filesize": 8580590, "license": "other", "mime_type": "application/pdf", "url": "/10235/3/Antonija_Oklopcic_thesis_2017_final.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Radiative Processes in Astrophysical Gases: From the Intergalactic and Interstellar Medium to Exoplanetary Atmospheres", "author": [ { "family_name": "Oklop\u010di\u0107", "given_name": "Antonija", "orcid": "0000-0002-9584-6476", "clpid": "Oklop\u010di\u0107-Antonija" } ], "thesis_advisor": [ { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" } ], "thesis_committee": [ { "family_name": "Hillenbrand", "given_name": "Lynne A.", "clpid": "Hillenbrand-L-A" }, { "family_name": "Hopkins", "given_name": "Philip F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Mawet", "given_name": "Dimitri", "orcid": "0000-0002-8895-4735", "clpid": "Mawet-D" }, { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" } ], "local_group": [ { "literal": "TAPIR" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "This thesis presents theoretical investigations in three areas of astrophysics, all related to radiative processes and interactions between stellar radiation and gaseous media in the Universe, ranging from the intergalactic and interstellar medium to planetary atmospheres.
\r\n\r\nPart I of the thesis consists of two independent investigations in which we study the effects of stellar feedback in high-redshift environments. The topic of Chapter 2 is the intergalactic medium (IGM) in the epoch just after the formation of the first stars in the Universe, but before the cosmic reionization was completed. This epoch is of great interest for the ongoing and future experiments aimed at observing the neutral IGM via the redshifted 21 cm line of hydrogen. We study the effects of resonant scattering of Lyman-\u03b1 photons produced by early stars on the structure of temperature fluctuations in the IGM. In Chapter 3, we use cosmological hydrodynamic simulations of galaxy evolution to study the effects of stellar feedback on the clumpy structure of star-forming galaxies at z ~ 2. Observations of high-redshift galaxies show that their morphology is often dominated by a few giant clumps of intense star formation, but the nature and the importance of these clumps for the evolution of their host galaxies are uncertain. We present a detailed analysis of the properties of giant clumps in a high-redshift simulated galaxy from the FIRE project.
\r\n\r\nPart II of the thesis is devoted to the effects of Raman scattering of stellar radiation in the atmospheres of extrasolar planets. Spectral signatures of Raman scattering imprinted in the geometric albedo spectrum of a gaseous planet carry information about the properties of the planet's atmosphere---its composition, temperature, and the radiation-penetration depth. In Chapter 5, we present the results of radiative transfer calculations including the treatment of Raman scattering for different types of planetary atmospheres and analyze the feasibility of detecting the spectral signatures of Raman scattering in nearby exoplanets. The structure and the intensity of Raman spectral features depends on both the atmospheric properties and the shape of the stellar spectrum irradiating the atmosphere. In Chapter 6, we analyze the diversity of Raman features in the geometric albedo spectra of planets hosted by different types of stars.
", "doi": "10.7907/Z9GM85CS", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:9906", "collection": "thesis", "collection_id": "9906", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08292016-174647631", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 8434177, "license": "other", "mime_type": "application/pdf", "url": "/9906/1/thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Low-Mass Stars and Their Companions", "author": [ { "family_name": "Montet", "given_name": "Benjamin Tyler", "orcid": "0000-0001-7516-8308", "clpid": "Montet-Benjamin-Tyler" } ], "thesis_advisor": [ { "family_name": "Johnson", "given_name": "John A.", "clpid": "Johnson-J-A" } ], "thesis_committee": [ { "family_name": "Hallinan", "given_name": "Gregg W.", "orcid": "0000-0002-7083-4049", "clpid": "Hallinan-G-W" }, { "family_name": "Johnson", "given_name": "John A.", "clpid": "Johnson-J-A" }, { "family_name": "Hopkins", "given_name": "Philip F.", "clpid": "Hopkins-P-F" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Knutson", "given_name": "Heather A.", "clpid": "Knutson-H-A" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "In this thesis, I present seven studies aimed towards better understanding the demographics and physical properties of M dwarfs and their companions. These studies focus in turn on planetary, brown dwarf, and stellar companions to M dwarfs.
\r\n\r\nI begin with an analysis of radial velocity and transit timing analyses of multi-transiting planetary systems, finding that if both signals are measured to sufficiently high precision the stellar and planetary masses can be measured to a high precision, eliminating a need for stellar models which may have systematic errors. I then combine long-term radial velocity monitoring and a direct imaging campaign to measure the occurrence rate of giant planets around M dwarfs. I find that 6.5 +/- 3.0% of M dwarfs host a Jupiter mass or larger planet within 20 AU, with a strong dependence on stellar metallicity.
\r\n\r\nI then present two papers analyzing the LHS 6343 system, which contains a widely separated M dwarf binary (AB). Star A hosts a transiting brown dwarf (LHS 6343 C) with a 12.7 day period. By combining radial velocity data with transit photometry, I am able to measure the mass and radius of the brown dwarf to 2% precision, the most precise measurement of a brown dwarf to date. I then analyze four secondary eclipses of the LHS 6343 AC system as observed by Spitzer in order to measure the luminosity of the brown dwarf in both Spitzer bandpasses. I find the brown dwarf is consistent with theoretical models of an 1100 K T dwarf at an age of 5 Gyr and empirical observations of field T5-6 dwarfs with temperatures of 1070 +/- 130 K. This is the first non-inflated brown dwarf with a measured mass, radius, and multi-band photometry, making it an ideal test of evolutionary models of field brown dwarfs.
\r\n\r\nNext, I present the results of an astrometric and radial velocity campaign to measure the orbit and masses of both stars in the GJ 3305 AB system, an M+M binary comoving with 51 Eridani, a more massive star with a directly imaged planetary companion. I compare the masses of both stars to largely untested theoretical models of young M dwarfs, finding that the models are consistent with the measured mass of star A but slightly overpredict the luminosity of star B.
\r\n\r\nIn the final two science chapters I focus on space-based transit surveys, present and future. First, I present the first catalog of statistically validated planets from the K2 mission, as well as updated stellar and planetary parameters for all systems with candidate planets in the first K2 field. The catalog includes K2-18b, a ``mini-Neptune'' planet that receives a stellar insolation consistent with the level that the Earth receives from the Sun, making it a useful comparison against planets of a similar size that are highly irradiated, such as GJ 1214 b. Finally, I present predictions for the WFIRST mission. While designed largely as a microlensing mission, I find it will be able to detect as many as 30,000 transiting planets towards the galactic bulge, providing information about how planet occurrence changes across the galaxy. These planets will be able to be confirmed largely through direct detection of their secondary eclipses. Moreover, I find that more than 50% of the planets it detects smaller than Neptune will be found around M dwarf hosts.
", "doi": "10.7907/Z9KW5D1R", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10294", "collection": "thesis", "collection_id": "10294", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06052017-232351957", "type": "thesis", "title": "Unveiling the Structure of Active Galactic Nuclei with Hard X-ray Spectroscopy", "author": [ { "family_name": "Balokovic", "given_name": "Mislav", "orcid": "0000-0003-0476-6647", "clpid": "Balokovic-Mislav" } ], "thesis_advisor": [ { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" } ], "thesis_committee": [ { "family_name": "Hopkins", "given_name": "Philip F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" }, { "family_name": "Hillenbrand", "given_name": "Lynne A.", "clpid": "Hillenbrand-L-A" }, { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" } ], "local_group": [ { "literal": "Space Radiation Laboratory" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Despite the long history of studies of active galactic nuclei (AGN), details of the structure of the accretion flow onto supermassive black holes are far from clear. Work presented in this thesis is directed at unveiling properties of AGN structure through broadband X-ray spectroscopy, with particular emphasis on the hard X-ray band (photon energies above 10 keV). With its unprecedented sensitivity in this energy band, the NuSTAR telescope provides the key observational diagnostics of the properties of the AGN X-ray source, the corona, and the surrounding gas in the accretion disk, the broad-line region, and the torus.
\r\n\r\nThe first study presented in this thesis focuses on measurements of the optical depth and the temperature of the plasma in the corona of an obscured AGN. Fitting theoretical spectral models for coronal emission to the NuSTAR data constrained these two basic physical parameters under the assumption of either spherical or disk-like geometry for the corona.
\r\n\r\n\r\nThe remainder of the thesis is dedicated to studies of the anisotropic obscuring structure broadly referred to as the torus. One of them is a case study of three heavily obscured AGN with spectra dominated by the X-ray light scattered and reprocessed in the torus, where it is possible to constrain one of the basic torus properties -- its globally averaged column density. The following study presents the calculation of a new spectral model for reprocessing of the intrinsic X-ray continuum within the torus. Its added flexibility compared to previously available models allows for both the average column density of the torus and its covering factor to be constrained from broadband X-ray spectra of a wide variety of AGN.
\r\n\r\n\r\nThe final part of the thesis in based on a large survey of the local obscured AGN population performed with NuSTAR. Spectral modeling of more than a hundred individual AGN, including both old and new spectral models, is presented. From analyses of the X-ray data for a large and representative AGN sample, for the first time, it is found that their tori preferentially have high covering factors and average column densities close to unity optical depth for Compton scattering.
\r\n", "doi": "10.7907/Z9WM1BG8", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:9604", "collection": "thesis", "collection_id": "9604", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03042016-144127692", "primary_object_url": { "basename": "Swarnima-Manohar-thesis-2016.pdf", "content": "final", "filesize": 8264476, "license": "other", "mime_type": "application/pdf", "url": "/9604/1/Swarnima-Manohar-thesis-2016.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Lurking in ULIRGs: Molecular Gas in local Merging Galaxies", "author": [ { "family_name": "Manohar", "given_name": "Swarnima", "orcid": "0000-0002-3506-566X", "clpid": "Manohar-Swarnima" } ], "thesis_advisor": [ { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" } ], "thesis_committee": [ { "family_name": "Sargent", "given_name": "Anneila Isabel", "orcid": "0000-0002-4633-5098", "clpid": "Sargent-A-I" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Hopkins", "given_name": "Philip F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" }, { "family_name": "Mawet", "given_name": "Dimitri", "orcid": "0000-0002-8895-4735", "clpid": "Mawet-D" }, { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Mergers and interacting galaxies are pivotal to the evolution of galaxies in the universe. They are the sites of prodigious star formation and key to understanding the starburst processes: the physical and chemical properties and the dynamics of the molecular gas. ULIRGs or Ultraluminous Infrared Galaxies are a result of many of these mergers. They host extreme starbursts, AGNs, and mergers. They are the perfect laboratory to probe the connection between starbursts, black hole accretion and mergers and to further our understanding of star formation and merging.
\r\n\r\nNGC 6240 and Arp 220 can be considered the founding members of this very active class of objects. They are in different stages of merging and hence are excellent case studies to further our understanding about the merging process. We have imaged the dense star-forming regions of these galaxies at sub-arcsec resolution with CARMA C and B Configurations (2\" and 0.5 - 0.8\"). Multi-band imaging allows excitation analysis of HCN, HCO+, HNC, and CS along with CO transitions to constrain the properties of the gas. Our dataset is unique in that we have observed these lines at similar resolutions and high sensitivity which can be used to derive line ratios of faint high excitation lines.
\r\n\r\nArp 220 has not had confirmed X-ray AGN detections for either nuclei. However, our observations indicate HCN/HNC ratios consistent with the chemistry of X-ray Dominated Regions (XDRs) -- a likely symptom of AGN. We calculated the molecular Hydrogen densities using each of the molecular species and conclude that assuming abundances of HNC and HCO+ similar to those in galactic sources are incorrect in the case of ULIRGs. The physical conditions in the dense molecular gas in ULIRGs alter these abundances. The derived H2 volume densities are ~ 5 x 104 cm-3 in both Arp 220 nuclei and ~ 104 cm-3 in NGC 6240.
", "doi": "10.7907/Z9T72FDK", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:9243", "collection": "thesis", "collection_id": "9243", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10232015-070212778", "type": "thesis", "title": "Deep Near-Infrared Spectroscopy of High-Redshift Galaxies: the Physical Growth of Passive Systems", "author": [ { "family_name": "Belli", "given_name": "Sirio", "orcid": "0000-0002-5615-6018", "clpid": "Belli-Sirio" } ], "thesis_advisor": [ { "family_name": "Ellis", "given_name": "Richard S.", "clpid": "Ellis-R-S" } ], "thesis_committee": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Steidel", "given_name": "Charles C.", "orcid": "0000-0002-4834-7260", "clpid": "Steidel-C-C" }, { "family_name": "Hopkins", "given_name": "Philip F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" }, { "family_name": "Hallinan", "given_name": "Gregg W.", "clpid": "Hallinan-G-W" }, { "family_name": "Ellis", "given_name": "Richard S.", "clpid": "Ellis-R-S" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "The assembly history of massive galaxies is one of the most important aspects of galaxy formation and evolution. Although we have a broad idea of what physical processes govern the early phases of galaxy evolution, there are still many open questions. In this thesis I demonstrate the crucial role that spectroscopy can play in a physical understanding of galaxy evolution. I present deep near-infrared spectroscopy for a sample of high-redshift galaxies, from which I derive important physical properties and their evolution with cosmic time. I take advantage of the recent arrival of efficient near-infrared detectors to target the rest-frame optical spectra of z > 1 galaxies, from which many physical quantities can be derived. After illustrating the applications of near-infrared deep spectroscopy with a study of star-forming galaxies, I focus on the evolution of massive quiescent systems.
\r\n\r\nMost of this thesis is based on two samples collected at the W. M. Keck Observatory that represent a significant step forward in the spectroscopic study of z > 1 quiescent galaxies. All previous spectroscopic samples at this redshift were either limited to a few objects, or much shallower in terms of depth. Our first sample is composed of 56 quiescent galaxies at 1 < z < 1.6 collected using the upgraded red arm of the Low Resolution Imaging Spectrometer (LRIS). The second consists of 24 deep spectra of 1.5 < z < 2.5 quiescent objects observed with the Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE). Together, these spectra span the critical epoch 1 < z < 2.5, where most of the red sequence is formed, and where the sizes of quiescent systems are observed to increase significantly.
\r\n\r\nWe measure stellar velocity dispersions and dynamical masses for the largest number of z > 1 quiescent galaxies to date. By assuming that the velocity dispersion of a massive galaxy does not change throughout its lifetime, as suggested by theoretical studies, we match galaxies in the local universe with their high-redshift progenitors. This allows us to derive the physical growth in mass and size experienced by individual systems, which represents a substantial advance over photometric inferences based on the overall galaxy population. We find a significant physical growth among quiescent galaxies over 0 < z < 2.5 and, by comparing the slope of growth in the mass-size plane dlogRe/dlogM\u2217 with the results of numerical simulations, we can constrain the physical process responsible for the evolution. Our results show that the slope of growth becomes steeper at higher redshifts, yet is broadly consistent with minor mergers being the main process by which individual objects evolve in mass and size.
\r\n\r\nBy fitting stellar population models to the observed spectroscopy and photometry we derive reliable ages and other stellar population properties. We show that the addition of the spectroscopic data helps break the degeneracy between age and dust extinction, and yields significantly more robust results compared to fitting models to the photometry alone. We detect a clear relation between size and age, where larger galaxies are younger. Therefore, over time the average size of the quiescent population will increase because of the contribution of large galaxies recently arrived to the red sequence. This effect, called progenitor bias, is different from the physical size growth discussed above, but represents another contribution to the observed difference between the typical sizes of low- and high-redshift quiescent galaxies. By reconstructing the evolution of the red sequence starting at z \u223c 1.25 and using our stellar population histories to infer the past behavior to z \u223c 2, we demonstrate that progenitor bias accounts for only half of the observed growth of the population. The remaining size evolution must be due to physical growth of individual systems, in agreement with our dynamical study.
\r\n\r\nFinally, we use the stellar population properties to explore the earliest periods which led to the formation of massive quiescent galaxies. We find tentative evidence for two channels of star formation quenching, which suggests the existence of two independent physical mechanisms. We also detect a mass downsizing, where more massive galaxies form at higher redshift, and then evolve passively. By analyzing in depth the star formation history of the brightest object at z > 2 in our sample, we are able to put constraints on the quenching timescale and on the properties of its progenitor.
\r\n\r\nA consistent picture emerges from our analyses: massive galaxies form at very early epochs, are quenched on short timescales, and then evolve passively. The evolution is passive in the sense that no new stars are formed, but significant mass and size growth is achieved by accreting smaller, gas-poor systems. At the same time the population of quiescent galaxies grows in number due to the quenching of larger star-forming galaxies. This picture is in agreement with other observational studies, such as measurements of the merger rate and analyses of galaxy evolution at fixed number density.
", "doi": "10.7907/Z9QN64NQ ", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:7966", "collection": "thesis", "collection_id": "7966", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09292013-182521898", "primary_object_url": { "basename": "stevenson_matthew_2014_thesis.pdf", "content": "final", "filesize": 13045735, "license": "other", "mime_type": "application/pdf", "url": "/7966/1/stevenson_matthew_2014_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Observational and Theoretical Advances in Cosmological Foreground Emission", "author": [ { "family_name": "Stevenson", "given_name": "Matthew Alan", "clpid": "Stevenson-Matthew-Alan" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Hillenbrand", "given_name": "Lynne A.", "clpid": "Hillenbrand-L-A" }, { "family_name": "Pearson", "given_name": "Timothy J.", "orcid": "0000-0001-5213-6231", "clpid": "Pearson-T-J" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Observational and theoretical work towards the separation of foreground emission from the cosmic microwave background is described. The bulk of this work is in the design, construction, and commissioning of the C-Band All-Sky Survey (C-BASS), an experiment to produce a template of the Milky Way Galaxy's polarized synchrotron emission. Theoretical work is the derivation of an analytical approximation to the emission spectrum of spinning dust grains.
\r\n\r\nThe performance of the C-BASS experiment is demonstrated through a preliminary, deep survey of the North Celestial Pole region. A comparison to multiwavelength data is performed, and the thermal and systematic noise properties of the experiment are explored. The systematic noise has been minimized through careful data processing algorithms, implemented both in the experiment's Field Programmable Gate Array (FPGA) based digital backend and in the data analysis pipeline. Detailed descriptions of these algorithms are presented.
\r\n\r\nThe analytical function of spinning dust emission is derived through the application of careful approximations, with each step tested against numerical calculations. This work is intended for use in the parameterized separation of cosmological foreground components and as a framework for interpreting and comparing the variety of anomalous microwave emission observations.
\r\n", "publication_date": "2014", "thesis_type": "phd", "thesis_year": "2014" }, { "id": "thesis:7966", "collection": "thesis", "collection_id": "7966", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09292013-182521898", "primary_object_url": { "basename": "stevenson_matthew_2014_thesis.pdf", "content": "final", "filesize": 13045735, "license": "other", "mime_type": "application/pdf", "url": "/7966/1/stevenson_matthew_2014_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Observational and Theoretical Advances in Cosmological Foreground Emission", "author": [ { "family_name": "Stevenson", "given_name": "Matthew Alan", "clpid": "Stevenson-Matthew-Alan" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Hillenbrand", "given_name": "Lynne A.", "clpid": "Hillenbrand-L-A" }, { "family_name": "Pearson", "given_name": "Timothy J.", "orcid": "0000-0001-5213-6231", "clpid": "Pearson-T-J" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Observational and theoretical work towards the separation of foreground emission from the cosmic microwave background is described. The bulk of this work is in the design, construction, and commissioning of the C-Band All-Sky Survey (C-BASS), an experiment to produce a template of the Milky Way Galaxy's polarized synchrotron emission. Theoretical work is the derivation of an analytical approximation to the emission spectrum of spinning dust grains.
\r\n\r\nThe performance of the C-BASS experiment is demonstrated through a preliminary, deep survey of the North Celestial Pole region. A comparison to multiwavelength data is performed, and the thermal and systematic noise properties of the experiment are explored. The systematic noise has been minimized through careful data processing algorithms, implemented both in the experiment's Field Programmable Gate Array (FPGA) based digital backend and in the data analysis pipeline. Detailed descriptions of these algorithms are presented.
\r\n\r\nThe analytical function of spinning dust emission is derived through the application of careful approximations, with each step tested against numerical calculations. This work is intended for use in the parameterized separation of cosmological foreground components and as a framework for interpreting and comparing the variety of anomalous microwave emission observations.
\r\n", "publication_date": "2014", "thesis_type": "phd", "thesis_year": "2014" }, { "id": "thesis:7842", "collection": "thesis", "collection_id": "7842", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06052013-104216835", "primary_object_url": { "basename": "czakon_thesis_2013.pdf", "content": "final", "filesize": 8414061, "license": "other", "mime_type": "application/pdf", "url": "/7842/1/czakon_thesis_2013.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Sunyaev-Zel\u2019dovich Observations Using Large-Format Millimeter Arrays", "author": [ { "family_name": "Czakon", "given_name": "Nicole Gisela", "clpid": "Czakon-Nicole-Gisela" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Benson", "given_name": "Andrew J.", "orcid": "0000-0001-5501-6008", "clpid": "Benson-A-J" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Zmuidzinas", "given_name": "Jonas", "clpid": "Zmuidzinas-J" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Galaxy clusters are the largest gravitationally bound objects in the observable universe, and they are formed from the largest perturbations of the primordial matter power spectrum. During initial cluster collapse, matter is accelerated to supersonic velocities, and the baryonic component is heated as it passes through accretion shocks. This process stabilizes when the pressure of the bound matter prevents further gravitational collapse. Galaxy clusters are useful cosmological probes, because their formation progressively freezes out at the epoch when dark energy begins to dominate the expansion and energy density of the universe. A diverse set of observables, from radio through X-ray wavelengths, are sourced from galaxy clusters, and this is useful for self-calibration. The distributions of these observables trace a cluster's dark matter halo, which represents more than 80% of the cluster's gravitational potential. One such observable is the Sunyaev-Zel'dovich effect (SZE), which results when the ionized intercluster medium blueshifts the cosmic microwave background via Compton scattering. Great technical advances in the last several decades have made regular observation of the SZE possible. Resolved SZE science, such as is explored in this analysis, has benefitted from the construction of large-format camera arrays consisting of highly sensitive millimeter-wave detectors, such as Bolocam. Bolocam is a submillimeter camera, sensitive to 140 GHz and 268 GHz radiation, located at one of the best observing sites in the world: the Caltech Submillimeter Observatory on Mauna Kea in Hawaii. Bolocam fielded 144 of the original spider web NTD bolometers used in an entire generation of ground-based, balloon-borne, and satellite-borne millimeter wave instrumention. Over approximately six years, our group at Caltech has developed a mature galaxy cluster observational program with Bolocam. This thesis describes the construction of the instrument's full cluster catalog: BOXSZ. Using this catalog, I have scaled the Bolocam SZE measurements with X-ray mass approximations in an effort to characterize the SZE signal as a viable mass probe for cosmology. This work has confirmed the SZE to be a low-scatter tracer of cluster mass. The analysis has also revealed how sensitive the SZE-mass scaling is to small biases in the adopted mass approximation. Future Bolocam analysis efforts are set on resolving these discrepancies by approximating cluster mass jointly with different observational probes.", "doi": "10.7907/SRVP-D536", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7784", "collection": "thesis", "collection_id": "7784", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302013-225100503", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 23016889, "license": "other", "mime_type": "application/pdf", "url": "/7784/1/thesis.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "The Relationship Between the Radio and Gamma-Ray Emission of Blazars", "author": [ { "family_name": "Max-Moerbeck Astudillo", "given_name": "Walter Kennerth", "clpid": "Max-Moerbeck-Astudillo-Walter-Kennerth" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" }, { "family_name": "Djorgovski", "given_name": "George", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-G" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Blazars are active galaxies with a jet closely oriented to our line of sight. They are powerful, variable emitters from radio to gamma-ray wavelengths. Although the general picture of synchrotron emission at low energies and inverse Compton at high energies is well established, important aspects of blazars are not well understood. In particular, the location of the gamma-ray emission region is not clearly established, with some theories favoring a location close to the central engine, while others place it at parsec scales in the radio jet.
\r\n\r\nWe developed a program to locate the gamma-ray emission site in blazars, through the study of correlated variations between their gamma-ray and radio-wave emission. Correlated variations are expected when there is a relation between emission processes at both bands, while delays tell us about the relative location of their energy generation zones. Monitoring at 15 GHz using the Owens Valley Radio Observatory 40 meter telescope started in mid-2007. The program monitors 1593 blazars twice per week, including all blazars detected by the Fermi Gamma-ray Space Telescope (Fermi) north of -20 degrees declination. This program complements the continuous monitoring of gamma-rays by Fermi.
\r\n\r\nThree year long gamma-ray light curves for bright Fermi blazars are cross-correlated with four years of radio monitoring. The significance of cross-correlation peaks is investigated using simulations that account for the uneven sampling and noise properties of the light curves, which are modeled as red-noise processes with a simple power-law power spectral density. We found that out of 86 sources with high quality data, only three show significant correlations (AO 0235+164, B2 2308+34 and PKS 1502+106). Additionally, we find a significant correlation for Mrk 421 when including the strong gamma-ray/radio flare of late 2012. In all four cases radio variations lag gamma-ray variations, suggesting that the gamma-ray emission originates upstream of the radio emission. For PKS 1502+106 we locate the gamma-ray emission site parsecs away from the central engine, thus disfavoring the model of Blandford and Levinson (1995), while other cases are inconclusive. These findings show that continuous monitoring over long time periods is required to understand the cross-correlation between gamma-ray and radio-wave variability in most blazars.
", "doi": "10.7907/ZX5X-V114", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7857", "collection": "thesis", "collection_id": "7857", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06062013-224902992", "primary_object_url": { "basename": "Levitan_PhD_Thesis.pdf", "content": "final", "filesize": 7130828, "license": "other", "mime_type": "application/pdf", "url": "/7857/1/Levitan_PhD_Thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Finding Needles in the Haystack: A Search for AM CVn Systems Using the Palomar Transient Factory", "author": [ { "family_name": "Levitan", "given_name": "David Benjamin", "clpid": "Levitan-David-Benjamin" } ], "thesis_advisor": [ { "family_name": "Prince", "given_name": "Thomas A.", "orcid": "0000-0002-8850-3627", "clpid": "Prince-T-A" } ], "thesis_committee": [ { "family_name": "Prince", "given_name": "Thomas A.", "orcid": "0000-0002-8850-3627", "clpid": "Prince-T-A" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "The AM CVn systems are a rare class of ultra-compact astrophysical binaries. With orbital periods of under an hour and as short as five minutes, they are among the closest known binary star systems and their evolution has direct relevance to the type Ia supernova rate and the white dwarf binary population. However, their faint and rare nature has made population studies of these systems difficult and several studies have found conflicting results.
\r\n\r\nI undertook a survey for AM CVn systems using the Palomar Transient Factory (PTF) astrophysical synoptic survey by exploiting the \"outbursts\" these systems undergo. Such events result in an increase in luminosity by a factor of up to two-hundred and are detectable in time-domain photometric data of AM CVn systems. My search resulted in the discovery of eight new systems, over 20% of the current known population. More importantly, this search was done in a systematic fashion, which allows for a population study properly accounting for biases.
\r\n\r\nApart from the discovery of new systems, I used the time-domain data from the PTF and other synoptic surveys to better understand the long-term behavior of these systems. This analysis of the photometric behavior of the majority of known AM CVn systems has shown changes in their behavior at longer time scales than have previously been observed. This has allowed me to find relationships between the outburst properties of an individual system and its orbital period.
\r\n\r\nEven more importantly, the systematically selected sample together with these properties have allowed me to conduct a population study of the AM CVn systems. I have shown that the latest published estimates of the AM CVn system population, a factor of fifty below theoretical estimates, are consistent with the sample of systems presented here. This is particularly noteworthy since my population study is most sensitive to a different orbital period regime than earlier surveys. This confirmation of the population density will allow the AM CVn systems population to be used in the study of other areas of astrophysics.
", "doi": "10.7907/MJJ0-7A67", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7286", "collection": "thesis", "collection_id": "7286", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11262012-212534634", "primary_object_url": { "basename": "DSRussell_Thesis_2012.pdf", "content": "final", "filesize": 16046459, "license": "other", "mime_type": "application/pdf", "url": "/7286/1/DSRussell_Thesis_2012.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Technology Advances for Radio Astronomy", "author": [ { "family_name": "Russell", "given_name": "Damon Stuart", "clpid": "Russell-Damon-Stuart" } ], "thesis_advisor": [ { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" } ], "thesis_committee": [ { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Gaier", "given_name": "Todd C.", "clpid": "Gaier-T-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The field of radio astronomy continues to provide fundamental contributions to the understanding of the evolution, and inner workings of, our universe. It has done so from its humble beginnings, where single antennas and receivers were used for observation, to today's focal plane arrays and interferometers. The number of receiving elements (pixels) in these instruments is quickly growing, currently approaching one hundred. For the instruments of tomorrow, the number of receiving elements will be in the thousands. Such instruments will enable researchers to peer deeper into the fabric of our universe and do so at faster survey speeds. They will provide enormous capability, both for unraveling today's mysteries as well as for the discovery of new phenomena.
\r\n \r\nAmong other challenges, producing the large numbers of low-noise amplifiers required for these instruments will be no easy task. The work described in this thesis advances the state of the art in three critical areas, technological advancements necessary for the future design and manufacturing of thousands of low-noise amplifiers. These areas being: the automated, cryogenic, probing of $\\diameter100$ mm indium phosphide wafers; a system for measuring the noise parameters of devices at cryogenic temperatures; and the development of low-noise, silicon germanium amplifiers for terahertz mixer receivers. The four chapters that comprise the body of this work detail the background, design, assembly, and testing involved in these contributions. Also included is a brief survey of noise parameters, the knowledge of which is fundamental to the design of low-noise amplifiers and the optimization of the system noise temperature for large, dense, interferometers.
", "doi": "10.7907/MW3P-2S22", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7286", "collection": "thesis", "collection_id": "7286", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11262012-212534634", "primary_object_url": { "basename": "DSRussell_Thesis_2012.pdf", "content": "final", "filesize": 16046459, "license": "other", "mime_type": "application/pdf", "url": "/7286/1/DSRussell_Thesis_2012.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Technology Advances for Radio Astronomy", "author": [ { "family_name": "Russell", "given_name": "Damon Stuart", "clpid": "Russell-Damon-Stuart" } ], "thesis_advisor": [ { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" } ], "thesis_committee": [ { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Gaier", "given_name": "Todd C.", "clpid": "Gaier-T-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The field of radio astronomy continues to provide fundamental contributions to the understanding of the evolution, and inner workings of, our universe. It has done so from its humble beginnings, where single antennas and receivers were used for observation, to today's focal plane arrays and interferometers. The number of receiving elements (pixels) in these instruments is quickly growing, currently approaching one hundred. For the instruments of tomorrow, the number of receiving elements will be in the thousands. Such instruments will enable researchers to peer deeper into the fabric of our universe and do so at faster survey speeds. They will provide enormous capability, both for unraveling today's mysteries as well as for the discovery of new phenomena.
\r\n \r\nAmong other challenges, producing the large numbers of low-noise amplifiers required for these instruments will be no easy task. The work described in this thesis advances the state of the art in three critical areas, technological advancements necessary for the future design and manufacturing of thousands of low-noise amplifiers. These areas being: the automated, cryogenic, probing of $\\diameter100$ mm indium phosphide wafers; a system for measuring the noise parameters of devices at cryogenic temperatures; and the development of low-noise, silicon germanium amplifiers for terahertz mixer receivers. The four chapters that comprise the body of this work detail the background, design, assembly, and testing involved in these contributions. Also included is a brief survey of noise parameters, the knowledge of which is fundamental to the design of low-noise amplifiers and the optimization of the system noise temperature for large, dense, interferometers.
", "doi": "10.7907/MW3P-2S22", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:6945", "collection": "thesis", "collection_id": "6945", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04182012-140409324", "primary_object_url": { "basename": "richards_joseph_l_2012_thesis.pdf", "content": "final", "filesize": 10085683, "license": "other", "mime_type": "application/pdf", "url": "/6945/1/richards_joseph_l_2012_thesis.pdf", "version": "v14.0.0" }, "type": "thesis", "title": "The Radio Variability of Gamma-Ray Blazars", "author": [ { "family_name": "Richards", "given_name": "Joseph Lee", "clpid": "Richards-Joseph-Lee" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Sargent", "given_name": "Wallace L. W.", "clpid": "Sargent-W-L-W" }, { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Since late 2007, we have regularly monitored over 1100 systematically selected blazars at 15 GHz using the Owens Valley Radio Observatory 40 m radio telescope. The number of sources in the program has grown to nearly 1600, including all the active galactic nuclei associated with Fermi Large Area Telescope (LAT) gamma-ray point source detections north of our declination limit of -20\u00b0. Here, we describe the first 42 months of this program, including the design and implementation of an automated data reduction pipeline and a MySQL database system for storing the reduced data and intermediate data products. Using the \"intrinsic modulation index,\" a maximum-likelihood method, we estimate the variability amplitudes for 1413 sources from their radio light curves and compare the properties of physically defined subpopulations of the sample. We find that, among our preselected sample, gamma-ray-loud blazars detected by the LAT are significantly more variable at 15 GHz, attributable to a difference in variability between the gamma-ray-loud and gamma-ray-quiet flat spectrum radio quasars. The BL Lacertae objects in the samples do not show this division in variability amplitudes. In the first two years of our program, a 3\u03c3-significant difference between variability amplitudes for sources at redshift z \u2265 1 and for sources at z < 1 was found. This difference is found no longer to be significant in the full 42-month data set, particularly after we apply an analysis method to account for the effect of cosmological time dilation. ", "doi": "10.7907/N69P-KG16", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6987", "collection": "thesis", "collection_id": "6987", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04272012-102231664", "type": "thesis", "title": "Topics in Large-Scale Structure", "author": [ { "family_name": "Krause", "given_name": "Anna Elisabeth", "clpid": "Krause-Anna-Elisabeth" } ], "thesis_advisor": [ { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" } ], "thesis_committee": [ { "family_name": "Sargent", "given_name": "Wallace L. W.", "clpid": "Sargent-W-L-W" }, { "family_name": "Benson", "given_name": "Andrew J.", "orcid": "0000-0001-5501-6008", "clpid": "Benson-A-J" }, { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" } ], "local_group": [ { "literal": "TAPIR" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "This thesis presents my personal survey of topics and methods in large-scale structure, covering a range of cosmological probes and analytical, numerical, and observational techniques.
\r\n\r\nChapters 2--4 present analytic calculations of systematic effects relevant for the interpretation of data from upcoming large-scale structure surveys: In chapter 2 we derive the relation between measured galaxy ellipticities and the cosmic shear power spectrum up to fourth order in the matter density field, accounting for multiple deflections along the light path, reduced shear, and magnification bias. In chapter 3 we develop a new third-order cosmic shear statistics, which separates shear three point correlation functions exactly into E- and B-mode correlations on a finite interval. Chapter 4 considers the effect of tidal galaxy alignments on the projected galaxy bispectrum, which are found to bias the inferred galaxy bias parameters.
\r\n\r\nChapter 5 focusses on the halo-occupation distribution formalism, which constrains the relation between galaxy luminosities and the masses of their host halos through clustering measurements. We extend this method to model the cross-correlation functions between a galaxy sample of interest and multiple tracer populations simultaneously. This technique improves the accuracy of clustering analyses for sparse galaxy populations, and we apply it to constrain the environment of $(NUV-r)$ selected green valley galaxy samples. These galaxy samples are constructed by matching the Sloan Digital Sky Survey with the latest Galaxy Evolution Explorer source catalog which provides NUV photometry. We present cross-correlation function measurements and determine the halo occupation distribution of these transitional galaxies using the multiple tracer technique.
\r\n\r\nIn chapter 6 we examine sources of scatter in scaling relations between galaxy cluster mass and thermal Sunyaev-Zeldovich (SZ) effect using cluster samples extracted from cosmological hydrodynamical simulations. This sample enables us to study for the first time the detailed evolution of merging clusters around the scaling relation for a cosmologically representative distribution of merger parameters. We find major mergers to cause an asymmetric scatter such that the inferred mass of merging systems is biased low. As the fraction of dynamically disturbed clusters increases with redshift, this analysis indicates that mergers cause a redshift-dependent bias in cluster mass scaling relations.
", "doi": "10.7907/9HX2-RW58", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6534", "collection": "thesis", "collection_id": "6534", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07022011-083421311", "type": "thesis", "title": "The SPIDER CMB Polarimeter", "author": [ { "family_name": "Trangsrud", "given_name": "Amy Ruth", "clpid": "Trangsrud-Amy-Ruth" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" } ], "thesis_committee": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" }, { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "SPIDER is a balloon-borne millimeter-wave telescope designed to study the polarization of the Cosmic Microwave Background (CMB). SPIDER will map 10% of the full sky with degree-scale beams to search for the distinctive inflationary gravitational wave signal on angular scales between 1 degree and 10 degrees, thereby probing the energy scale of inflation. In its first flight, SPIDER will field 2,400 antenna-coupled bolometers split between two bands centered at 93 GHz and 148 GHz. Slot antenna arrays, band defining microstrip filters and superconducting bolometers are all fabricated photolithographically on a shared silicon substrate. SPIDER's detectors are split amongst six monochromatic on-axis refractors in a shared helium-cooled cryostat. This thesis reviews the design of SPIDER and its antenna-coupled bolometers, and details the currently achieved performance of SPIDER's receivers.", "doi": "10.7907/83YV-A258", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6945", "collection": "thesis", "collection_id": "6945", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04182012-140409324", "primary_object_url": { "basename": "richards_joseph_l_2012_thesis.pdf", "content": "final", "filesize": 10085683, "license": "other", "mime_type": "application/pdf", "url": "/6945/1/richards_joseph_l_2012_thesis.pdf", "version": "v14.0.0" }, "type": "thesis", "title": "The Radio Variability of Gamma-Ray Blazars", "author": [ { "family_name": "Richards", "given_name": "Joseph Lee", "clpid": "Richards-Joseph-Lee" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Sargent", "given_name": "Wallace L. W.", "clpid": "Sargent-W-L-W" }, { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Since late 2007, we have regularly monitored over 1100 systematically selected blazars at 15 GHz using the Owens Valley Radio Observatory 40 m radio telescope. The number of sources in the program has grown to nearly 1600, including all the active galactic nuclei associated with Fermi Large Area Telescope (LAT) gamma-ray point source detections north of our declination limit of -20\u00b0. Here, we describe the first 42 months of this program, including the design and implementation of an automated data reduction pipeline and a MySQL database system for storing the reduced data and intermediate data products. Using the \"intrinsic modulation index,\" a maximum-likelihood method, we estimate the variability amplitudes for 1413 sources from their radio light curves and compare the properties of physically defined subpopulations of the sample. We find that, among our preselected sample, gamma-ray-loud blazars detected by the LAT are significantly more variable at 15 GHz, attributable to a difference in variability between the gamma-ray-loud and gamma-ray-quiet flat spectrum radio quasars. The BL Lacertae objects in the samples do not show this division in variability amplitudes. In the first two years of our program, a 3\u03c3-significant difference between variability amplitudes for sources at redshift z \u2265 1 and for sources at z < 1 was found. This difference is found no longer to be significant in the full 42-month data set, particularly after we apply an analysis method to account for the effect of cosmological time dilation. ", "doi": "10.7907/N69P-KG16", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:7136", "collection": "thesis", "collection_id": "7136", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06052012-140445171", "primary_object_url": { "basename": "tsg_thesis.pdf", "content": "final", "filesize": 9877751, "license": "other", "mime_type": "application/pdf", "url": "/7136/1/tsg_thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Topics in Galaxy Evolution: Early Star Formation and Quenching", "author": [ { "family_name": "Gon\u00e7alves", "given_name": "Thiago Signorini", "clpid": "Goncalves-Thiago-Signorini" } ], "thesis_advisor": [ { "family_name": "Martin", "given_name": "D. Christopher", "orcid": "0000-0002-8650-1644", "clpid": "Martin-D-Christopher" } ], "thesis_committee": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Martin", "given_name": "D. Christopher", "orcid": "0000-0002-8650-1644", "clpid": "Martin-D-Christopher" }, { "family_name": "Schiminovich", "given_name": "David", "clpid": "Schiminovich-D" }, { "family_name": "Benson", "given_name": "Andrew J.", "orcid": "0000-0001-5501-6008", "clpid": "Benson-A-J" }, { "family_name": "Johnson", "given_name": "John A.", "clpid": "Johnson-J-A" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "In this thesis, we present three projects designed to shed light on yet unanswered questions on galaxy formation and evolution. The first two concern a sample of UV-bright starburst galaxies in the local universe (z~0.2). These objects are remarkably similar to star-forming galaxies that were abundant at high redshifts (2<z<3) - the Lyman break galaxies - and can help explain the very distinctive properties observed at such epochs. Thus, these galaxies are denominated Lyman break analogs, or LBAs.
\r\n\r\nFirst, we describe a survey of kinematics of the nebular gas in such objects, and how that can help explain the formation process, including gas assembly, in these starbursts. We show strong evidence that the gas kinematics resemble those observed at high redshifts. However, by artificially manipulating our observations to mimic our objects at greater distances, we show how low resolution and signal-to-noise ratios can lead to erroneous conclusions, in particular when attempting to diagnose mergers as the origin of the starburst.
\r\n\r\nThen, we present results from a pilot survey to study the cold, molecular gas reservoir in such objects. Again, we show that the observed properties are analogous to those observed at high redshift, in particular with respect to baryonic gas fractions in the galaxy, higher than normally found in low-extinction objects in the local universe. Furthermore, we show how gas surface density and star-formation surface density follow the same relation as local galaxies, albeit at much higher values.
\r\n\r\nFinally, we discuss an observational project designed to measure the mass flux density from the blue sequence to the red sequence across the so-called green valley. We obtain the deepest spectra ever observed of green valley galaxies at intermediate redshifts (z~0.8) in order to measure spectral features from which we can measure the star formation histories of individual galaxies. We measure a mass flux ratio that is higher than observed in the local universe, indicating the red sequence was growing faster when the universe was half its present age than today.
", "doi": "10.7907/E5T6-AC13", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6987", "collection": "thesis", "collection_id": "6987", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04272012-102231664", "type": "thesis", "title": "Topics in Large-Scale Structure", "author": [ { "family_name": "Krause", "given_name": "Anna Elisabeth", "clpid": "Krause-Anna-Elisabeth" } ], "thesis_advisor": [ { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" } ], "thesis_committee": [ { "family_name": "Sargent", "given_name": "Wallace L. W.", "clpid": "Sargent-W-L-W" }, { "family_name": "Benson", "given_name": "Andrew J.", "orcid": "0000-0001-5501-6008", "clpid": "Benson-A-J" }, { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" } ], "local_group": [ { "literal": "TAPIR" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "This thesis presents my personal survey of topics and methods in large-scale structure, covering a range of cosmological probes and analytical, numerical, and observational techniques.
\r\n\r\nChapters 2--4 present analytic calculations of systematic effects relevant for the interpretation of data from upcoming large-scale structure surveys: In chapter 2 we derive the relation between measured galaxy ellipticities and the cosmic shear power spectrum up to fourth order in the matter density field, accounting for multiple deflections along the light path, reduced shear, and magnification bias. In chapter 3 we develop a new third-order cosmic shear statistics, which separates shear three point correlation functions exactly into E- and B-mode correlations on a finite interval. Chapter 4 considers the effect of tidal galaxy alignments on the projected galaxy bispectrum, which are found to bias the inferred galaxy bias parameters.
\r\n\r\nChapter 5 focusses on the halo-occupation distribution formalism, which constrains the relation between galaxy luminosities and the masses of their host halos through clustering measurements. We extend this method to model the cross-correlation functions between a galaxy sample of interest and multiple tracer populations simultaneously. This technique improves the accuracy of clustering analyses for sparse galaxy populations, and we apply it to constrain the environment of $(NUV-r)$ selected green valley galaxy samples. These galaxy samples are constructed by matching the Sloan Digital Sky Survey with the latest Galaxy Evolution Explorer source catalog which provides NUV photometry. We present cross-correlation function measurements and determine the halo occupation distribution of these transitional galaxies using the multiple tracer technique.
\r\n\r\nIn chapter 6 we examine sources of scatter in scaling relations between galaxy cluster mass and thermal Sunyaev-Zeldovich (SZ) effect using cluster samples extracted from cosmological hydrodynamical simulations. This sample enables us to study for the first time the detailed evolution of merging clusters around the scaling relation for a cosmologically representative distribution of merger parameters. We find major mergers to cause an asymmetric scatter such that the inferred mass of merging systems is biased low. As the fraction of dynamically disturbed clusters increases with redshift, this analysis indicates that mergers cause a redshift-dependent bias in cluster mass scaling relations.
", "doi": "10.7907/9HX2-RW58", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6395", "collection": "thesis", "collection_id": "6395", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05162011-094345225", "primary_object_url": { "basename": "Kasliwal_PhD_Thesis.pdf", "content": "final", "filesize": 7367790, "license": "other", "mime_type": "application/pdf", "url": "/6395/1/Kasliwal_PhD_Thesis.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Bridging the Gap: Elusive Explosions in the Local Universe", "author": [ { "family_name": "Kasliwal", "given_name": "Mansi Manoj", "orcid": "0000-0002-5619-4938", "clpid": "Kasliwal-Mansi-Manoj" } ], "thesis_advisor": [ { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" } ], "thesis_committee": [ { "family_name": "Ellis", "given_name": "Richard S.", "clpid": "Ellis-R-S" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Frail", "given_name": "Dale A.", "clpid": "Frail-D-A" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "For centuries, we have known that our dynamic universe is adorned by cosmic fireworks: energetic and ephemeral beacons of light from a single star that are a million (nova) to a billion (supernova) times brighter than our sun. However, it had been an age-old conundrum that the brightest nova is approximately 1000 times fainter than than the faintest supernova; why should nature leave such a wide \"gap\"?
\r\n\r\nIn search of an answer, I undertook three systematic surveys for my thesis. Since I was looking for transients fainter, faster and rarer than supernovae, I focused my search on galaxies in the local universe. We now have convincing evidence of multiple, distinct populations of rare transients bridging this \"gap\". Perhaps, we are witnessing new stellar physics --- shell detonations in ultra-compact white dwarf binaries, electron-capture supernovae, white dwarfs collapsing into neutron stars and birth of black-holes.
\r\n\r\nA small number of intensively followed-up discoveries of elusive transients sets the stage for population studies with the upcoming \"Large Synoptic Survey Telescope\". This effort works towards building a complete inventory of transients in the local universe (d < 200 Mpc). It better prepares us for the search for potential electromagnetic counterparts to events in the emerging fields of gravitational wave, neutrino and ultra high energy cosmic ray astronomy as these experiments are also limited to the local universe.
", "doi": "10.7907/EA7Q-WX87", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:6395", "collection": "thesis", "collection_id": "6395", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05162011-094345225", "primary_object_url": { "basename": "Kasliwal_PhD_Thesis.pdf", "content": "final", "filesize": 7367790, "license": "other", "mime_type": "application/pdf", "url": "/6395/1/Kasliwal_PhD_Thesis.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Bridging the Gap: Elusive Explosions in the Local Universe", "author": [ { "family_name": "Kasliwal", "given_name": "Mansi Manoj", "orcid": "0000-0002-5619-4938", "clpid": "Kasliwal-Mansi-Manoj" } ], "thesis_advisor": [ { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" } ], "thesis_committee": [ { "family_name": "Ellis", "given_name": "Richard S.", "clpid": "Ellis-R-S" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Frail", "given_name": "Dale A.", "clpid": "Frail-D-A" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "For centuries, we have known that our dynamic universe is adorned by cosmic fireworks: energetic and ephemeral beacons of light from a single star that are a million (nova) to a billion (supernova) times brighter than our sun. However, it had been an age-old conundrum that the brightest nova is approximately 1000 times fainter than than the faintest supernova; why should nature leave such a wide \"gap\"?
\r\n\r\nIn search of an answer, I undertook three systematic surveys for my thesis. Since I was looking for transients fainter, faster and rarer than supernovae, I focused my search on galaxies in the local universe. We now have convincing evidence of multiple, distinct populations of rare transients bridging this \"gap\". Perhaps, we are witnessing new stellar physics --- shell detonations in ultra-compact white dwarf binaries, electron-capture supernovae, white dwarfs collapsing into neutron stars and birth of black-holes.
\r\n\r\nA small number of intensively followed-up discoveries of elusive transients sets the stage for population studies with the upcoming \"Large Synoptic Survey Telescope\". This effort works towards building a complete inventory of transients in the local universe (d < 200 Mpc). It better prepares us for the search for potential electromagnetic counterparts to events in the emerging fields of gravitational wave, neutrino and ultra high energy cosmic ray astronomy as these experiments are also limited to the local universe.
", "doi": "10.7907/EA7Q-WX87", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:6404", "collection": "thesis", "collection_id": "6404", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05172011-165447651", "primary_object_url": { "basename": "yacine_thesis.pdf", "content": "final", "filesize": 3852550, "license": "other", "mime_type": "application/pdf", "url": "/6404/1/yacine_thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "A New Spin on Primordial Hydrogen Recombination and a Refined Model for Spinning Dust Radiation", "author": [ { "family_name": "Ali-Haimoud", "given_name": "Yacine", "clpid": "Ali-Haimoud-Yacine" } ], "thesis_advisor": [ { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" } ], "thesis_committee": [ { "family_name": "Kamionkowski", "given_name": "Marc P.", "orcid": "0000-0001-7018-2055", "clpid": "Kamionkowski-M-P" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" }, { "family_name": "Hirata", "given_name": "Christopher M.", "orcid": "0000-0002-2951-4932", "clpid": "Hirata-C-M" } ], "local_group": [ { "literal": "TAPIR" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "This thesis describes theoretical calculations in two subjects: the primordial recombination of the electron-proton plasma about 400,000 years after the Big Bang and electric dipole radiation from spinning dust grains in the present-day interstellar medium.
\r\n\r\nPrimordial hydrogen recombination has recently been the subject of a renewed attention because of the impact of its theoretical uncertainties on predicted cosmic microwave background (CMB) anisotropy power spectra. The physics of the primordial recombination problem can be divided into two qualitatively different aspects. On the one hand, a detailed treatment of the non-thermal radiation field in the optically thick Lyman lines is required for an accurate recombination history near the peak of the visibility function. On the other hand, stimulated recombinations and out-of equilibrium effects are important at late times and a multilevel calculation is required to correctly compute the low-redshift end of the ionization history. Another facet of the problem is the requirement of computational efficiency, as a large number of recombination histories must be evaluated in Markov chains when analyzing CMB data. In this thesis, an effective multilevel atom method is presented, that speeds up multilevel atom computations by more than 5 orders of magnitude. The impact of previously ignored radiative transfer effects is quantified, and explicitly shown to be negligible. Finally, the numerical implementation of a fast and highly accurate primordial recombination code partly written by the author is described.
\r\n\r\nThe second part of this thesis is devoted to one of the potential galactic foregrounds for CMB experiments: the rotational emission from small dust grains. The rotational state of dust grains is described, first classically, and assuming that grains are rotating about their axis of greatest inertia. This assumption is then lifted, and a quantum-mechanical calculation is presented for disk-like grains with a randomized nutation state. In both cases, the probability distribution for the total grain angular momentum is computed with a Fokker-Planck equation, and the resulting emissivity is evaluated, as a function of environmental parameters. These computations are implemented in a public code written by the author.
", "doi": "10.7907/QMFZ-0C90", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:5295", "collection": "thesis", "collection_id": "5295", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10122009-094525715", "type": "thesis", "title": "Instrumentation for Wide Bandwidth Radio Astronomy", "author": [ { "family_name": "Jones", "given_name": "Glenn Evans", "clpid": "Jones-Glenn-Evans" } ], "thesis_advisor": [ { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "orcid": "0000-0003-3003-7042", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Kuiper", "given_name": "Thomas B. H.", "clpid": "Kuiper-T-B-H" }, { "family_name": "Jarnot", "given_name": "Robert F.", "clpid": "Jarnot-R-F" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Centimeter wavelength radio astronomy spans approximately two decades in frequency, from roughly 500 MHz to 50 GHz. In contrast, radio astronomy instruments have traditionally been limited to at most octave bandwidths, necessitating multiple instruments on a given telescope to cover a large fraction of the spectrum. This paradigm is infeasible for the next generation of telescopes, which will likely consist of hundreds to thousands of small dishes combined together in an array, because each receiver must be replicated for each element in the array. Therefore, wide bandwidth instrumentation must be developed for radio astronomy.
\r\n\r\nThis thesis presents a novel radio telescope with excellent system noise temperature and reasonable efficiency across an instantaneous fractional bandwidth greater than 4:1; amongst the widest ever demonstrated. This instrument illustrates that extremely wide bandwidth instruments are feasible, even in the presence of terrestrial interference. To make use of the enormous instantaneous bandwidth, a flexible, high performance, and cost effective digital signal processing system is also presented. Theory, design, and measurements of special purpose digital spectrometers built to minimize the effects of terrestrial interference are included.
\r\n\r\nAside from the practical advantages offered by wide bandwidth instrumentation, new scientific applications are also made possible. A special purpose system for performing detailed studies of giant radio pulses from rotating neutron stars (pulsars) is presented, along with demonstrations including some of the largest fractional bandwidth observations of these pulses made to date. This system includes a sensitive trigger which corrects for the dispersive effects of the interstellar medium in real time and a deep capture buffer optimized for observing repetitive transient phenomena. Measurements made using the trigger system at Arecibo Observatory are also presented to demonstrate the portability of the instrument.
", "doi": "10.7907/BMZR-P813", "publication_date": "2010", "thesis_type": "phd", "thesis_year": "2010" }, { "id": "thesis:5295", "collection": "thesis", "collection_id": "5295", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10122009-094525715", "type": "thesis", "title": "Instrumentation for Wide Bandwidth Radio Astronomy", "author": [ { "family_name": "Jones", "given_name": "Glenn Evans", "clpid": "Jones-Glenn-Evans" } ], "thesis_advisor": [ { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "orcid": "0000-0003-3003-7042", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Kuiper", "given_name": "Thomas B. H.", "clpid": "Kuiper-T-B-H" }, { "family_name": "Jarnot", "given_name": "Robert F.", "clpid": "Jarnot-R-F" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Centimeter wavelength radio astronomy spans approximately two decades in frequency, from roughly 500 MHz to 50 GHz. In contrast, radio astronomy instruments have traditionally been limited to at most octave bandwidths, necessitating multiple instruments on a given telescope to cover a large fraction of the spectrum. This paradigm is infeasible for the next generation of telescopes, which will likely consist of hundreds to thousands of small dishes combined together in an array, because each receiver must be replicated for each element in the array. Therefore, wide bandwidth instrumentation must be developed for radio astronomy.
\r\n\r\nThis thesis presents a novel radio telescope with excellent system noise temperature and reasonable efficiency across an instantaneous fractional bandwidth greater than 4:1; amongst the widest ever demonstrated. This instrument illustrates that extremely wide bandwidth instruments are feasible, even in the presence of terrestrial interference. To make use of the enormous instantaneous bandwidth, a flexible, high performance, and cost effective digital signal processing system is also presented. Theory, design, and measurements of special purpose digital spectrometers built to minimize the effects of terrestrial interference are included.
\r\n\r\nAside from the practical advantages offered by wide bandwidth instrumentation, new scientific applications are also made possible. A special purpose system for performing detailed studies of giant radio pulses from rotating neutron stars (pulsars) is presented, along with demonstrations including some of the largest fractional bandwidth observations of these pulses made to date. This system includes a sensitive trigger which corrects for the dispersive effects of the interstellar medium in real time and a deep capture buffer optimized for observing repetitive transient phenomena. Measurements made using the trigger system at Arecibo Observatory are also presented to demonstrate the portability of the instrument.
", "doi": "10.7907/BMZR-P813", "publication_date": "2010", "thesis_type": "phd", "thesis_year": "2010" }, { "id": "thesis:3016", "collection": "thesis", "collection_id": "3016", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08042008-124002", "type": "thesis", "title": "The Kiloparsec-Scale Structure and Kinematics of High-Redshift Star-Forming Galaxies", "author": [ { "family_name": "Law", "given_name": "David Richard", "orcid": "0000-0002-9402-186X", "clpid": "Law-David-Richard-Astrophysics" } ], "thesis_advisor": [ { "family_name": "Steidel", "given_name": "Charles C.", "orcid": "0000-0002-4834-7260", "clpid": "Steidel-C-C" } ], "thesis_committee": [ { "family_name": "Ellis", "given_name": "Richard S.", "clpid": "Ellis-R-S" }, { "family_name": "Benson", "given_name": "Andrew J.", "orcid": "0000-0001-5501-6008", "clpid": "Benson-A-J" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Steidel", "given_name": "Charles C.", "orcid": "0000-0002-4834-7260", "clpid": "Steidel-C-C" }, { "family_name": "Sargent", "given_name": "Wallace L. W.", "clpid": "Sargent-W-L-W" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "We study the spatially resolved properties of star-forming galaxies at redshift z ~ 2 - 3 on scales ~ 1 kpc using a combination of morphological and kinematic analyses in an effort to characterize the major mechanisms of galaxy formation in the young universe. Using a sample of 216 galaxies which have been spectroscopically confirmed to lie between redshifts z = 1.8 - 3.4 in the GOODS-N field we demonstrate that rest-UV morphology (as seen by the Hubble Space Telescope) is statistically uncorrelated with physical properties such as star formation rate and is therefore unable to support the hypothesis that the prevalence of irregular morphologies indicates a high major merger fraction. Further, we present a sample of 13 galaxies observed with the OSIRIS integral field spectrograph and the Keck laser-guide star adaptive optics system which demonstrate the prevalence of high velocity dispersions ~ 80 km/s and generally little in the way of spatially resolved velocity gradients, inconsistent with favored rotating disk models. We discuss the implications of these results for galaxy formation models, including gas accretion via cold flows and gravitational instability of early gas-rich galactic disks. There is some evidence for a trend towards stronger rotational signatures in galaxies with more massive stellar populations. ", "doi": "10.7907/QNV4-9V14", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:4187", "collection": "thesis", "collection_id": "4187", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10192008-143041", "primary_object_url": { "basename": "elina_brobeck_thesis.pdf", "content": "final", "filesize": 6632848, "license": "other", "mime_type": "application/pdf", "url": "/4187/1/elina_brobeck_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Measurement of Ultra-High Energy Cosmic Rays with CHICOS", "author": [ { "family_name": "Brobeck", "given_name": "Elina", "clpid": "Brobeck-Elina" } ], "thesis_advisor": [ { "family_name": "McKeown", "given_name": "Robert D.", "clpid": "McKeown-R-D" } ], "thesis_committee": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" }, { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" }, { "family_name": "Kamionkowski", "given_name": "Marc P.", "orcid": "0000-0001-7018-2055", "clpid": "Kamionkowski-M-P" }, { "family_name": "McKeown", "given_name": "Robert D.", "clpid": "McKeown-R-D" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "The California HIgh school Cosmic ray ObServatory (CHICOS) is a ground-based scintillator array designed to measure the extended air showers of ultra-high energy cosmic rays. The goal of the project is to gain insight into the origin of ultra-high energy cosmic rays by measuring the energy spectrum and the distribution of arrival directions.
\r\n\r\nThe CHICOS array has been in operation since 2003. It consists of 77 pairs of scintillator dectectors deployed at schools in the San Fernando and San Gabriel valleys near Los Angeles, and is designed to observe cosmic ray air showers at energies of 10^18 eV and above. In addition, the Chiquita subarray is designed to observe smaller showers in the energy range of 1016 - 1019 eV.
\r\n\r\nWe present new descriptions of the air shower lateral distribution function and time distribution function, which have been derived from AIRES-generated simulated air showers. The new functions are specific to the CHICOS altitude and allow for a maximum likelihood shower reconstruction method, which is more appropriate to the CHICOS data than the \u03c72 minimization method. We present several analyses of the accuracy of the reconstruction software in the energy ranges available to the Chiquita and CHICOS arrays.
\r\n\r\nThe energy spectrum between 1017 eV and 1019 eV has been measured by the Chiquita subarray. At the lowest energy range, it is found to agree with previous measurements, while the measured flux falls below previous experiments for energies greater than approximately 1017.5 eV. The CHICOS energy spectrum above 1018.4 eV is found to agree with previous results published by AGASA. However, we do not observe the cutoff in the spectrum at 1020 eV reported more recently by the Auger and HiRes Collaborations.
\r\n\r\nA correlation analysis between CHICOS data and nearby active galactic nuclei (AGN) was performed. No excess of cosmic rays was observed in the vicinity of nearby AGN. The maximum correlation was observed for cosmic ray events with E > 1020 eV and for AGN with z < 0.009, with Pchance = 21%. This is consistent with random correlations from an isotropic distribution, a result also found by HiRes, but in disagreement with Auger.
\r\n", "doi": "10.7907/9YH6-N064", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:4187", "collection": "thesis", "collection_id": "4187", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10192008-143041", "primary_object_url": { "basename": "elina_brobeck_thesis.pdf", "content": "final", "filesize": 6632848, "license": "other", "mime_type": "application/pdf", "url": "/4187/1/elina_brobeck_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Measurement of Ultra-High Energy Cosmic Rays with CHICOS", "author": [ { "family_name": "Brobeck", "given_name": "Elina", "clpid": "Brobeck-Elina" } ], "thesis_advisor": [ { "family_name": "McKeown", "given_name": "Robert D.", "clpid": "McKeown-R-D" } ], "thesis_committee": [ { "family_name": "Stone", "given_name": "Edward C.", "orcid": "0000-0002-2010-5462", "clpid": "Stone-E-C" }, { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" }, { "family_name": "Kamionkowski", "given_name": "Marc P.", "orcid": "0000-0001-7018-2055", "clpid": "Kamionkowski-M-P" }, { "family_name": "McKeown", "given_name": "Robert D.", "clpid": "McKeown-R-D" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "The California HIgh school Cosmic ray ObServatory (CHICOS) is a ground-based scintillator array designed to measure the extended air showers of ultra-high energy cosmic rays. The goal of the project is to gain insight into the origin of ultra-high energy cosmic rays by measuring the energy spectrum and the distribution of arrival directions.
\r\n\r\nThe CHICOS array has been in operation since 2003. It consists of 77 pairs of scintillator dectectors deployed at schools in the San Fernando and San Gabriel valleys near Los Angeles, and is designed to observe cosmic ray air showers at energies of 10^18 eV and above. In addition, the Chiquita subarray is designed to observe smaller showers in the energy range of 1016 - 1019 eV.
\r\n\r\nWe present new descriptions of the air shower lateral distribution function and time distribution function, which have been derived from AIRES-generated simulated air showers. The new functions are specific to the CHICOS altitude and allow for a maximum likelihood shower reconstruction method, which is more appropriate to the CHICOS data than the \u03c72 minimization method. We present several analyses of the accuracy of the reconstruction software in the energy ranges available to the Chiquita and CHICOS arrays.
\r\n\r\nThe energy spectrum between 1017 eV and 1019 eV has been measured by the Chiquita subarray. At the lowest energy range, it is found to agree with previous measurements, while the measured flux falls below previous experiments for energies greater than approximately 1017.5 eV. The CHICOS energy spectrum above 1018.4 eV is found to agree with previous results published by AGASA. However, we do not observe the cutoff in the spectrum at 1020 eV reported more recently by the Auger and HiRes Collaborations.
\r\n\r\nA correlation analysis between CHICOS data and nearby active galactic nuclei (AGN) was performed. No excess of cosmic rays was observed in the vicinity of nearby AGN. The maximum correlation was observed for cosmic ray events with E > 1020 eV and for AGN with z < 0.009, with Pchance = 21%. This is consistent with random correlations from an isotropic distribution, a result also found by HiRes, but in disagreement with Auger.
\r\n", "doi": "10.7907/9YH6-N064", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:3016", "collection": "thesis", "collection_id": "3016", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08042008-124002", "type": "thesis", "title": "The Kiloparsec-Scale Structure and Kinematics of High-Redshift Star-Forming Galaxies", "author": [ { "family_name": "Law", "given_name": "David Richard", "orcid": "0000-0002-9402-186X", "clpid": "Law-David-Richard-Astrophysics" } ], "thesis_advisor": [ { "family_name": "Steidel", "given_name": "Charles C.", "orcid": "0000-0002-4834-7260", "clpid": "Steidel-C-C" } ], "thesis_committee": [ { "family_name": "Ellis", "given_name": "Richard S.", "clpid": "Ellis-R-S" }, { "family_name": "Benson", "given_name": "Andrew J.", "orcid": "0000-0001-5501-6008", "clpid": "Benson-A-J" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Steidel", "given_name": "Charles C.", "orcid": "0000-0002-4834-7260", "clpid": "Steidel-C-C" }, { "family_name": "Sargent", "given_name": "Wallace L. W.", "clpid": "Sargent-W-L-W" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "We study the spatially resolved properties of star-forming galaxies at redshift z ~ 2 - 3 on scales ~ 1 kpc using a combination of morphological and kinematic analyses in an effort to characterize the major mechanisms of galaxy formation in the young universe. Using a sample of 216 galaxies which have been spectroscopically confirmed to lie between redshifts z = 1.8 - 3.4 in the GOODS-N field we demonstrate that rest-UV morphology (as seen by the Hubble Space Telescope) is statistically uncorrelated with physical properties such as star formation rate and is therefore unable to support the hypothesis that the prevalence of irregular morphologies indicates a high major merger fraction. Further, we present a sample of 13 galaxies observed with the OSIRIS integral field spectrograph and the Keck laser-guide star adaptive optics system which demonstrate the prevalence of high velocity dispersions ~ 80 km/s and generally little in the way of spatially resolved velocity gradients, inconsistent with favored rotating disk models. We discuss the implications of these results for galaxy formation models, including gas accretion via cold flows and gravitational instability of early gas-rich galactic disks. There is some evidence for a trend towards stronger rotational signatures in galaxies with more massive stellar populations. ", "doi": "10.7907/QNV4-9V14", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:907", "collection": "thesis", "collection_id": "907", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03092006-120454", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 4141403, "license": "other", "mime_type": "application/pdf", "url": "/907/1/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Mass Assembly History of Field Galaxies", "author": [ { "family_name": "Bundy", "given_name": "Kevin A.", "orcid": "0000-0001-9742-3138", "clpid": "Bundy-Kevin-A" } ], "thesis_advisor": [ { "family_name": "Ellis", "given_name": "Richard S.", "clpid": "Ellis-R-S" } ], "thesis_committee": [ { "family_name": "Sari", "given_name": "Re'em", "orcid": "0000-0002-1084-3656", "clpid": "Sari-R" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Steidel", "given_name": "Charles C.", "orcid": "0000-0002-4834-7260", "clpid": "Steidel-C-C" }, { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" }, { "family_name": "Ellis", "given_name": "Richard S.", "clpid": "Ellis-R-S" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "The work presented in this thesis utilizes the combination of near-IR photometry and spectroscopic redshifts to estimate the stellar masses of distant field galaxies in order to characterize their assembly history since z~1. The primary data set for this analysis comes from an extensive near-IR survey conducted at Palomar Observatory that includes over 12,000 galaxies detected in the Ks-band with DEEP2 spectroscopic redshifts in the range 0.2<z<1.5. Utilizing stellar masses estimated for this sample, little evolution is observed in the galaxy stellar mass function since z~1, indicating that the stellar content of intermediate to high-mass galaxies has largely assembled by this epoch. Significant evolution since z~1 in the characteristics of the galaxy population does take place, however. As a function of time, red early-types--already established at the highest masses at z~1--increase in abundance as star formation shifts to late-type galaxies with lower masses. This pattern is interpreted in the context of \"downsizing,\" and a new mechanism is proposed that is capable of quenching star formation in massive galaxies and driving their morphological transformation into systems with spheroidal configurations.
\r\n\r\nNew diagnostics are introduced to quantify this downsizing behavior including the quenching mass, M_Q, which traces the stellar mass scale above which star formation in galaxies is suppressed. M_Q decreases by a factor of ~5 after z~1, indicating that the quenching mechanism responsible for downsizing becomes more efficient in galaxies with lower masses as a function of time. This evolution is analyzed as a function of environmental density, and no environmental dependence is observed except in the most extreme environments, where downsizing appears to be slightly accelerated in high density regions. This weak environmental dependence suggests that the quenching mechanism for most galaxies is primarily driven by internal processes. The nature of the quenching mechanism is discussed in the context of CDM galaxy formation models, and additional motivation for this comparison is also presented in a direct study of the near-IR merger rate and an analysis of the relationship between stellar mass and dark matter in disk galaxies.
", "doi": "10.7907/3QVQ-FH17", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:1972", "collection": "thesis", "collection_id": "1972", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05232005-160004", "primary_object_url": { "basename": "main.pdf", "content": "final", "filesize": 1173634, "license": "other", "mime_type": "application/pdf", "url": "/1972/1/main.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "To the Horizon and Beyond:Weak Lensing of the CMB and Binary Inspirals into Horizonless Objects", "author": [ { "family_name": "Kesden", "given_name": "Michael Henry", "orcid": "0000-0002-5987-1471", "clpid": "Kesden-Michael-Henry" } ], "thesis_advisor": [ { "family_name": "Kamionkowski", "given_name": "Marc P.", "orcid": "0000-0001-7018-2055", "clpid": "Kamionkowski-M-P" } ], "thesis_committee": [ { "family_name": "Kamionkowski", "given_name": "Marc P.", "orcid": "0000-0001-7018-2055", "clpid": "Kamionkowski-M-P" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Wise", "given_name": "Mark B.", "orcid": "0000-0002-9125-801X", "clpid": "Wise-M-B" } ], "local_group": [ { "literal": "TAPIR" }, { "literal": "div_pma" } ], "abstract": "This thesis examines two predictions of general relativity: weak lensing and gravitational waves. The cosmic microwave background (CMB) is gravitationally lensed by the large-scale structure between the observer and the last-scattering surface. This weak lensing induces non-Gaussian correlations that can be used to construct estimators for the deflection field. The error and bias of these estimators are derived and used to analyze the viability of lensing reconstruction for future CMB experiments.
\r\n\r\nWeak lensing also affects the one-point probability distribution function of the CMB. The skewness and kurtosis induced by lensing and the Sunayev-Zel'dovich (SZ) effect are calculated as functions of the angular smoothing scale of the map. While these functions offer the advantage of easy computability, only the skewness from lensing-SZ correlations can potentially be detected, even in the limit of the largest amplitude fluctuations allowed by observation.
\r\n\r\nLensing estimators are also essential to constrain inflation, the favored explanation for large-scale isotropy and the origin of primordial perturbations. B-mode polarization is considered to be a \"smoking-gun\" signature of inflation, and lensing estimators can be used to recover primordial B-modes from lensing-induced contamination. The ability of future CMB experiments to constrain inflation is assessed as functions of survey size and instrumental sensitivity.
\r\n\r\nA final application of lensing estimators is to constrain a possible cutoff in primordial density perturbations on near-horizon scales. The paucity of independent modes on such scales limits the statistical certainty of such a constraint. Measurements of the deflection field can be used to constrain at the 3-sigma level the existence of a cutoff large enough to account for current CMB observations.
\r\n\r\nA final chapter of this thesis considers an independent topic: the gravitational-wave (GW) signature of a binary inspiral into a horizonless object. If the supermassive objects at galactic centers lack the horizons of traditional black holes, inspiraling objects could emit GWs after passing within their surfaces. The GWs produced by such an inspiral are calculated, revealing distinctive features potentially observable by future GW observatories.
", "doi": "10.7907/BQMR-4C14", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:1716", "collection": "thesis", "collection_id": "1716", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05102005-102535", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 29088900, "license": "other", "mime_type": "application/pdf", "url": "/1716/2/thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "A Measurement of the Temperature and Polarization Anisotropies in the Cosmic Microwave Background Radiation", "author": [ { "family_name": "Jones", "given_name": "William Claude", "orcid": "0000-0002-3636-1241", "clpid": "Jones-William-Claude" } ], "thesis_advisor": [ { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" } ], "thesis_committee": [ { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Kamionkowski", "given_name": "Marc P.", "orcid": "0000-0001-7018-2055", "clpid": "Kamionkowski-M-P" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "We describe the design and performance of the Boomerang experiment, and report on measurements of the temperature and polarization anisotropies of the Cosmic Microwave Background (CMB) obtained during the January 2003 flight of Boomerang (B2K). To enable these studies, we have developed a bolometric detector which is intrinsically sensitive to linear polarization. The receiver consists of a pair of co-located silicon nitride micromesh absorbers which couple anisotropically to linearly polarized radiation through a corrugated waveguide structure. This system allows simultaneous background limited measurements of the Stokes I and Q parameters over ~30% bandwidths at frequencies from ~60 to 400 GHz.
\r\n\r\nThe science results reported here are derived from 195 hours of observation with four 145 GHz Polarization Sensitive Bolometer (PSB) pairs. The data include 75 hours of observations distributed over 1.8% of the sky with an additional 120 hours concentrated on the central portion of the field, itself representing 0.22% of the full sky. The B2K data improve significantly on existing measurements of the CMB temperature power spectrum at angular scales of 500 < l < 1100. In addition we have measured a spectrum of curl-free polarization anisotropies which, in the context of the most simple adiabatic inflationary models, are consistent with the predictions of the currently favored LCDM cosmology
", "doi": "10.7907/88BF-1W23", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:1716", "collection": "thesis", "collection_id": "1716", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05102005-102535", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 29088900, "license": "other", "mime_type": "application/pdf", "url": "/1716/2/thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "A Measurement of the Temperature and Polarization Anisotropies in the Cosmic Microwave Background Radiation", "author": [ { "family_name": "Jones", "given_name": "William Claude", "orcid": "0000-0002-3636-1241", "clpid": "Jones-William-Claude" } ], "thesis_advisor": [ { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" } ], "thesis_committee": [ { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Kamionkowski", "given_name": "Marc P.", "orcid": "0000-0001-7018-2055", "clpid": "Kamionkowski-M-P" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "We describe the design and performance of the Boomerang experiment, and report on measurements of the temperature and polarization anisotropies of the Cosmic Microwave Background (CMB) obtained during the January 2003 flight of Boomerang (B2K). To enable these studies, we have developed a bolometric detector which is intrinsically sensitive to linear polarization. The receiver consists of a pair of co-located silicon nitride micromesh absorbers which couple anisotropically to linearly polarized radiation through a corrugated waveguide structure. This system allows simultaneous background limited measurements of the Stokes I and Q parameters over ~30% bandwidths at frequencies from ~60 to 400 GHz.
\r\n\r\nThe science results reported here are derived from 195 hours of observation with four 145 GHz Polarization Sensitive Bolometer (PSB) pairs. The data include 75 hours of observations distributed over 1.8% of the sky with an additional 120 hours concentrated on the central portion of the field, itself representing 0.22% of the full sky. The B2K data improve significantly on existing measurements of the CMB temperature power spectrum at angular scales of 500 < l < 1100. In addition we have measured a spectrum of curl-free polarization anisotropies which, in the context of the most simple adiabatic inflationary models, are consistent with the predictions of the currently favored LCDM cosmology
", "doi": "10.7907/88BF-1W23", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:2085", "collection": "thesis", "collection_id": "2085", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05262004-231543", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 2232600, "license": "other", "mime_type": "application/pdf", "url": "/2085/1/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Radiative Transfer in Accreting Environments", "author": [ { "family_name": "Broderick", "given_name": "Avery Earl", "orcid": "0000-0002-3351-760X", "clpid": "Broderick-Avery-Earl" } ], "thesis_advisor": [ { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" } ], "thesis_committee": [ { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Thorne", "given_name": "Kip S.", "clpid": "Thorne-K-S" }, { "family_name": "Kamionkowski", "given_name": "Marc P.", "clpid": "Kamionkowski-M-P" } ], "local_group": [ { "literal": "TAPIR" }, { "literal": "div_pma" } ], "abstract": "Accretion onto compact objects plays a central role in high-energy astrophysics. The process of accretion can substantially affect the magnetic field strength and geometry (e.g, via the magneto-rotational instability or dynamo processes) and the accreting plasma density. The presence of the compact object itself can significantly affect the character and structure of the accreting plasma as well as its emission. This is especially true, in the case of an accreting black hole, when a significant fraction of the emission originates or passes near the horizon. To address this, we develop a manifestly covariant magnetoionic theory, capable of tracing rays in the geometric optics approximation through a magnetized plasma in a general relativistic environment. This is discussed for both the cold and warm, ion and pair plasmas. We also address the problem of performing polarized radiative transfer covariantly in these environments, considering in particular the anisotropic nature of magnetized plasmas, the gravitational redshift and Doppler shift, the transport of the polarization vector along the ray, and the ellipticity of the plasma eigenmodes.
\r\n\r\nThe presence of relativity qualitatively changes the dispersion relation, introducing a third branch. In addition it significantly augments various polarized emission and transfer effects in strongly sheared flows, such as jets. Additionally, we demonstrate that it is possible, due to refraction coupled with the existence of a horizon, to generate a net circular polarization regardless of the intrinsic polarization of the emission mechanism. We find that this is not likely to be of significant importance for circular polarization in AGN (including the Galactic center and M81). However, in the context of X-ray binaries, this may produce measurable circular polarizations in the infrared.
\r\n\r\nWe also develop a formalism for performing polarized radiative transfer through tangled magnetic fields. We find that for Faraday thick plasmas with a net magnetic helicity (but not necessarily a net magnetic field) it is possible to generate a circular polarization fraction which increases with frequency, as is observed to be the case in the Galactic center. In this case the handedness of the circular polarization is determined by the angular momentum of the accretion disk. This mechanism can be applied to extragalactic AGN and naturally explains the low degrees of circular polarization observed. As with the refractive mechanism, this may also be applied to X-ray binaries, and predicts ~10% polarization fractions at infrared wavelengths. Again, this provides a significant motivation for the development of infrared polarimetry.
", "doi": "10.7907/H2PF-K590", "publication_date": "2004", "thesis_type": "phd", "thesis_year": "2004" }, { "id": "thesis:1771", "collection": "thesis", "collection_id": "1771", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05132004-184937", "primary_object_url": { "basename": "psu_thesis.pdf", "content": "final", "filesize": 4115387, "license": "other", "mime_type": "application/pdf", "url": "/1771/1/psu_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "H\u2080 from Cosmic Background Imager Observations of the Sunyaev-Zel\u2019dovich Effect in Nearby Clusters.", "author": [ { "family_name": "Udomprasert", "given_name": "Patricia Simcoe", "clpid": "Udomprasert-Patricia-Simcoe" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Blain", "given_name": "Andrew W.", "clpid": "Blain-A-W" }, { "family_name": "Djorgovski", "given_name": "George", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-G" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "We present H\u2080 results from Cosmic Background Imager (CBI) observations of the Sunyaev-Zeldovich Effect (SZE) in 7 galaxy clusters, A85, A399, A401, A478, A754, A1651, and A2597. These observations are part of a program to study a complete, volume-limited sample of low-redshift (z < 0.1), X-ray selected clusters. Our focus on nearby objects allows us to study a well-defined, orientation unbiased sample, minimizing systematic errors due to cluster asphericity. We use density models derived from ROSAT imaging data and temperature measurements from ASCA and BeppoSAX spectral observations. We quantify in detail sources of error in our derivation of H\u2080, including calibration of the CBI data, density and temperature models from the X-ray data, Cosmic Microwave Background (CMB) primary anisotropy fluctuations, and residuals from radio point source subtraction. From these 7 clusters we obtain a result of Ho = 67+30-18(ran)+15-6(sys) km/s-1 Mpc-1 for an unweighted sample average. The respective quoted errors are random and systematic uncertainties at 68% confidence. The dominant source of error is confusion from intrinsic anisotropy fluctuations. We present results from simulations of an eigenmode weighting analysis that reduce the uncertainties due to CMB in h-1/2 by ~30%.", "doi": "10.7907/VR2Z-MP09", "publication_date": "2004", "thesis_type": "phd", "thesis_year": "2004" }, { "id": "thesis:1771", "collection": "thesis", "collection_id": "1771", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05132004-184937", "primary_object_url": { "basename": "psu_thesis.pdf", "content": "final", "filesize": 4115387, "license": "other", "mime_type": "application/pdf", "url": "/1771/1/psu_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "H\u2080 from Cosmic Background Imager Observations of the Sunyaev-Zel\u2019dovich Effect in Nearby Clusters.", "author": [ { "family_name": "Udomprasert", "given_name": "Patricia Simcoe", "clpid": "Udomprasert-Patricia-Simcoe" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Blain", "given_name": "Andrew W.", "clpid": "Blain-A-W" }, { "family_name": "Djorgovski", "given_name": "George", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-G" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "We present H\u2080 results from Cosmic Background Imager (CBI) observations of the Sunyaev-Zeldovich Effect (SZE) in 7 galaxy clusters, A85, A399, A401, A478, A754, A1651, and A2597. These observations are part of a program to study a complete, volume-limited sample of low-redshift (z < 0.1), X-ray selected clusters. Our focus on nearby objects allows us to study a well-defined, orientation unbiased sample, minimizing systematic errors due to cluster asphericity. We use density models derived from ROSAT imaging data and temperature measurements from ASCA and BeppoSAX spectral observations. We quantify in detail sources of error in our derivation of H\u2080, including calibration of the CBI data, density and temperature models from the X-ray data, Cosmic Microwave Background (CMB) primary anisotropy fluctuations, and residuals from radio point source subtraction. From these 7 clusters we obtain a result of Ho = 67+30-18(ran)+15-6(sys) km/s-1 Mpc-1 for an unweighted sample average. The respective quoted errors are random and systematic uncertainties at 68% confidence. The dominant source of error is confusion from intrinsic anisotropy fluctuations. We present results from simulations of an eigenmode weighting analysis that reduce the uncertainties due to CMB in h-1/2 by ~30%.", "doi": "10.7907/VR2Z-MP09", "publication_date": "2004", "thesis_type": "phd", "thesis_year": "2004" }, { "id": "thesis:2085", "collection": "thesis", "collection_id": "2085", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05262004-231543", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 2232600, "license": "other", "mime_type": "application/pdf", "url": "/2085/1/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Radiative Transfer in Accreting Environments", "author": [ { "family_name": "Broderick", "given_name": "Avery Earl", "orcid": "0000-0002-3351-760X", "clpid": "Broderick-Avery-Earl" } ], "thesis_advisor": [ { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" } ], "thesis_committee": [ { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Thorne", "given_name": "Kip S.", "clpid": "Thorne-K-S" }, { "family_name": "Kamionkowski", "given_name": "Marc P.", "clpid": "Kamionkowski-M-P" } ], "local_group": [ { "literal": "TAPIR" }, { "literal": "div_pma" } ], "abstract": "Accretion onto compact objects plays a central role in high-energy astrophysics. The process of accretion can substantially affect the magnetic field strength and geometry (e.g, via the magneto-rotational instability or dynamo processes) and the accreting plasma density. The presence of the compact object itself can significantly affect the character and structure of the accreting plasma as well as its emission. This is especially true, in the case of an accreting black hole, when a significant fraction of the emission originates or passes near the horizon. To address this, we develop a manifestly covariant magnetoionic theory, capable of tracing rays in the geometric optics approximation through a magnetized plasma in a general relativistic environment. This is discussed for both the cold and warm, ion and pair plasmas. We also address the problem of performing polarized radiative transfer covariantly in these environments, considering in particular the anisotropic nature of magnetized plasmas, the gravitational redshift and Doppler shift, the transport of the polarization vector along the ray, and the ellipticity of the plasma eigenmodes.
\r\n\r\nThe presence of relativity qualitatively changes the dispersion relation, introducing a third branch. In addition it significantly augments various polarized emission and transfer effects in strongly sheared flows, such as jets. Additionally, we demonstrate that it is possible, due to refraction coupled with the existence of a horizon, to generate a net circular polarization regardless of the intrinsic polarization of the emission mechanism. We find that this is not likely to be of significant importance for circular polarization in AGN (including the Galactic center and M81). However, in the context of X-ray binaries, this may produce measurable circular polarizations in the infrared.
\r\n\r\nWe also develop a formalism for performing polarized radiative transfer through tangled magnetic fields. We find that for Faraday thick plasmas with a net magnetic helicity (but not necessarily a net magnetic field) it is possible to generate a circular polarization fraction which increases with frequency, as is observed to be the case in the Galactic center. In this case the handedness of the circular polarization is determined by the angular momentum of the accretion disk. This mechanism can be applied to extragalactic AGN and naturally explains the low degrees of circular polarization observed. As with the refractive mechanism, this may also be applied to X-ray binaries, and predicts ~10% polarization fractions at infrared wavelengths. Again, this provides a significant motivation for the development of infrared polarimetry.
", "doi": "10.7907/H2PF-K590", "publication_date": "2004", "thesis_type": "phd", "thesis_year": "2004" }, { "id": "thesis:2191", "collection": "thesis", "collection_id": "2191", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05282004-140350", "primary_object_url": { "basename": "main.pdf", "content": "final", "filesize": 2998326, "license": "other", "mime_type": "application/pdf", "url": "/2191/1/main.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Data Analysis of and Results from Observations of the Cosmic Microwave Background with the Cosmic Background Imager", "author": [ { "family_name": "Sievers", "given_name": "Jonathan LeRoy", "orcid": "0000-0001-6903-5074", "clpid": "Sievers-Jonathan-LeRoy" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Steidel", "given_name": "Charles C.", "orcid": "0000-0002-4834-7260", "clpid": "Steidel-C-C" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Kamionkowski", "given_name": "Marc P.", "orcid": "0000-0001-7018-2055", "clpid": "Kamionkowski-M-P" }, { "family_name": "Pearson", "given_name": "Timothy J.", "orcid": "0000-0001-5213-6231", "clpid": "Pearson-T-J" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "We present results from observations of the Cosmic Microwave Background (CMB) with the Cosmic Background Imager (CBI), a sensitive 13-element interferometer located high in the Chilean Andes. We also discuss methods of analyzing the data from the CBI, including an improved way of measuring the true power spectrum using maximum likelihood estimation. This improved method leads to a saving of a factor of two in memory usage, and an increase in speed of order the number of points in the spectrum. The initial results are discussed, in which the fall-off in power at ell > 1000 (the \"damping tail\") was first observed. We also present the results from the first year of observations with the CBI, and discuss cosmological intepretations both alone and in concert with the results from other experiments. These provide tight constraints on cosmological parameters, including a Hubble constant of 69 +/- 4 km/s/Mpc, an age of the universe of 13.7 +/- 0.2 billion years, and a denisty of dark energy of 0.70 +/- 0.05 of the critical density of the universe. Finally, we discuss an alternate method of data compression, with great flexibility in what information is kept, while being computationally tractable. We then apply this method to the CBI data to constrain the potential emission from foreground contaminants contributing to the observed CMB radiation. We find that the data is consistent with zero foreground, with a maximum allowed foreground contribution between about 8% and 12% of the total signal (at an ell of 600 and frequency of 30 GHz), depending on the spectral index of foreground emission.\r\n", "doi": "10.7907/8706-VY52", "publication_date": "2004", "thesis_type": "phd", "thesis_year": "2004" }, { "id": "thesis:2230", "collection": "thesis", "collection_id": "2230", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05292003-131234", "primary_object_url": { "basename": "jkc_thesis.pdf", "content": "final", "filesize": 6078828, "license": "other", "mime_type": "application/pdf", "url": "/2230/1/jkc_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "A Limit on the Polarization of the Cosmic Microwave Background Radiation", "author": [ { "family_name": "Cartwright", "given_name": "John Kenneth", "clpid": "Cartwright-John-Kenneth" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Zmuidzinas", "given_name": "Jonas", "orcid": "0000-0002-3330-5439", "clpid": "Zmuidzinas-J" }, { "family_name": "Padin", "given_name": "Stephen", "orcid": "0009-0001-9993-4393", "clpid": "Padin-Stephen" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "We describe polarization observations of the CMBR with the Cosmic Background Imager, a 13-element interferometer which operates in the 26-36 GHz band and is located on the Llano de Chajnantor in northern Chile. The array consists of 90 cm Cassegrain antennas mounted on a steerable platform which can be rotated about the optical axis to facilitate polarization observations. The CBI employs single-mode circularly polarized receivers and it samples multipoles from \u2113 ~ 400 to \u2113 ~ 4250. The instrumental polarization of the CBI was calibrated with 3C279, a bright polarized point source which was monitored with the VLA. Observations of two deep fields during the 2000 season yielded three limits (95% c.l.) for C\u2113EE under the assumption that C\u2113BB = 0: 7.0 \u00b5K (\u2113 = 603); 12.8 \u00b5K (\u2113 = 1144); and 25.1 \u00b5K (\u2113 = 2048). The low-\u2113 limit approaches the levels of fluctuations predicted by standard models.
\r\n\r\nThis thesis also entailed the design and implementation of several major components of the CBI signal chain including the downconverter, the noise calibration system, and the low noise HEMT amplifiers. We discuss the design and performance of these critical systems.
", "doi": "10.7907/D3CT-YV96", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:2230", "collection": "thesis", "collection_id": "2230", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05292003-131234", "primary_object_url": { "basename": "jkc_thesis.pdf", "content": "final", "filesize": 6078828, "license": "other", "mime_type": "application/pdf", "url": "/2230/1/jkc_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "A Limit on the Polarization of the Cosmic Microwave Background Radiation", "author": [ { "family_name": "Cartwright", "given_name": "John Kenneth", "clpid": "Cartwright-John-Kenneth" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Zmuidzinas", "given_name": "Jonas", "orcid": "0000-0002-3330-5439", "clpid": "Zmuidzinas-J" }, { "family_name": "Padin", "given_name": "Stephen", "orcid": "0009-0001-9993-4393", "clpid": "Padin-Stephen" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "We describe polarization observations of the CMBR with the Cosmic Background Imager, a 13-element interferometer which operates in the 26-36 GHz band and is located on the Llano de Chajnantor in northern Chile. The array consists of 90 cm Cassegrain antennas mounted on a steerable platform which can be rotated about the optical axis to facilitate polarization observations. The CBI employs single-mode circularly polarized receivers and it samples multipoles from \u2113 ~ 400 to \u2113 ~ 4250. The instrumental polarization of the CBI was calibrated with 3C279, a bright polarized point source which was monitored with the VLA. Observations of two deep fields during the 2000 season yielded three limits (95% c.l.) for C\u2113EE under the assumption that C\u2113BB = 0: 7.0 \u00b5K (\u2113 = 603); 12.8 \u00b5K (\u2113 = 1144); and 25.1 \u00b5K (\u2113 = 2048). The low-\u2113 limit approaches the levels of fluctuations predicted by standard models.
\r\n\r\nThis thesis also entailed the design and implementation of several major components of the CBI signal chain including the downconverter, the noise calibration system, and the low noise HEMT amplifiers. We discuss the design and performance of these critical systems.
", "doi": "10.7907/D3CT-YV96", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:1884", "collection": "thesis", "collection_id": "1884", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05202002-104244", "primary_object_url": { "basename": "0_Complete_Thesis.pdf", "content": "final", "filesize": 12416662, "license": "other", "mime_type": "application/pdf", "url": "/1884/1/0_Complete_Thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "1:1 Motif for DNA Recognition by \u03b2-Alanine Linked Polyamides", "author": [ { "family_name": "Urbach", "given_name": "Adam Robert", "orcid": "0000-0003-3426-4760", "clpid": "Urbach-Adam-Robert" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Dervan", "given_name": "Peter B.", "orcid": "0000-0001-8852-7306", "clpid": "Dervan-P-B" } ], "thesis_committee": [ { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Dervan", "given_name": "Peter B.", "orcid": "0000-0001-8852-7306", "clpid": "Dervan-P-B" }, { "family_name": "Roberts", "given_name": "Richard W.", "orcid": "0000-0002-8587-5097", "clpid": "Roberts-R-W" }, { "family_name": "Mayo", "given_name": "Stephen L.", "orcid": "0000-0002-9785-5018", "clpid": "Mayo-S-L" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Polyamides composed of N-methylpyrrole (Py), N-methylimidazole (Im), and 3-hydroxypyrrole (Hp) amino acids linked by beta-alanine (beta) bind in the minor groove of DNA in 1:1 and 2:1 ligand:DNA complexes. Although the energetics and structure of the 2:1 motif have been explored extensively, there is remarkably less understood about 1:1 recognition beyond the initial studies on netropsin and distamycin. Laemmli and coworkers used beta-linked polyamides, which bind in a 1:1 motif, to effect phenotypic changes in Drosophila melanogaster. The thesis work described here investigates Laemmli's 1:1 motif in order to further understand and exploit this novel mode of DNA recognition.
\r\n\r\ny selectively replacing Py residues with beta it was found that the Im-beta-Im subunit is important for high-affinity binding in 1:1 and 2:1 modes. This study also demonstrates that a single ligand can target very different DNA sequences based on 1:1 or 2:1 binding. This ambiguity of sequence targeting based on stoichiometry was addressed. It was discovered that hairpin and 1:1 binding modes, which are dependent on ligand conformation, are controlled by changing the linker between polyamide subunits.
\r\n\r\nThe possibility of developing a 1:1 recognition code was explored by selectively mutating polyamide residues and DNA base pairs and comparing the association constants for the resulting complexes. It was found that Im residues tolerate all four Watson-Crick base pairs; Py and beta residues are specific for A?T and T?A base pairs; and Hp specifies a single base pair, A?T, in the sequence context 5'-AAAGAGAAGAG-3'. Attempts to improve upon this recognition code using novel heterocyclic amino acids, such as furan, thiophene, thiazole, and hydroxythiophene, are presented. The sequence-dependence of ligand orientation and the effect of ligand size on binding affinity were also explored.
\r\n\r\nThe NMR structure of a 1:1 polyamide:DNA complex was determined. It reveals B-form DNA with a narrow minor groove and large negative propeller twist, which are shown to be stabilized by bifurcated hydrogen bonds between polyamide NH groups and purine N3 and pyrimidine O2 atoms. The first direct evidence is provided for hydrogen bond formation between Im-N3 and guanine NH2 in the 1:1 motif, thus confirming the original lexitropsin model.
", "doi": "10.7907/V6FD-YQ78", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6367", "collection": "thesis", "collection_id": "6367", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05022011-085219561", "primary_object_url": { "basename": "Halverson_nw_2002.pdf", "content": "final", "filesize": 38458756, "license": "other", "mime_type": "application/pdf", "url": "/6367/1/Halverson_nw_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "A Measurement of the Cosmic Microwave Background Angular Power Spectrum with DASI", "author": [ { "family_name": "Halverson", "given_name": "Nils William", "clpid": "Halverson-Nils-William" } ], "thesis_advisor": [ { "family_name": "Carlstrom", "given_name": "John E.", "clpid": "Carlstrom-J-E" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Carlstrom", "given_name": "John E.", "clpid": "Carlstrom-J-E" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Phillips", "given_name": "Thomas G.", "clpid": "Phillips-T-G" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The Cosmic Microwave Background (CMB) has long been recognized as an astounding source of information about the early Universe. In this thesis we describe the design,\r\nimplementation, and first-year results of the Degree Angular Scale Interferometer (DASI), a compact interferometer designed to measure the angular power spectrum of the CMB. We discuss details of the optics, receivers, and power spectrum analysis, including the use of constraint matrices to project out contaminants and test for correlations with diffuse foreground templates.\r\n\r\nWe present a measurement of the CMB angular power spectrum in the multipole range l \u2248 100- 900 in nine bands. The measured fluctuations have a temperature spectral index of \u03b2 = -0.1 \u00b1 0.2 (1\u03c3) consistent with CMB. We find no evidence of foregrounds other than point sources in the data. We detect a first peak in the power spectrum at l ~ 200, a second peak in the power spectrum at l ~ 550, and a rise in the power spectrum at l ~ 800 which is indicative of a third, consistent with inflationary theories. \r\n\r\nUsing the DASI measurement along with COBE DMR data, and adopting conservative priors on the Hubble parameter h > 0.45 and an optical depth due to reionization 0.0 \u2264 \u03c4_c \u2264 0.4, we constrain the total density of the Universe \u03a9_(tot) = 1.04 \u00b1 0.06, the spectral index of the primordial density fluctuations n_s = 1.01^(+0.08)_(-0.06), and the physical baryon density \u03a9_bh^2 = 0.022^(+0.004)_(-0.003) among others (all 68% confidence limits). These constraints are consistent with inflation and estimates of \u03a9_bh^2 from Big Bang Nucleosynthesis. With prior h = 0.72 \u00b1 0.08, we constrain the matter density \u03a9_m = 0.40 \u00b1 0.15, and the vacuum energy density \u03a9_\u039b = 0.60 \u00b1 0.15, indicating from CMB data the presence of dark matter and dark energy in the Universe.", "doi": "10.7907/BEJN-HQ49", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6367", "collection": "thesis", "collection_id": "6367", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05022011-085219561", "primary_object_url": { "basename": "Halverson_nw_2002.pdf", "content": "final", "filesize": 38458756, "license": "other", "mime_type": "application/pdf", "url": "/6367/1/Halverson_nw_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "A Measurement of the Cosmic Microwave Background Angular Power Spectrum with DASI", "author": [ { "family_name": "Halverson", "given_name": "Nils William", "clpid": "Halverson-Nils-William" } ], "thesis_advisor": [ { "family_name": "Carlstrom", "given_name": "John E.", "clpid": "Carlstrom-J-E" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Carlstrom", "given_name": "John E.", "clpid": "Carlstrom-J-E" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Phillips", "given_name": "Thomas G.", "clpid": "Phillips-T-G" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The Cosmic Microwave Background (CMB) has long been recognized as an astounding source of information about the early Universe. In this thesis we describe the design,\r\nimplementation, and first-year results of the Degree Angular Scale Interferometer (DASI), a compact interferometer designed to measure the angular power spectrum of the CMB. We discuss details of the optics, receivers, and power spectrum analysis, including the use of constraint matrices to project out contaminants and test for correlations with diffuse foreground templates.\r\n\r\nWe present a measurement of the CMB angular power spectrum in the multipole range l \u2248 100- 900 in nine bands. The measured fluctuations have a temperature spectral index of \u03b2 = -0.1 \u00b1 0.2 (1\u03c3) consistent with CMB. We find no evidence of foregrounds other than point sources in the data. We detect a first peak in the power spectrum at l ~ 200, a second peak in the power spectrum at l ~ 550, and a rise in the power spectrum at l ~ 800 which is indicative of a third, consistent with inflationary theories. \r\n\r\nUsing the DASI measurement along with COBE DMR data, and adopting conservative priors on the Hubble parameter h > 0.45 and an optical depth due to reionization 0.0 \u2264 \u03c4_c \u2264 0.4, we constrain the total density of the Universe \u03a9_(tot) = 1.04 \u00b1 0.06, the spectral index of the primordial density fluctuations n_s = 1.01^(+0.08)_(-0.06), and the physical baryon density \u03a9_bh^2 = 0.022^(+0.004)_(-0.003) among others (all 68% confidence limits). These constraints are consistent with inflation and estimates of \u03a9_bh^2 from Big Bang Nucleosynthesis. With prior h = 0.72 \u00b1 0.08, we constrain the matter density \u03a9_m = 0.40 \u00b1 0.15, and the vacuum energy density \u03a9_\u039b = 0.60 \u00b1 0.15, indicating from CMB data the presence of dark matter and dark energy in the Universe.", "doi": "10.7907/BEJN-HQ49", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6796", "collection": "thesis", "collection_id": "6796", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01302012-162107660", "primary_object_url": { "basename": "Lithwick_y_2002.pdf", "content": "final", "filesize": 28809074, "license": "other", "mime_type": "application/pdf", "url": "/6796/1/Lithwick_y_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Topics in MHD Turbulence", "author": [ { "family_name": "Lithwick", "given_name": "Yoram", "orcid": "0000-0003-4450-0528", "clpid": "Lithwick-Yoram" } ], "thesis_advisor": [ { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "TAPIR" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "I consider two topics in MHD turbulence. First, I work out the theory of compressible MHD turbulence, including kinetic effects. I use this theory to understand features of interstellar scintillation that have hitherto been unexplained. Second, I work out the theory of imbalanced weak MHD turbulence.", "doi": "10.7907/FP3Q-EZ29", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6796", "collection": "thesis", "collection_id": "6796", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01302012-162107660", "primary_object_url": { "basename": "Lithwick_y_2002.pdf", "content": "final", "filesize": 28809074, "license": "other", "mime_type": "application/pdf", "url": "/6796/1/Lithwick_y_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Topics in MHD Turbulence", "author": [ { "family_name": "Lithwick", "given_name": "Yoram", "orcid": "0000-0003-4450-0528", "clpid": "Lithwick-Yoram" } ], "thesis_advisor": [ { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "TAPIR" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "I consider two topics in MHD turbulence. First, I work out the theory of compressible MHD turbulence, including kinetic effects. I use this theory to understand features of interstellar scintillation that have hitherto been unexplained. Second, I work out the theory of imbalanced weak MHD turbulence.", "doi": "10.7907/FP3Q-EZ29", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6786", "collection": "thesis", "collection_id": "6786", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01272012-091128549", "primary_object_url": { "basename": "Philhour_bj_2002.pdf", "content": "final", "filesize": 27919875, "license": "other", "mime_type": "application/pdf", "url": "/6786/1/Philhour_bj_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Measurement of the Polarization of the Cosmic Microwave Background", "author": [ { "family_name": "Philhour", "given_name": "Byron Jacob", "clpid": "Philhour-Byron-Jacob" } ], "thesis_advisor": [ { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Hughes", "given_name": "Emlyn Willard", "clpid": "Hughes-Emlyn-Willard" } ], "thesis_committee": [ { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Phillips", "given_name": "Thomas G.", "clpid": "Phillips-T-G" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Hughes", "given_name": "Emlyn Willard", "clpid": "Hughes-Emlyn-Willard" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Measurement of cosmic microwave background (CMB) polarization will provide a powerful check on the model that describes CMB \u0394T fluctuations as arising from density fluctuations in the early universe, break degeneracies between cosmological parameters that arise in interpreting \u0394T fluctuations, and may ultimately allow detection of the stochastic gravity-wave background predicted by inflationary models. We describe the development and laboratory characterization of a bolometric experiment designed to measure the arcminute-scale polarization of the CMB. The Polatron receiver will be mounted at the Cassegrain focus of the 5.5 m telescope at the Owens Valley Radio Observatory. The receiver will measure both the Q and U Stokes parameters over a 20% pass-band centered near 100 GHz, with the input polarization signal modulated at ~ 1 Hz by a rotating, birefringent, quartz half-wave plate. In six months of observation we plan to observe ~ 400 2.5 arcminute pixels in a ring about the North Celestial Pole to a precision of ~ 5 \u00b5K per pixel in each of Q and U, adequate to unambiguously detect CMB polarization at levels predicted by current models.", "doi": "10.7907/5333-vh17", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6786", "collection": "thesis", "collection_id": "6786", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01272012-091128549", "primary_object_url": { "basename": "Philhour_bj_2002.pdf", "content": "final", "filesize": 27919875, "license": "other", "mime_type": "application/pdf", "url": "/6786/1/Philhour_bj_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Measurement of the Polarization of the Cosmic Microwave Background", "author": [ { "family_name": "Philhour", "given_name": "Byron Jacob", "clpid": "Philhour-Byron-Jacob" } ], "thesis_advisor": [ { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Hughes", "given_name": "Emlyn Willard", "clpid": "Hughes-Emlyn-Willard" } ], "thesis_committee": [ { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Phillips", "given_name": "Thomas G.", "clpid": "Phillips-T-G" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Hughes", "given_name": "Emlyn Willard", "clpid": "Hughes-Emlyn-Willard" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Measurement of cosmic microwave background (CMB) polarization will provide a powerful check on the model that describes CMB \u0394T fluctuations as arising from density fluctuations in the early universe, break degeneracies between cosmological parameters that arise in interpreting \u0394T fluctuations, and may ultimately allow detection of the stochastic gravity-wave background predicted by inflationary models. We describe the development and laboratory characterization of a bolometric experiment designed to measure the arcminute-scale polarization of the CMB. The Polatron receiver will be mounted at the Cassegrain focus of the 5.5 m telescope at the Owens Valley Radio Observatory. The receiver will measure both the Q and U Stokes parameters over a 20% pass-band centered near 100 GHz, with the input polarization signal modulated at ~ 1 Hz by a rotating, birefringent, quartz half-wave plate. In six months of observation we plan to observe ~ 400 2.5 arcminute pixels in a ring about the North Celestial Pole to a precision of ~ 5 \u00b5K per pixel in each of Q and U, adequate to unambiguously detect CMB polarization at levels predicted by current models.", "doi": "10.7907/5333-vh17", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6982", "collection": "thesis", "collection_id": "6982", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04262012-150437308", "primary_object_url": { "basename": "Wurtz_nr_2002.pdf", "content": "final", "filesize": 7990180, "license": "other", "mime_type": "application/pdf", "url": "/6982/1/Wurtz_nr_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Sequence Specific Alkylation of DNA by Polyamide-Chlorambucil Conjugates", "author": [ { "family_name": "Wurtz", "given_name": "Nicholas Roland", "orcid": "0000-0003-2574-9440", "clpid": "Wurtz-Nicholas-Roland" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Myers", "given_name": "Andrew G.", "orcid": "0000-0001-9602-6915", "clpid": "Myers-A-G" } ], "thesis_committee": [ { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" }, { "family_name": "Dervan", "given_name": "Peter B.", "orcid": "0000-0001-8852-7306", "clpid": "Dervan-P-B" }, { "family_name": "MacMillan", "given_name": "David W. C.", "orcid": "0000-0003-3352-4532", "clpid": "MacMillan-D-W-C" }, { "family_name": "Mayo", "given_name": "Stephen L.", "orcid": "0000-0002-9785-5018", "clpid": "Mayo-S-L" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Myers", "given_name": "Andrew G.", "orcid": "0000-0001-9602-6915", "clpid": "Myers-A-G" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Small molecules that bind selectively to a DNA sequence in the human genome are potentially useful tools for molecular biology and human medicine. Polyamides containing N-methylimidazole (Im) and N-methylpyrrole (Py) are small molecules that bind DNA according to a set of \"pairing rules\" with affinities and specificities similar to many naturally occurring DNA binding proteins. Two alternate routes of synthesis of polyamides are presented that allowed improved synthesis of commonly used motifs as well as access to polyamides with truncated tails which increase the number of DNA sequences targetable by polyamides with high affinity. Py-Im polyamides may offer a general approach to chemical regulation of gene expression provided inhibition of DNA binding for a variety of transcription factor families can be achieved. Two successful strategies are shown for the inhibition of DNA binding by two such proteins, GCN4 and NF-\u03baB. An alternate method of gene regulation would be inhibition of transcription during the elongation phase by site-specific alkylation in the coding region of genes. A new class of compounds is created by the attachment of a bis (dichloroethylamino)-benzene nonspecific DNA alkylator to polyamides, which alkylate DNA with high yield and specificity. The biological activity and cell permeability of one of these compounds in several systems is studied.
", "doi": "10.7907/59jz-2e47", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:2567", "collection": "thesis", "collection_id": "2567", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06132002-131531", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 1449979, "license": "other", "mime_type": "application/pdf", "url": "/2567/1/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Hard X-Ray Observations of the Extragalactic Sky: The High Energy Focusing Telescope and the Serendipitous Extragalactic X-ray Source Identification Survey", "author": [ { "family_name": "Mao", "given_name": "Peter Hsih-Jen", "clpid": "Mao-Peter-Hsih-Jen" } ], "thesis_advisor": [ { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" } ], "thesis_committee": [ { "family_name": "Harrison", "given_name": "Fiona A.", "orcid": "0000-0003-2992-8024", "clpid": "Harrison-F-A" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" } ], "local_group": [ { "literal": "Space Radiation Laboratory" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Extending the energy range of high sensitivity astronomical x-ray observations to the hard x-ray band (10-100 keV) is important for the study of nonthermal emission mechanisms and heavily obscured sources. This thesis, in two parts, describes the development of the High Energy Focusing Telescope (HEFT), a focusing telescope for the hard x-ray band, and the Serendipitous Extragalactic X-ray Source Identification (SEXSI) survey, a degree-scale x-ray/optical survey of sources detected in the Chandra hard band (2-7 keV).
\r\n\r\nHEFT is a balloon-borne x-ray telescope that is expected to have its first flight in the fall of 2003. The telescope will be among the first to focus x-rays at energies greater than 20 keV. HEFT's mirrors use graded multilayers -- thin film coatings (~1 \u00b5m) that enhance high energy reflectance via constructive interference. In the first half of the thesis, I describe the optimization algorithm that I developed for x-ray optics and how I applied this algorithm to the design of the HEFT optics. In addition, I present x-ray measurements that verify the HEFT multilayer coating designs at energies where the telescope will operate.
\r\n\r\nThe SEXSI survey complements Chandra deep-field surveys by covering a much larger area of the sky, but to a shallower x-ray flux limit. For the SEXSI survey, we use public data from the Chandra archive to compile a catalog of extragalactic sources detected in the 2-7 keV band. We identify the optical counterparts to the x-ray sources and obtain their optical spectra (400-1000 nm). Presently SEXSI includes 30 Chandra fields, covering roughly 2 square degrees and yielding over 1200 x-ray sources to a flux limit of 10\u207b\u00b9\u2075-10\u207b\u00b9\u00b3 erg cm\u207b\u00b2 s\u207b\u00b9. In the second part of the thesis, I present results from 10 fields for which we have substantial spectroscopic coverage.
", "doi": "10.7907/R5E3-RQ86", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6996", "collection": "thesis", "collection_id": "6996", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05012012-101216772", "primary_object_url": { "basename": "Wang_ccc_2002.pdf", "content": "final", "filesize": 5350283, "license": "other", "mime_type": "application/pdf", "url": "/6996/1/Wang_ccc_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Sequence Specific Trapping of Topoisomerase I by Camptothecin Polyamide Conjugates", "author": [ { "family_name": "Wang", "given_name": "Clay Chia Chun", "clpid": "Wang-Clay-Chia-Chun" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Dervan", "given_name": "Peter B.", "orcid": "0000-0001-8852-7306", "clpid": "Dervan-P-B" } ], "thesis_committee": [ { "family_name": "Rees", "given_name": "Douglas C.", "orcid": "0000-0003-4073-1185", "clpid": "Rees-D-C" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Dervan", "given_name": "Peter B.", "orcid": "0000-0001-8852-7306", "clpid": "Dervan-P-B" }, { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" }, { "family_name": "Roberts", "given_name": "Richard W.", "clpid": "Roberts-R-W" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Polyamides containing N-methylpyrrole (Py)N-methylimidazole (Im) and 3-hydroxy-1-methylpyrrole (Hp) are cell permeable small molecules that bind as antiparallel pairs in the minor groove of DNA according to a set of \"pairing rules\" with affinities and specificities for predetermined sequences comparable to DNA-binding proteins. Several of these ring pairings have only been demonstrated when placed internal in a hairpin and not for the terminal position in hairpin polyamides. Several series of eight ring hairpin polyamides with modification at the N-terminal position were synthesized and characterized. We observed that at the terminal position (i) the Py/Py pair functions similar to when placed internally preferring A\u2022T and T\u2022A base pairs over O\u2022C and C\u2022O, (ii) the Hp/Py pair could not distinguish between T\u2022A over A-T possibly due to rotation of the terminal Hp to form an intramolecular hydrogen bond between the 3-hydroxyl hydrogen and the carboxamide oxygen which would orient the key hydroxyl recognition element away from the minor groove. A new aromatic pair, 2-hydroxy-6-methoxybenzamidell-methylpyrrole was designed and shown to distinguish T\u2022A from A\u2022T base pairs and both from O\u2022C/C\u2022O and (iii) the Py/Im pair in the classic eight ring hairpin motif showed no preference for C\u2022O base pair possibly due to the mispositioning of the Im residue located at the C-terminal end of the four ring polyamide subunit. Targeting of C\u2022O was accomplished by replacing a pyrrole with a flexible \u03b2-alanine and setting the imidazole back in register.
\r\n\r\nPyrrole-imidazole polyamides that target DNA sequences in the promoter have been shown to inhibit transcription of specific genes in cell culture. When bound to coding region of genes, polyamides do not appear to inhibit gene expression. A possible solution is to design molecule capable of modifying DNA when bound to the coding region. A series of polyamide-camptothecin conjugates were designed to trap the enzyme Topoisomerase I and induce cleavage at predetermined DNA sites. Cleavage yields were shown to be dependent on linker length between the DNA binding polyamide\r\nand the Topo I trapping camptothecin unit with the camptothecin unit with the longest linker showing greatest cleavage yield of over 90%.
\r\n", "doi": "10.7907/sphn-ma74", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:1680", "collection": "thesis", "collection_id": "1680", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05082006-143046", "primary_object_url": { "basename": "Cornu_c_2002.pdf", "content": "final", "filesize": 5807149, "license": "other", "mime_type": "application/pdf", "url": "/1680/1/Cornu_c_2002.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Photocatalysis Under Periodic Illumination", "author": [ { "family_name": "Cornu", "given_name": "Catherine J. G.", "clpid": "Cornu-Catherine-J-G" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Hering", "given_name": "Janet G.", "clpid": "Hering-J-G" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In the first part of this work, the use of periodic illumination is investigated as a means to improve the quantum yield of aqueous phase photocatalysis. We find that quantum yield enhancements are obtained under periodic illumination compared to those under continuous illumination with the same maximum photon absorption rate. This result is in agreement with previous literature reports. However, no enhancements are obtained when compared to those under continuous illumination with the same average photon absorption rate. Ways in which the use of periodic illumination in remediation systems might nevertheless be more cost-effective than continuous operation are discussed. In the second part of this work, periodic illumination is applied as a tool to investigate the kinetic behavior of the intermediates involved in photocatalysis. Two transitions are observed in the quantum yield as a function of the active light period, corresponding to separate lifetimes of two intermediates. These lifetimes are found to be relatively insensitive to the physical properties of the TiO2 photocatalyst particles, the compound being photocatalytically oxidized, or the oxygen concentration. However, a strong correlation with the pH of the solution is observed. For example, one intermediate's lifetime increases exponentially with pH, while the other one's decreases exponentially. Principles from electrochemistry, namely Nernst's law and the Butler-Volmer equation, allow us to conclude that the intermediate with a decreasing lifetime with pH is a reducing species, while the other one is an oxidizing species. The intermediates' lifetimes are equal at a pH ~ 8, concurrent with a minimum in quantum yield. Below pH 8 the reducing species has a longer lifetime, indicating that interfacial electron transfer to oxygen is the slowest step under these conditions.
\r\n\r\nThe observed lifetimes are compatible with those previously measured for superoxide radicals (reducing species), and hydroxyl radicals, surface trapped holes, or surface bound hydroxyl radicals (oxidizing species).
", "doi": "10.7907/ZDAH-V967", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:1680", "collection": "thesis", "collection_id": "1680", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05082006-143046", "primary_object_url": { "basename": "Cornu_c_2002.pdf", "content": "final", "filesize": 5807149, "license": "other", "mime_type": "application/pdf", "url": "/1680/1/Cornu_c_2002.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Photocatalysis Under Periodic Illumination", "author": [ { "family_name": "Cornu", "given_name": "Catherine J. G.", "clpid": "Cornu-Catherine-J-G" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Hering", "given_name": "Janet G.", "clpid": "Hering-J-G" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In the first part of this work, the use of periodic illumination is investigated as a means to improve the quantum yield of aqueous phase photocatalysis. We find that quantum yield enhancements are obtained under periodic illumination compared to those under continuous illumination with the same maximum photon absorption rate. This result is in agreement with previous literature reports. However, no enhancements are obtained when compared to those under continuous illumination with the same average photon absorption rate. Ways in which the use of periodic illumination in remediation systems might nevertheless be more cost-effective than continuous operation are discussed. In the second part of this work, periodic illumination is applied as a tool to investigate the kinetic behavior of the intermediates involved in photocatalysis. Two transitions are observed in the quantum yield as a function of the active light period, corresponding to separate lifetimes of two intermediates. These lifetimes are found to be relatively insensitive to the physical properties of the TiO2 photocatalyst particles, the compound being photocatalytically oxidized, or the oxygen concentration. However, a strong correlation with the pH of the solution is observed. For example, one intermediate's lifetime increases exponentially with pH, while the other one's decreases exponentially. Principles from electrochemistry, namely Nernst's law and the Butler-Volmer equation, allow us to conclude that the intermediate with a decreasing lifetime with pH is a reducing species, while the other one is an oxidizing species. The intermediates' lifetimes are equal at a pH ~ 8, concurrent with a minimum in quantum yield. Below pH 8 the reducing species has a longer lifetime, indicating that interfacial electron transfer to oxygen is the slowest step under these conditions.
\r\n\r\nThe observed lifetimes are compatible with those previously measured for superoxide radicals (reducing species), and hydroxyl radicals, surface trapped holes, or surface bound hydroxyl radicals (oxidizing species).
", "doi": "10.7907/ZDAH-V967", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:1512", "collection": "thesis", "collection_id": "1512", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04262005-152703", "primary_object_url": { "basename": "Kee_s_2002.pdf", "content": "final", "filesize": 36463553, "license": "other", "mime_type": "application/pdf", "url": "/1512/1/Kee_s_2002.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Class E/F Family of Harmonic-Tuned Switching Power Amplifiers", "author": [ { "family_name": "Kee", "given_name": "Scott David", "clpid": "Kee-Scott-David" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" }, { "family_name": "McEliece", "given_name": "Robert J.", "clpid": "McEliece-R-J" }, { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nA new family of harmonic-tuned switching amplifiers is introduced having the beneficial features of the class-E tuning while allowing improved performance to be achieved through additional harmonic tuning. This E/F family may be tuned to achieve the ZVS/ZdVS switching features characteristic of the class-E amplifier and, like the class-E tuning, accounts and compensates for the effect of the switch parallel capacitance. By tuning one or more overtones to the [...] tuning, however, the switching waveforms may be improved, lowering the peak voltage and reducing the RMS current. Additionally, the tolerance to large switch parallel capacitance is generally improved so that a larger switching device may be used, allowing reduction of the on-resistance. Due to these factors, the efficiency of E/F amplifiers is expected to exceed that of class E.\r\n\r\nTo demonstrate these advantages, methods of estimating the optimal efficiency of switching amplifiers using waveform properties are given. A general solution technique is then presented which allows the calculation of the ZVS tuning requirements and the resulting switching waveforms for an arbitrary harmonic tuning. Using these two tools, switching waveforms and resulting efficiency estimates are calculated for E/F amplifier tunings, which are then compared to class E.\r\n\r\nFinally, potential application areas of the E/F technique are explored, and measured results of several first-generation E/F amplifiers are presented. Aside from efficiency benefits, E/F amplifiers also may achieve load-invariance, dual- and multi-band operation, high volumetric power densities, and efficient integrated circuit implementation using the Aoki distributed active transformer power combining structure.\r\n", "doi": "10.7907/MD86-FX51", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:1512", "collection": "thesis", "collection_id": "1512", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04262005-152703", "primary_object_url": { "basename": "Kee_s_2002.pdf", "content": "final", "filesize": 36463553, "license": "other", "mime_type": "application/pdf", "url": "/1512/1/Kee_s_2002.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Class E/F Family of Harmonic-Tuned Switching Power Amplifiers", "author": [ { "family_name": "Kee", "given_name": "Scott David", "clpid": "Kee-Scott-David" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" }, { "family_name": "McEliece", "given_name": "Robert J.", "clpid": "McEliece-R-J" }, { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nA new family of harmonic-tuned switching amplifiers is introduced having the beneficial features of the class-E tuning while allowing improved performance to be achieved through additional harmonic tuning. This E/F family may be tuned to achieve the ZVS/ZdVS switching features characteristic of the class-E amplifier and, like the class-E tuning, accounts and compensates for the effect of the switch parallel capacitance. By tuning one or more overtones to the [...] tuning, however, the switching waveforms may be improved, lowering the peak voltage and reducing the RMS current. Additionally, the tolerance to large switch parallel capacitance is generally improved so that a larger switching device may be used, allowing reduction of the on-resistance. Due to these factors, the efficiency of E/F amplifiers is expected to exceed that of class E.\r\n\r\nTo demonstrate these advantages, methods of estimating the optimal efficiency of switching amplifiers using waveform properties are given. A general solution technique is then presented which allows the calculation of the ZVS tuning requirements and the resulting switching waveforms for an arbitrary harmonic tuning. Using these two tools, switching waveforms and resulting efficiency estimates are calculated for E/F amplifier tunings, which are then compared to class E.\r\n\r\nFinally, potential application areas of the E/F technique are explored, and measured results of several first-generation E/F amplifiers are presented. Aside from efficiency benefits, E/F amplifiers also may achieve load-invariance, dual- and multi-band operation, high volumetric power densities, and efficient integrated circuit implementation using the Aoki distributed active transformer power combining structure.\r\n", "doi": "10.7907/MD86-FX51", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:4089", "collection": "thesis", "collection_id": "4089", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10142008-144557", "primary_object_url": { "basename": "Gal_rr_2001.pdf", "content": "final", "filesize": 40256991, "license": "other", "mime_type": "application/pdf", "url": "/4089/1/Gal_rr_2001.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "The Northern Sky Optical Cluster Survey: Galaxy Clusters from Five Thousand Square Degrees of DPOSS", "author": [ { "family_name": "Gal", "given_name": "Roy R.", "orcid": "0000-0001-8255-6560", "clpid": "Gal-Roy-R" } ], "thesis_advisor": [ { "family_name": "Djorgovski", "given_name": "George", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-G" } ], "thesis_committee": [ { "family_name": "Djorgovski", "given_name": "George", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-G" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Ellis", "given_name": "Richard S.", "clpid": "Ellis-R-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Steidel", "given_name": "Charles C.", "orcid": "0000-0002-4834-7260", "clpid": "Steidel-C-C" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Clusters of galaxies are the largest bound systems in the Universe and, as such, have been used to study how matter is distributed over extremely large scales. They provide fundamental constraints for theories of large-scale structure formation and evolution, and are valuable samples for studying galaxy evolution in dense environments. Despite their importance, the last large-area Northern sky cluster catalog was produced over forty years ago, via visual inspection of photographic plates of POSS-I, presented in George Abell's seminal 1958 paper and thesis. To remedy the limitations of this earlier work, we present a modern, objectively generated catalog of galaxy clusters drawn from the object catalogs of the three-band Digitized Second Palomar Observatory Sky Survey (DPOSS). In this thesis we have undertaken the following:\r\n
This thesis describes BOOMERANG; a balloon-borne telescope and receiver designed to map the Cosmic Microwave Background (CMB) at a resolution of 10' from the Long Duration Balloon (LDB) platform. The millimeter-wave receiver employs new technology in bolometers, readout electronics, cold re-imaging optics, millimeter-wave filters, and cryogenics to obtain high sensitivity to CMB anisotropy. Sixteen detectors observe in 4 spectral bands centered at 90, 150, 240 and 400 GHz. The wide frequency coverage, the long flight duration, the optical design and the observing strategy all provide strong rejection of systematic effects. We report the in-flight performance of the instrument during a short test flight from Palestine, Texas, that mapped 230 square degrees and during a 10.5 day stratospheric balloon flight launched from McMurdo Station, Antarctica, that mapped ~ 2000 square degrees of the sky. The Antarctic data yielded a measurement of the angular power spectrum of the CMB between 50 < \u2113 < 600 which shows a peak at \u2113peak = 197 \u00b1 6 (1\u03c3 error). A maximum likelihood estimation of cosmological parameters within the cold dark matter (CDM) paradigm of structure formation indicates that the universe is flat with a precision of ~ 6% and that the density of baryons in the universe may be slightly higher than previously thought. The combination of observations of large scale structure (LSS) and the BOOMERANG power spectrum implies the presence of both dark matter and dark energy, or the existence of Einstein's cosmological constant.
", "doi": "10.7907/GVJ5-GC44", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:3180", "collection": "thesis", "collection_id": "3180", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08212001-163318", "type": "thesis", "title": "A Measurement of the Angular Power Spectrum of the Cosmic Microwave Background with a Long Duration Balloon-Borne Receiver", "author": [ { "family_name": "Crill", "given_name": "Brendan Patrick", "orcid": "0000-0002-4650-8518", "clpid": "Crill-Brendan-Patrick" } ], "thesis_advisor": [ { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" } ], "thesis_committee": [ { "family_name": "Lange", "given_name": "Andrew E.", "clpid": "Lange-A-E" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This thesis describes BOOMERANG; a balloon-borne telescope and receiver designed to map the Cosmic Microwave Background (CMB) at a resolution of 10' from the Long Duration Balloon (LDB) platform. The millimeter-wave receiver employs new technology in bolometers, readout electronics, cold re-imaging optics, millimeter-wave filters, and cryogenics to obtain high sensitivity to CMB anisotropy. Sixteen detectors observe in 4 spectral bands centered at 90, 150, 240 and 400 GHz. The wide frequency coverage, the long flight duration, the optical design and the observing strategy all provide strong rejection of systematic effects. We report the in-flight performance of the instrument during a short test flight from Palestine, Texas, that mapped 230 square degrees and during a 10.5 day stratospheric balloon flight launched from McMurdo Station, Antarctica, that mapped ~ 2000 square degrees of the sky. The Antarctic data yielded a measurement of the angular power spectrum of the CMB between 50 < \u2113 < 600 which shows a peak at \u2113peak = 197 \u00b1 6 (1\u03c3 error). A maximum likelihood estimation of cosmological parameters within the cold dark matter (CDM) paradigm of structure formation indicates that the universe is flat with a precision of ~ 6% and that the density of baryons in the universe may be slightly higher than previously thought. The combination of observations of large scale structure (LSS) and the BOOMERANG power spectrum implies the presence of both dark matter and dark energy, or the existence of Einstein's cosmological constant.
", "doi": "10.7907/GVJ5-GC44", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:4089", "collection": "thesis", "collection_id": "4089", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10142008-144557", "primary_object_url": { "basename": "Gal_rr_2001.pdf", "content": "final", "filesize": 40256991, "license": "other", "mime_type": "application/pdf", "url": "/4089/1/Gal_rr_2001.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "The Northern Sky Optical Cluster Survey: Galaxy Clusters from Five Thousand Square Degrees of DPOSS", "author": [ { "family_name": "Gal", "given_name": "Roy R.", "orcid": "0000-0001-8255-6560", "clpid": "Gal-Roy-R" } ], "thesis_advisor": [ { "family_name": "Djorgovski", "given_name": "George", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-G" } ], "thesis_committee": [ { "family_name": "Djorgovski", "given_name": "George", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-G" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Ellis", "given_name": "Richard S.", "clpid": "Ellis-R-S" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Steidel", "given_name": "Charles C.", "orcid": "0000-0002-4834-7260", "clpid": "Steidel-C-C" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Clusters of galaxies are the largest bound systems in the Universe and, as such, have been used to study how matter is distributed over extremely large scales. They provide fundamental constraints for theories of large-scale structure formation and evolution, and are valuable samples for studying galaxy evolution in dense environments. Despite their importance, the last large-area Northern sky cluster catalog was produced over forty years ago, via visual inspection of photographic plates of POSS-I, presented in George Abell's seminal 1958 paper and thesis. To remedy the limitations of this earlier work, we present a modern, objectively generated catalog of galaxy clusters drawn from the object catalogs of the three-band Digitized Second Palomar Observatory Sky Survey (DPOSS). In this thesis we have undertaken the following:\r\n
The science of precision millisecond pulsar timing can yield the most precise astrometric measurements ever made. This potential can only be realized through an extraordinary amount of investment in the experimental apparatus, the effort of many observers, and the close attention to details required to avoid the many pitfalls along the way. This thesis describes the work and results from a precision timing project aimed at monitoring the brightest millisecond pulsar, PSR J0437-4715. This pulsar is a very suitable target for such a study because of its small period (5.75 ms), low DM (2.69 pc cm\u207b\u00b3), and high flux density (~ 90 mJy at 1.4 GHz). The initial work for this thesis involved completion and installation of the Fast Pulsar Timing Machine (FPTM) at Parkes observatory, Australia. With a bandwidth of 128 MHz and time resolution of 4 \u00b5s, this machine made a quantum jump in the time of arrival precision for PSR J0437-4715. The precision improved from ~ 2 \u00b5s to ~ 0.2 \u00b5s. In order to further enhance the signal-to-noise ratio achievable with this pulsar and probe the limits of precision pulsar timing, we have subsequently improved the FPTM significantly by doubling its bandwidth, so that it can record the pulsar radio emission over a 256 MHz bandwidth. This required us to double the IF processing hardware in the FPTM and implement numerous software modifications to control the observing apparatus, interface the FPTM with the observatory control computers, as well as process the data to produce final times of arrival.
\r\n\r\nIntegration of just a few minutes with the 64 m Parkes radio telescope yield times of arrival for PSR J0437-4715 with a precision of 100 nanoseconds. The longer term residuals (3 years) show root-mean-square deviations of 500 nanoseconds. This excessively large scatter in the residuals has been traced to inaccurate polarization calibration, and a systematic quadratic trend of ~ 5 \u00b5s in the times of arrival as a function of baseband frequency. The latter phenomenon has been simulated in software and shown to arise from the large dynamic range in the baseband spectrum. Despite the systematic errors, our measurement of the pulsar's astrometric and binary parameters match the best obtained so far with other millisecond pulsars. This has allowed us to measure the pulsar's parallax, and the secular change in the binary's projected semi-major axis due to the system's proper motion. The latter effect restricts the inclination angle of the binary, i < 43\u00b0. The parallax, along with the period derivative and orbital period derivative, enable us to constrain the distance of the pulsar, 162 < d < 205 pc. A stability analysis of the pulsar's time of arrival residuals demonstrates that it matches the long term stability of the best studied millisecond pulsars, PSRs B1937+21 and B1855+09, at least on the time scale of the data available so far, 3 years. The precision in the pulsar position now matches the amplitude of the modulation of position expected from the pulsar's binary motion. Detection of this effect will require reduction of the calibration and spectral shape errors, as well as further refinements in the timing software used. Along with radio interferometric observations of the pulsar and optical detection of the white-dwarf companion, the pulsar timing position will provide the best contraints for frame tie between the ecliptic and extragalactic reference frames.
", "doi": "10.7907/17DD-8X47", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:3444", "collection": "thesis", "collection_id": "3444", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09102008-135630", "primary_object_url": { "basename": "Myers_st_1990.pdf", "content": "final", "filesize": 8686628, "license": "other", "mime_type": "application/pdf", "url": "/3444/1/Myers_st_1990.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "A Search for Anisotropy in the Cosmic Microwave Background on Angular Scales of 1 to 30 Arcminutes", "author": [ { "family_name": "Myers", "given_name": "Steven Theodore", "clpid": "Myers-Steven-Theodore" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Mould", "given_name": "Jeremy R.", "orcid": "0000-0003-3820-1740", "clpid": "Mould-J-R" }, { "family_name": "Sargent", "given_name": "Wallace L. W.", "clpid": "Sargent-W-L-W" }, { "family_name": "Phinney", "given_name": "E. Sterl", "orcid": "0000-0002-9656-4032", "clpid": "Phinney-E-S" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Observations at a frequency of 20 GHz from the Owens Valley Radio Observatory with the 40-meter diameter radiotelescope are used to place limits on the anisotropy of the cosmic microwave background radiation, believed to be a relic from the Big Bang. Two experiments, designated NCP and RING, were performed with the former consisting of deep measurements in 8 fields at the declination \u03b4 = 89\u00b0 and the latter a survey of 96 fields at declination \u03b4 = 88\u00b0 10'42\". Bayesian statistical analysis of the 8 NCP field observations place a 95% confidence upper limit of \u03b4T/T < 1.9 x 10-5 (in fractions of the microwave background temperature 2.735 K) and 4.2 x 10-5 for 99.87% confidence (3\u03c3) on the amplitude of fluctuations with a characteristic correlation length of 2'.6. The 96 fields of the RING experiment were observed in an interlocked ring-like geometry to enhance the sensitivity of the experiment to larger-scale anisotropies. Because of the larger area of sky covered, this data was more susceptible to contamination by discrete extragalactic radio sources and separate lower frequency observations were used to identify and correct for the contributions of these objects. The statistical analysis of the RING data results in the limits on the anisotropy of 2.5 < \u03b4T/T < 5.0 x 10-5 (95%) and 1.9 < \u03b4T/T < 6.1 x 10-5 (99.87%) for fluctuations with a correlation angle of 2'.6. Because of the high probability of residual discrete source contamination, these results are treated as upper limits on intrinsic background fluctuations. These experiments constrain the amplitude to be less than 3 x 10-4 for correlation angles between 0'.1 and 30' (95%). The implications for cosmology and theories of galaxy formation are discussed, and models without significant non-baryonic matter and/or non-standard recombination are excluded by the observations.\r\n", "doi": "10.7907/p4e7-rw11", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:7823", "collection": "thesis", "collection_id": "7823", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06032013-115455313", "primary_object_url": { "basename": "Nakajima_t_1989.pdf", "content": "final", "filesize": 31098962, "license": "other", "mime_type": "application/pdf", "url": "/7823/1/Nakajima_t_1989.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Diffraction-Limited Imaging on the 200-Inch Telescope", "author": [ { "family_name": "Nakajima", "given_name": "Tadashi", "clpid": "Nakajima-Tadashi" } ], "thesis_advisor": [ { "family_name": "Neugebauer", "given_name": "Gerry", "clpid": "Neugebauer-G" } ], "thesis_committee": [ { "family_name": "Neugebauer", "given_name": "Gerry", "clpid": "Neugebauer-G" }, { "family_name": "Frautschi", "given_name": "Steven C.", "clpid": "Frautschi-S-C" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Thorne", "given_name": "Kip S.", "clpid": "Thorne-K-S" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "We have used the technique of non-redundant masking at the Palomar 200-inch telescope and radio VLBI imaging software to make optical aperture synthesis maps of two binary stars, \u03b2 Corona Borealis and \u03c3 Herculis. The dynamic range of the map of \u03b2 CrB, a binary star with a separation of 230 milliarcseconds is 50:1. For \u03c3 Her, we find a separation of 70 milliarcseconds and the dynamic range of our image is 30:1. These demonstrate the potential of the non-redundant masking technique for diffraction-limited imaging of astronomical objects with high dynamic range.
\r\n\r\nWe find that the optimal integration time for measuring the closure phase is longer than that for measuring the fringe amplitude. There is not a close relationship between amplitude errors and phase errors, as is found in radio interferometry. Amplitude self calibration is less effective at optical wavelengths than at radio wavelengths. Primary beam sensitivity correction made in radio aperture synthesis is not necessary in optical aperture synthesis.
\r\n\r\nThe effects of atmospheric disturbances on optical aperture synthesis have been studied by Monte Carlo simulations based on the Kolmogorov theory of refractive-index fluctuations. For the non-redundant masking with \u03c4c-sized apertures, the simulated fringe amplitude gives an upper bound of the observed fringe amplitude. A smooth transition is seen from the non-redundant masking regime to the speckle regime with increasing aperture size. The fractional reduction of the fringe amplitude according to the bandwidth is nearly independent of the aperture size. The limiting magnitude of optical aperture synthesis with \u03c4c-sized apertures and that with apertures larger than \u03c4c are derived.
\r\n\r\nMonte Carlo simulations are also made to study the sensitivity and resolution of the bispectral analysis of speckle interferometry. We present the bispectral modulation transfer function and its signal-to-noise ratio at high light levels. The results confirm the validity of the heuristic interferometric view of image-forming process in the mid-spatial-frequency range. The signal-to-noise ratio of the bispectrum at arbitrary light levels is derived in the mid-spatial-frequency range.
\r\n\r\nThe non-redundant masking technique is suitable for imaging bright objects with high resolution and high dynamic range, while the faintest limit will be better pursued by speckle imaging.
", "doi": "10.7907/hgnx-x451", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:7823", "collection": "thesis", "collection_id": "7823", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06032013-115455313", "primary_object_url": { "basename": "Nakajima_t_1989.pdf", "content": "final", "filesize": 31098962, "license": "other", "mime_type": "application/pdf", "url": "/7823/1/Nakajima_t_1989.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Diffraction-Limited Imaging on the 200-Inch Telescope", "author": [ { "family_name": "Nakajima", "given_name": "Tadashi", "clpid": "Nakajima-Tadashi" } ], "thesis_advisor": [ { "family_name": "Neugebauer", "given_name": "Gerry", "clpid": "Neugebauer-G" } ], "thesis_committee": [ { "family_name": "Neugebauer", "given_name": "Gerry", "clpid": "Neugebauer-G" }, { "family_name": "Frautschi", "given_name": "Steven C.", "clpid": "Frautschi-S-C" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Thorne", "given_name": "Kip S.", "clpid": "Thorne-K-S" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "We have used the technique of non-redundant masking at the Palomar 200-inch telescope and radio VLBI imaging software to make optical aperture synthesis maps of two binary stars, \u03b2 Corona Borealis and \u03c3 Herculis. The dynamic range of the map of \u03b2 CrB, a binary star with a separation of 230 milliarcseconds is 50:1. For \u03c3 Her, we find a separation of 70 milliarcseconds and the dynamic range of our image is 30:1. These demonstrate the potential of the non-redundant masking technique for diffraction-limited imaging of astronomical objects with high dynamic range.
\r\n\r\nWe find that the optimal integration time for measuring the closure phase is longer than that for measuring the fringe amplitude. There is not a close relationship between amplitude errors and phase errors, as is found in radio interferometry. Amplitude self calibration is less effective at optical wavelengths than at radio wavelengths. Primary beam sensitivity correction made in radio aperture synthesis is not necessary in optical aperture synthesis.
\r\n\r\nThe effects of atmospheric disturbances on optical aperture synthesis have been studied by Monte Carlo simulations based on the Kolmogorov theory of refractive-index fluctuations. For the non-redundant masking with \u03c4c-sized apertures, the simulated fringe amplitude gives an upper bound of the observed fringe amplitude. A smooth transition is seen from the non-redundant masking regime to the speckle regime with increasing aperture size. The fractional reduction of the fringe amplitude according to the bandwidth is nearly independent of the aperture size. The limiting magnitude of optical aperture synthesis with \u03c4c-sized apertures and that with apertures larger than \u03c4c are derived.
\r\n\r\nMonte Carlo simulations are also made to study the sensitivity and resolution of the bispectral analysis of speckle interferometry. We present the bispectral modulation transfer function and its signal-to-noise ratio at high light levels. The results confirm the validity of the heuristic interferometric view of image-forming process in the mid-spatial-frequency range. The signal-to-noise ratio of the bispectrum at arbitrary light levels is derived in the mid-spatial-frequency range.
\r\n\r\nThe non-redundant masking technique is suitable for imaging bright objects with high resolution and high dynamic range, while the faintest limit will be better pursued by speckle imaging.
", "doi": "10.7907/hgnx-x451", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:3413", "collection": "thesis", "collection_id": "3413", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09092008-113501", "primary_object_url": { "basename": "Edelson_r_1987.pdf", "content": "final", "filesize": 18973688, "license": "other", "mime_type": "application/pdf", "url": "/3413/1/Edelson_r_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Broadband Properties of Active Galactic Nuclei", "author": [ { "family_name": "Edelson", "given_name": "Richard Allen", "clpid": "Edelson-Richard-Allen" } ], "thesis_advisor": [ { "family_name": "Schmidt", "given_name": "Maarten", "clpid": "Schmidt-M" } ], "thesis_committee": [ { "family_name": "Schmidt", "given_name": "Maarten", "clpid": "Schmidt-M" }, { "family_name": "Moffet", "given_name": "Alan Theodore", "clpid": "Moffet-A-T" }, { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "The broadband radio-infrared-optical-ultraviolet properties of active galactic nuclei are used to investigate the nature of the central engine and the surrounding environment. Optically selected quasars (which have \u03b1̅IR = -1.09; S\u03bd \u221d \u03bd\u03b1) and Seyfert 1 galaxies (\u03b1̅IR = -1.15) tend to have relatively flat infrared spectra and low reddenings, while most Seyfert 2 galaxies (\u03b1̅IR = -1.56) and other dusty objects have steep infrared spectra and larger reddenings. The infrared spectra of most luminous radio-quiet active galaxies turn over near ~80 \u00b5m. It appears that the infrared spectra of most quasars and luminous Seyfert 1 galaxies are dominated by unreprocessed radiation from a synchrotron self-absorbed source of order a light day across, about the size of the hypothesized accretion disk. Seyfert 2 galaxies and other reddened objects have infrared spectra which appear to be dominated by thermal emission from warm (~50 K) dust, probably in the disk of the underlying galaxy. A broad emission feature, centered near 5 \u00b5m, is present in many luminous quasars and Seyfert 1 galaxies.
\r\n\r\nHighly polarized objects (\"blazars\") can be strongly variable at far-infrared wavelengths over time scales of months. There is no conclusive evidence for far-infrared variations in normal (low-polarization) quasars or Seyfert galaxies, although low-level flickering (at the ~30% peak-to-peak level) cannot be ruled out.
\r\n\r\nSeyfert galaxies tend to have steep radio spectra (\u03b1rad \u2248 -0.7). The radio spectra of Seyfert 1 galaxies often flatten out near 2 cm. There is no significant difference in the mean radio luminosities of Seyfert 1 and 2 galaxies. There are of order 105 Seyfert galaxies/Gpc3, most of which have 6 cm luminosities between 1037.0 and 1039.4 ergs/s and 60 \u00b5m luminosities between 1042.2 and 1045.0 ergs/s. The Seyfert 2 galaxy radio luminosity function cuts off sharply below 1037.4 ergs/s.
", "doi": "10.7907/gtk1-3n45", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:3413", "collection": "thesis", "collection_id": "3413", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09092008-113501", "primary_object_url": { "basename": "Edelson_r_1987.pdf", "content": "final", "filesize": 18973688, "license": "other", "mime_type": "application/pdf", "url": "/3413/1/Edelson_r_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Broadband Properties of Active Galactic Nuclei", "author": [ { "family_name": "Edelson", "given_name": "Richard Allen", "clpid": "Edelson-Richard-Allen" } ], "thesis_advisor": [ { "family_name": "Schmidt", "given_name": "Maarten", "clpid": "Schmidt-M" } ], "thesis_committee": [ { "family_name": "Schmidt", "given_name": "Maarten", "clpid": "Schmidt-M" }, { "family_name": "Moffet", "given_name": "Alan Theodore", "clpid": "Moffet-A-T" }, { "family_name": "Scoville", "given_name": "Nicholas Zabriskie", "orcid": "0000-0002-0438-3323", "clpid": "Scoville-N-Z" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "The broadband radio-infrared-optical-ultraviolet properties of active galactic nuclei are used to investigate the nature of the central engine and the surrounding environment. Optically selected quasars (which have \u03b1̅IR = -1.09; S\u03bd \u221d \u03bd\u03b1) and Seyfert 1 galaxies (\u03b1̅IR = -1.15) tend to have relatively flat infrared spectra and low reddenings, while most Seyfert 2 galaxies (\u03b1̅IR = -1.56) and other dusty objects have steep infrared spectra and larger reddenings. The infrared spectra of most luminous radio-quiet active galaxies turn over near ~80 \u00b5m. It appears that the infrared spectra of most quasars and luminous Seyfert 1 galaxies are dominated by unreprocessed radiation from a synchrotron self-absorbed source of order a light day across, about the size of the hypothesized accretion disk. Seyfert 2 galaxies and other reddened objects have infrared spectra which appear to be dominated by thermal emission from warm (~50 K) dust, probably in the disk of the underlying galaxy. A broad emission feature, centered near 5 \u00b5m, is present in many luminous quasars and Seyfert 1 galaxies.
\r\n\r\nHighly polarized objects (\"blazars\") can be strongly variable at far-infrared wavelengths over time scales of months. There is no conclusive evidence for far-infrared variations in normal (low-polarization) quasars or Seyfert galaxies, although low-level flickering (at the ~30% peak-to-peak level) cannot be ruled out.
\r\n\r\nSeyfert galaxies tend to have steep radio spectra (\u03b1rad \u2248 -0.7). The radio spectra of Seyfert 1 galaxies often flatten out near 2 cm. There is no significant difference in the mean radio luminosities of Seyfert 1 and 2 galaxies. There are of order 105 Seyfert galaxies/Gpc3, most of which have 6 cm luminosities between 1037.0 and 1039.4 ergs/s and 60 \u00b5m luminosities between 1042.2 and 1045.0 ergs/s. The Seyfert 2 galaxy radio luminosity function cuts off sharply below 1037.4 ergs/s.
", "doi": "10.7907/gtk1-3n45", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:10448", "collection": "thesis", "collection_id": "10448", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09222017-142706466", "primary_object_url": { "basename": "Romani_RW_1987.pdf", "content": "final", "filesize": 70003746, "license": "other", "mime_type": "application/pdf", "url": "/10448/1/Romani_RW_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Neutron Stars Observations as Astrophysical Probes", "author": [ { "family_name": "Romani", "given_name": "Roger William", "orcid": "0000-0001-6711-3286", "clpid": "Romani-Roger-William" } ], "thesis_advisor": [ { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" } ], "thesis_committee": [ { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "TAPIR" }, { "literal": "div_pma" } ], "abstract": "Several aspects of observations of neutron stars and compact extragalactic radio sources are considered, with particular regard to their use in constraining certain astrophysical phenomena.
\r\n\r\nA theoretical treatment of the pulse arrival time analysis of millisecond pulsars is made; we consider how a detailed timing analysis can be used to quantitatively probe noise processes affecting the pulsar period and the propagation of the radiation. The intrinsic noise may be used to study the neutron star interior, while propagation effects due to gravitational perturbations of the neutron star and interstellar refraction of the emitted radio waves provide probes of the pulsar environment and the intervening plasma. In addition, important constraints on the background of cosmological gravitational radiation can be derived from timing such pulsars.
\r\n\r\nWe consider the thermal X-rays emitted from a warm (105K \u2272 Teff \u2272 3 x 106 K) neutron star, either cooling from its initial formation or heated by internal dissipation, accretion, etc. Constructing model atmospheres appropriate to such stars with various effective temperatures and elemental abundances, we calculate their emergent spectra and the bolometric correction for observation bands of various X-ray satellites. We conclude that the present limits on neutron star surface flux are even more constraining than those derived assuming that the spectra are blackbody and examine how this effects models of neutron star interiors, formation and cooling. We also examine the consequences of similar X-ray observations for neutron star models of various gamma-ray stars.
\r\n\r\nThe refraction of radio waves from pulsars and other compact sources by interstellar plasma is also studied. We show how pulsar observations, in particular, can be used to characterise the large scale inhomogeneities in the ionized ISM and compute a number of observable effects for various electron density perturbation spectra. It is shown how similar refraction can account for the low and intermediate frequency variation of compact extragalactic radio sources. We argue that the observations indicate that more power is present in the large scale fluctuations than previously believed. In addition, single ~1014 cm scale clouds in a previously unrecognized dense, ionised phase of the ISM can apparently dominate the refractive scintillation for some lines of sight.
", "doi": "10.7907/txfg-q107", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:10448", "collection": "thesis", "collection_id": "10448", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09222017-142706466", "primary_object_url": { "basename": "Romani_RW_1987.pdf", "content": "final", "filesize": 70003746, "license": "other", "mime_type": "application/pdf", "url": "/10448/1/Romani_RW_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Neutron Stars Observations as Astrophysical Probes", "author": [ { "family_name": "Romani", "given_name": "Roger William", "orcid": "0000-0001-6711-3286", "clpid": "Romani-Roger-William" } ], "thesis_advisor": [ { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" } ], "thesis_committee": [ { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Goldreich", "given_name": "Peter Martin", "clpid": "Goldreich-P-M" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "TAPIR" }, { "literal": "div_pma" } ], "abstract": "Several aspects of observations of neutron stars and compact extragalactic radio sources are considered, with particular regard to their use in constraining certain astrophysical phenomena.
\r\n\r\nA theoretical treatment of the pulse arrival time analysis of millisecond pulsars is made; we consider how a detailed timing analysis can be used to quantitatively probe noise processes affecting the pulsar period and the propagation of the radiation. The intrinsic noise may be used to study the neutron star interior, while propagation effects due to gravitational perturbations of the neutron star and interstellar refraction of the emitted radio waves provide probes of the pulsar environment and the intervening plasma. In addition, important constraints on the background of cosmological gravitational radiation can be derived from timing such pulsars.
\r\n\r\nWe consider the thermal X-rays emitted from a warm (105K \u2272 Teff \u2272 3 x 106 K) neutron star, either cooling from its initial formation or heated by internal dissipation, accretion, etc. Constructing model atmospheres appropriate to such stars with various effective temperatures and elemental abundances, we calculate their emergent spectra and the bolometric correction for observation bands of various X-ray satellites. We conclude that the present limits on neutron star surface flux are even more constraining than those derived assuming that the spectra are blackbody and examine how this effects models of neutron star interiors, formation and cooling. We also examine the consequences of similar X-ray observations for neutron star models of various gamma-ray stars.
\r\n\r\nThe refraction of radio waves from pulsars and other compact sources by interstellar plasma is also studied. We show how pulsar observations, in particular, can be used to characterise the large scale inhomogeneities in the ionized ISM and compute a number of observable effects for various electron density perturbation spectra. It is shown how similar refraction can account for the low and intermediate frequency variation of compact extragalactic radio sources. We argue that the observations indicate that more power is present in the large scale fluctuations than previously believed. In addition, single ~1014 cm scale clouds in a previously unrecognized dense, ionised phase of the ISM can apparently dominate the refractive scintillation for some lines of sight.
", "doi": "10.7907/txfg-q107", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:3434", "collection": "thesis", "collection_id": "3434", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09102008-091002", "primary_object_url": { "basename": "Hough_dh_1986.pdf", "content": "final", "filesize": 5668667, "license": "other", "mime_type": "application/pdf", "url": "/3434/1/Hough_dh_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Parsec-Scale Structure in the Nuclei of Double-Lobed Radio Quasars", "author": [ { "family_name": "Hough", "given_name": "David Hans", "clpid": "Hough-David-Hans" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Cohen", "given_name": "Marshall H.", "clpid": "Cohen-M-H" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Schmidt", "given_name": "Maarten", "clpid": "Schmidt-M" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "A complete sample of double-lobed quasars is defined, which is believed to be randomly oriented and which contains many objects with central components accessible to very-long-baseline interferometry (VLSI). The purpose of defining the sample in this way is to facilitate tests of physical models proposed to explain both the compact and extended structures in extragalactic radio sources. Statistical studies of the properties of these objects on the >~ kiloparsec scale are consistent with the assumption of random orientations and the simple relativistic beaming theory.
\r\n\r\nThe central components of six double-lobed quasars have been mapped at high resolution and high sensitivity with VLBI. Each object exhibits a double or extended structure on the the ~parsec scale. This structure can be interpreted as a \"core-jet,\" the same morphology found in the dominant cores of powerful flat-spectrum sources, thus indicating a relation between the two classes of compact radio source. The presumed VLBI jets are all fairly well aligned with >~kiloparsec-scale, one-sided jets. The fact that the VLBI and large-scale jets always lie on the same side of the compact core suggests the same cause for the asymmetric structure on both scales.
\r\n\r\nThe central components of 3C245 and 3C263 have been mapped at three epochs. We find superluminal expansion in 3C263 with an apparent velocity of ~1.5c, and argue that there is evidence that 3C245 will also be found to be superluminal. These results are consistent with the simple beaming theory. It is thus clear that we will be able to measure component motion in many of these objects, which will permit us to distinguish among alternative theories of parsec-scale structure and motion.
\r\n\r\nThe future study of these compact central components will benefit greatly from the increased resolution afforded by both higher frequency, ground-based VLBI and VLBI using a radio telescope in Earth orbit.
\r\n", "doi": "10.7907/8P47-SM58", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:3409", "collection": "thesis", "collection_id": "3409", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09092008-093723", "primary_object_url": { "basename": "Simon_rs_1983.pdf", "content": "final", "filesize": 4341639, "license": "other", "mime_type": "application/pdf", "url": "/3409/1/Simon_rs_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Nuclear Structure of Quasars at 329 Megahertz", "author": [ { "family_name": "Simon", "given_name": "Richard Stanley", "clpid": "Simon-Richard-Stanley" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Cohen", "given_name": "Marshall H.", "clpid": "Cohen-M-H" }, { "family_name": "Schmidt", "given_name": "Maarten", "clpid": "Schmidt-M" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "In the four chapters in this thesis are presented studies of compact quasars using Very Long Baseline Interferometry at 329 MHz.
\r\n\r\nThe first chapter presents hybrid maps of two quasars, 3C147 and 3C286, made at 329 MHz from VLBI observations taken in 1975 with a three station interferometer. The observations presented in the first chapter were used to make the first detailed maps of compact radio structure at this frequency. Both objects consist of an unresolved core; an extended, asymmetric jet; and an even larger, completely resolved halo. For 3C147 it is possible to decompose the spectrum into individual component spectra; at 329 MHz the core of 3C147 is found to be strongly self-absorbed. For both sources the spectral index decreases monotonically from core to jet to halo.
\r\n\r\nThe second chapter presents further observations of quasars at 329 MHz. These observations were taken with a seven-station interferometer and were used to produce high dynamic range maps of the quasars 3C48, 3C147, 3C309.1, 3C380, and 3C454.3. These maps, made with the most extensive low-frequency VLBI observations to date, are the first reliable, high dynamic range maps at this frequency, and reveal extremely complex source structure in four of these sources. All five of the objects are seen to have asymmetric structure that can be interpreted in the \"core-jet\" picture of compact extragalactic radio sources. The jets observed in these objects are not straight, but bent; three of these quasars have bends in their structure greater than 90\u00b0 on scales of 1 - 10 kpc.
\r\n\r\nChapter three deals with the analysis of the two maps of 3C147 presented in chapters 1 and 2. Comparison of those maps reveals that the core of 3C147 is a low-frequency variable radio source which has brightened by a factor of two in six years. In combination with X-ray observations this is used to demonstrate that bulk relativistic motion is taking place within the core and leads to the prediction that 3C147 is a member of the class of \"superluminal\" radio sources. It is also found that the inclination to the line of sight of the underlying bulk relativistic motion is less than 10\u00b0.
\r\n\r\nA self-consistent picture of 3C147 as a low-frequency variable is thus developed which is consistent with the available observations, yet does not require an extreme value of the total energy: the total energy of the core of 3C147 is found to be ~1054 ergs. Together with NRAO 140 there are now two extragalactic low-frequency variable radio sources in which bulk relativistic motion has been demonstrated. Thus it may well be that bulk relativistic motion is responsible for the required time-scales in most, if not all, low-frequency variables.
\r\n\r\nIn chapter four, the observations presented in chapter two of 3C48, 3C147, 3C309.1, 3C380 and 3C4S4.3 are analyzed using standard synchrotron emission theory in order to discover the physical conditions occurring in these objects. For 3C48, the suggestion in chapter 2 of this source as a \"core-jet\" source is seen to be reasonable with fields energy density and pressure all decreasing with increasing distance from the supposed core. For 3C48, the suggestion in chapter 2 of this source as a \"core-jet\" source is seen to be reasonable, with fields, energy density, and pressure all decreasing with increasing distance from the supposed core. The pressure in the jet in 3C48 is extremely large, implying that the jet cannot be confined by external gas pressure, unless the surrounding medium has extreme values of the temperature and density. In the case of 3C147 (which was analyzed extensively in chapter 3), the halfwidth of the observed jet implies that collimation of the jet is occurring; the jet in 3C147 is definitely not a \"free\" jet. For 3C309.1, the 329 MHz observations give an upper limit to the turnover frequency for synchrotron self-absorption significantly lower than that available up to now; this limit, in combination with Einstein X-ray observations of 3C309.1, implies that bulk relativistic motion is occurring within the core of 3C309.1. Thus, the core of 3C309.1 may be very similar to the core of 3C147, and is a candidate for being both a superluminal source and a low-frequency variable. For 3C380 and 3C454.3, the limited spectral information available allows broad limits to be put on their properties.
\r\n", "doi": "10.7907/zyfw-8c64", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3391", "collection": "thesis", "collection_id": "3391", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09082008-140704", "primary_object_url": { "basename": "Horne_kd_1983.pdf", "content": "final", "filesize": 2838683, "license": "other", "mime_type": "application/pdf", "url": "/3391/1/Horne_kd_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Eclipse Mapping of Accretion Disks in Cataclysmic Binaries", "author": [ { "family_name": "Horne", "given_name": "Keith Douglas", "orcid": "0000-0003-1728-0304", "clpid": "Horne-Keith-Douglas" } ], "thesis_advisor": [ { "family_name": "Oke", "given_name": "J. Beverley", "clpid": "Oke-J-B" } ], "thesis_committee": [ { "family_name": "Oke", "given_name": "J. Beverly", "clpid": "Oke-J-B" }, { "family_name": "Greenstein", "given_name": "Jesse L.", "clpid": "Greenstein-J-L" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Surface brightness distributions for accretion disks in eclipsing cataclysmic binaries may be reconstructed from observed eclipse light curves by use maximum entropy imaging methods. Three-color eclipse photometry of six eclipsing cataclysmic binaries provides the basis for an observational study of the local and global structure of their accretion disks. Observations from several eclipse cycles are averaged to form mean eclipse profiles with diminished contamination by flickering. Flickering is shown to be widely distributed over the face of the accretion disks in RW Tri and LX Ser. Accretion disk maps are derived which give satisfying fits to the observed eclipse profiles and which are maximally symmetric about the center of the disk. Disk maps for nova DQ Her and for four nova-like systems show broad intensity distributions with bright spots, associated with the gas streams that feed the disks, in evidence at a radii comparable to the disk tidal radius. The HT Cas disk is smaller and is dominated by a compact source at its center. Analysis of disk intensity maps at U, B and R show that the brighter parts of the accretion disks are optically-thick thermal radiators with temperatures which decrease with radius. The angular scale of each disk is fixed by a method analogous to cluster main sequence fitting. Distance estimates are derived which are free of assumptions about the global structure of the disks, but which depend on currently uncertain dyamical parameters of the binaries. The temperature in the disk is observed to fall much more slowly with radius than the R-3/4 law predicted by a steady-state mass-conserving viscous accretion disk model. Apparently, much of the visible light from the disk is produced by reprocessing of hard radiation from the center of the disk. Upper limits are found for the mass transfer rates which are one to two orders of magnitude smaller than the canonical mass transfer rate for novae and nova-like systems and which thus are in better agreement with mass transfer driven by gravitational radiation alone. Mass transfer rates have previously been systematically overestimated by the neglect of reprocessing. The accretion disk in HT Cas is shown to be optically thin in the Paschen continuum. The compact bright source at the center of its disk is a composite of light from the photosphere of the white dwarf and of free-free emission from hot gas in the accretion boundary layer.
\r\n", "doi": "10.7907/5E49-4N30", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3436", "collection": "thesis", "collection_id": "3436", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09102008-091935", "primary_object_url": { "basename": "Malkan_ma_1983.pdf", "content": "final", "filesize": 6482387, "license": "other", "mime_type": "application/pdf", "url": "/3436/1/Malkan_ma_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Physical Nature of the Continuum in Active Galaxies", "author": [ { "family_name": "Malkan", "given_name": "Matthew Arnold", "orcid": "0000-0001-6919-1237", "clpid": "Malkan-Matthew-Arnold" } ], "thesis_advisor": [ { "family_name": "Sargent", "given_name": "Wallace L. W.", "clpid": "Sargent-W-L-W" } ], "thesis_committee": [ { "family_name": "Oke", "given_name": "J. Beverly", "clpid": "Oke-J-B" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Sargent", "given_name": "Wallace L. W.", "clpid": "Sargent-W-L-W" }, { "family_name": "Schmidt", "given_name": "Maarten", "clpid": "Schmidt-M" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "We have measured the intrinsic nonstellar continuum from the nuclei of a wide range of active galaxies. We find little or no continuum reddening (from the 2175\u00c5 absorption bump) above that expected from the interstellar medium of the Milky Way. Nor do optical and ultraviolet emission from permitted Fe II lines alter the overall appearance of the energy distribution very much. After accounting for hydrogen recombination radiation, we find the continuum consists of a power law (fV\u221dV-1.1), closely related to the X-ray emission, and an optically thick thermal component. Some bright quasars produce as much or more thermal power as nonthermal. The thermal energy has an average characteristic temperature of 20-30,000 K. It is perfectly described by relativistic accretion disk models which include the gravitational redshifting and focusing of emerging light. These models are completely specified by two well-determined parameters: the mass of the central black hole and the accretion rate. The hole masses range from 0.2-0.5 billion M\u2609 in 3C 273 to 1-3 billion in the most luminous quasars, depending on the disk inclination and the angular momentum of the hole. All the bright quasars are shining at within a factor of two of their Eddington limits, while the Seyfert 1 galaxies are well below theirs.
\r\n\r\nUnlike most Seyfert 1 galaxies, those of type 2 have a large portion of their total power re-radiated in the infrared by warm dust grains. The intrinsic continuum in the Seyfert 2 galaxies may have a nonthermal power-law, but appears to lack the hot thermal component seen in quasars. The host galaxies around Seyfert nuclei of types 1 and 2, and those around low-redshift quasars are normal spirals of early to intermediate type.
\r\n\r\nWe calculated the level populations for the 0+ and S+ ions, to use the [0 II] (7320+7330)/(3726+3729) and [S II] (4069+4076)/(6716+6730) line ratios as reddening indicators (accurate to \u00b10.1 mag. in EB-V). Seyfert 2 galaxies are typically reddened by 0.2-0.5 mag. Most Seyfert 1 galaxies have less than half as much reddening. The H\u03b1/H\u03b2 ratio in the broad-line region is often much larger than the Case B value, and it is significantly larger than 2.86 in some narrow-line regions. The intrinsic Balmer continuum/H\u03b1 ratio in the narrow-line region is 1.4, consistent with the Case B prediction. But in the broad-line region it is two to three times larger, because of the effects of high electron density and optical depth.
", "doi": "10.7907/Z85C-9706", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3436", "collection": "thesis", "collection_id": "3436", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09102008-091935", "primary_object_url": { "basename": "Malkan_ma_1983.pdf", "content": "final", "filesize": 6482387, "license": "other", "mime_type": "application/pdf", "url": "/3436/1/Malkan_ma_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The Physical Nature of the Continuum in Active Galaxies", "author": [ { "family_name": "Malkan", "given_name": "Matthew Arnold", "orcid": "0000-0001-6919-1237", "clpid": "Malkan-Matthew-Arnold" } ], "thesis_advisor": [ { "family_name": "Sargent", "given_name": "Wallace L. W.", "clpid": "Sargent-W-L-W" } ], "thesis_committee": [ { "family_name": "Oke", "given_name": "J. Beverly", "clpid": "Oke-J-B" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Sargent", "given_name": "Wallace L. W.", "clpid": "Sargent-W-L-W" }, { "family_name": "Schmidt", "given_name": "Maarten", "clpid": "Schmidt-M" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "We have measured the intrinsic nonstellar continuum from the nuclei of a wide range of active galaxies. We find little or no continuum reddening (from the 2175\u00c5 absorption bump) above that expected from the interstellar medium of the Milky Way. Nor do optical and ultraviolet emission from permitted Fe II lines alter the overall appearance of the energy distribution very much. After accounting for hydrogen recombination radiation, we find the continuum consists of a power law (fV\u221dV-1.1), closely related to the X-ray emission, and an optically thick thermal component. Some bright quasars produce as much or more thermal power as nonthermal. The thermal energy has an average characteristic temperature of 20-30,000 K. It is perfectly described by relativistic accretion disk models which include the gravitational redshifting and focusing of emerging light. These models are completely specified by two well-determined parameters: the mass of the central black hole and the accretion rate. The hole masses range from 0.2-0.5 billion M\u2609 in 3C 273 to 1-3 billion in the most luminous quasars, depending on the disk inclination and the angular momentum of the hole. All the bright quasars are shining at within a factor of two of their Eddington limits, while the Seyfert 1 galaxies are well below theirs.
\r\n\r\nUnlike most Seyfert 1 galaxies, those of type 2 have a large portion of their total power re-radiated in the infrared by warm dust grains. The intrinsic continuum in the Seyfert 2 galaxies may have a nonthermal power-law, but appears to lack the hot thermal component seen in quasars. The host galaxies around Seyfert nuclei of types 1 and 2, and those around low-redshift quasars are normal spirals of early to intermediate type.
\r\n\r\nWe calculated the level populations for the 0+ and S+ ions, to use the [0 II] (7320+7330)/(3726+3729) and [S II] (4069+4076)/(6716+6730) line ratios as reddening indicators (accurate to \u00b10.1 mag. in EB-V). Seyfert 2 galaxies are typically reddened by 0.2-0.5 mag. Most Seyfert 1 galaxies have less than half as much reddening. The H\u03b1/H\u03b2 ratio in the broad-line region is often much larger than the Case B value, and it is significantly larger than 2.86 in some narrow-line regions. The intrinsic Balmer continuum/H\u03b1 ratio in the narrow-line region is 1.4, consistent with the Case B prediction. But in the broad-line region it is two to three times larger, because of the effects of high electron density and optical depth.
", "doi": "10.7907/Z85C-9706", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3409", "collection": "thesis", "collection_id": "3409", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09092008-093723", "primary_object_url": { "basename": "Simon_rs_1983.pdf", "content": "final", "filesize": 4341639, "license": "other", "mime_type": "application/pdf", "url": "/3409/1/Simon_rs_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Nuclear Structure of Quasars at 329 Megahertz", "author": [ { "family_name": "Simon", "given_name": "Richard Stanley", "clpid": "Simon-Richard-Stanley" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "thesis_committee": [ { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Cohen", "given_name": "Marshall H.", "clpid": "Cohen-M-H" }, { "family_name": "Schmidt", "given_name": "Maarten", "clpid": "Schmidt-M" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "In the four chapters in this thesis are presented studies of compact quasars using Very Long Baseline Interferometry at 329 MHz.
\r\n\r\nThe first chapter presents hybrid maps of two quasars, 3C147 and 3C286, made at 329 MHz from VLBI observations taken in 1975 with a three station interferometer. The observations presented in the first chapter were used to make the first detailed maps of compact radio structure at this frequency. Both objects consist of an unresolved core; an extended, asymmetric jet; and an even larger, completely resolved halo. For 3C147 it is possible to decompose the spectrum into individual component spectra; at 329 MHz the core of 3C147 is found to be strongly self-absorbed. For both sources the spectral index decreases monotonically from core to jet to halo.
\r\n\r\nThe second chapter presents further observations of quasars at 329 MHz. These observations were taken with a seven-station interferometer and were used to produce high dynamic range maps of the quasars 3C48, 3C147, 3C309.1, 3C380, and 3C454.3. These maps, made with the most extensive low-frequency VLBI observations to date, are the first reliable, high dynamic range maps at this frequency, and reveal extremely complex source structure in four of these sources. All five of the objects are seen to have asymmetric structure that can be interpreted in the \"core-jet\" picture of compact extragalactic radio sources. The jets observed in these objects are not straight, but bent; three of these quasars have bends in their structure greater than 90\u00b0 on scales of 1 - 10 kpc.
\r\n\r\nChapter three deals with the analysis of the two maps of 3C147 presented in chapters 1 and 2. Comparison of those maps reveals that the core of 3C147 is a low-frequency variable radio source which has brightened by a factor of two in six years. In combination with X-ray observations this is used to demonstrate that bulk relativistic motion is taking place within the core and leads to the prediction that 3C147 is a member of the class of \"superluminal\" radio sources. It is also found that the inclination to the line of sight of the underlying bulk relativistic motion is less than 10\u00b0.
\r\n\r\nA self-consistent picture of 3C147 as a low-frequency variable is thus developed which is consistent with the available observations, yet does not require an extreme value of the total energy: the total energy of the core of 3C147 is found to be ~1054 ergs. Together with NRAO 140 there are now two extragalactic low-frequency variable radio sources in which bulk relativistic motion has been demonstrated. Thus it may well be that bulk relativistic motion is responsible for the required time-scales in most, if not all, low-frequency variables.
\r\n\r\nIn chapter four, the observations presented in chapter two of 3C48, 3C147, 3C309.1, 3C380 and 3C4S4.3 are analyzed using standard synchrotron emission theory in order to discover the physical conditions occurring in these objects. For 3C48, the suggestion in chapter 2 of this source as a \"core-jet\" source is seen to be reasonable with fields energy density and pressure all decreasing with increasing distance from the supposed core. For 3C48, the suggestion in chapter 2 of this source as a \"core-jet\" source is seen to be reasonable, with fields, energy density, and pressure all decreasing with increasing distance from the supposed core. The pressure in the jet in 3C48 is extremely large, implying that the jet cannot be confined by external gas pressure, unless the surrounding medium has extreme values of the temperature and density. In the case of 3C147 (which was analyzed extensively in chapter 3), the halfwidth of the observed jet implies that collimation of the jet is occurring; the jet in 3C147 is definitely not a \"free\" jet. For 3C309.1, the 329 MHz observations give an upper limit to the turnover frequency for synchrotron self-absorption significantly lower than that available up to now; this limit, in combination with Einstein X-ray observations of 3C309.1, implies that bulk relativistic motion is occurring within the core of 3C309.1. Thus, the core of 3C309.1 may be very similar to the core of 3C147, and is a candidate for being both a superluminal source and a low-frequency variable. For 3C380 and 3C454.3, the limited spectral information available allows broad limits to be put on their properties.
\r\n", "doi": "10.7907/zyfw-8c64", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3391", "collection": "thesis", "collection_id": "3391", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09082008-140704", "primary_object_url": { "basename": "Horne_kd_1983.pdf", "content": "final", "filesize": 2838683, "license": "other", "mime_type": "application/pdf", "url": "/3391/1/Horne_kd_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Eclipse Mapping of Accretion Disks in Cataclysmic Binaries", "author": [ { "family_name": "Horne", "given_name": "Keith Douglas", "orcid": "0000-0003-1728-0304", "clpid": "Horne-Keith-Douglas" } ], "thesis_advisor": [ { "family_name": "Oke", "given_name": "J. Beverley", "clpid": "Oke-J-B" } ], "thesis_committee": [ { "family_name": "Oke", "given_name": "J. Beverly", "clpid": "Oke-J-B" }, { "family_name": "Greenstein", "given_name": "Jesse L.", "clpid": "Greenstein-J-L" }, { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Surface brightness distributions for accretion disks in eclipsing cataclysmic binaries may be reconstructed from observed eclipse light curves by use maximum entropy imaging methods. Three-color eclipse photometry of six eclipsing cataclysmic binaries provides the basis for an observational study of the local and global structure of their accretion disks. Observations from several eclipse cycles are averaged to form mean eclipse profiles with diminished contamination by flickering. Flickering is shown to be widely distributed over the face of the accretion disks in RW Tri and LX Ser. Accretion disk maps are derived which give satisfying fits to the observed eclipse profiles and which are maximally symmetric about the center of the disk. Disk maps for nova DQ Her and for four nova-like systems show broad intensity distributions with bright spots, associated with the gas streams that feed the disks, in evidence at a radii comparable to the disk tidal radius. The HT Cas disk is smaller and is dominated by a compact source at its center. Analysis of disk intensity maps at U, B and R show that the brighter parts of the accretion disks are optically-thick thermal radiators with temperatures which decrease with radius. The angular scale of each disk is fixed by a method analogous to cluster main sequence fitting. Distance estimates are derived which are free of assumptions about the global structure of the disks, but which depend on currently uncertain dyamical parameters of the binaries. The temperature in the disk is observed to fall much more slowly with radius than the R-3/4 law predicted by a steady-state mass-conserving viscous accretion disk model. Apparently, much of the visible light from the disk is produced by reprocessing of hard radiation from the center of the disk. Upper limits are found for the mass transfer rates which are one to two orders of magnitude smaller than the canonical mass transfer rate for novae and nova-like systems and which thus are in better agreement with mass transfer driven by gravitational radiation alone. Mass transfer rates have previously been systematically overestimated by the neglect of reprocessing. The accretion disk in HT Cas is shown to be optically thin in the Paschen continuum. The compact bright source at the center of its disk is a composite of light from the photosphere of the white dwarf and of free-free emission from hot gas in the accretion boundary layer.
\r\n", "doi": "10.7907/5E49-4N30", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3317", "collection": "thesis", "collection_id": "3317", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09022008-153247", "type": "thesis", "title": "Studies of Compact Extragalactic Radio Sources", "author": [ { "family_name": "Linfield", "given_name": "Roger Paul", "clpid": "Linfield-Roger-Paul" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Hall", "given_name": "Marshall", "clpid": "Hall-M" } ], "thesis_committee": [ { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Kellerman", "given_name": "Kenneth I.", "clpid": "Kellerman-Kenneth-I" }, { "family_name": "Young", "given_name": "Peter J.", "clpid": "Young-Peter-J" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "TAPIR" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Three studies of compact, extragalactic radio sources are presented.
\r\n\r\nIn the first, VLBI maps are presented of the nuclear cores of four radio galaxies which have large symmetric radio lobes: 3C 111, 3C 390.3, Cyg A, and 0055+30. Each source contains a nuclear jet having a scale of 1 pc, but no counterjets are seen. The jets in 3C 111 and 0055+30 point directly at the outer radio lobes, but in 3C 390.3 and Cyg A the jets are pointed from 4 to 6 degrees away from the lobes.
\r\n\r\nThe implications of the maps and models of these sources are considered in the second study. It is concluded that in all four cases, the observed asymmetry reflects an intrinsic asymmetry on a msec scale. The minimum pressure in the four jets is calculated, and it is concluded that the jet in Cyg A is very unlikely to be confined by gas pressure.
\r\n\r\nIn the third study, an attempt is made to explain the structure of compact radio sources with a precession-like motion or a relativistic jet. It is found that the curvature of these sources can be readily explained in this way. In addition, the knots which are often revealed by VLBI observations arise naturally in such a model. The main problem with the model is that it cannot by itself explain the arcsecond structure of asymmetric radio sources.
", "doi": "10.7907/5cg5-0d24", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:3317", "collection": "thesis", "collection_id": "3317", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09022008-153247", "type": "thesis", "title": "Studies of Compact Extragalactic Radio Sources", "author": [ { "family_name": "Linfield", "given_name": "Roger Paul", "clpid": "Linfield-Roger-Paul" } ], "thesis_advisor": [ { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Hall", "given_name": "Marshall", "clpid": "Hall-M" } ], "thesis_committee": [ { "family_name": "Blandford", "given_name": "Roger D.", "clpid": "Blandford-R-D" }, { "family_name": "Kellerman", "given_name": "Kenneth I.", "clpid": "Kellerman-Kenneth-I" }, { "family_name": "Young", "given_name": "Peter J.", "clpid": "Young-Peter-J" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "local_group": [ { "literal": "Owens Valley Radio Observatory (OVRO)" }, { "literal": "TAPIR" }, { "literal": "Astronomy Department" }, { "literal": "div_pma" } ], "abstract": "Three studies of compact, extragalactic radio sources are presented.
\r\n\r\nIn the first, VLBI maps are presented of the nuclear cores of four radio galaxies which have large symmetric radio lobes: 3C 111, 3C 390.3, Cyg A, and 0055+30. Each source contains a nuclear jet having a scale of 1 pc, but no counterjets are seen. The jets in 3C 111 and 0055+30 point directly at the outer radio lobes, but in 3C 390.3 and Cyg A the jets are pointed from 4 to 6 degrees away from the lobes.
\r\n\r\nThe implications of the maps and models of these sources are considered in the second study. It is concluded that in all four cases, the observed asymmetry reflects an intrinsic asymmetry on a msec scale. The minimum pressure in the four jets is calculated, and it is concluded that the jet in Cyg A is very unlikely to be confined by gas pressure.
\r\n\r\nIn the third study, an attempt is made to explain the structure of compact radio sources with a precession-like motion or a relativistic jet. It is found that the curvature of these sources can be readily explained in this way. In addition, the knots which are often revealed by VLBI observations arise naturally in such a model. The main problem with the model is that it cannot by itself explain the arcsecond structure of asymmetric radio sources.
", "doi": "10.7907/5cg5-0d24", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" } ]