ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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Description
Galaxies represent a fundamental catalyst in the ``lifecycle'' of matter in the Universe, and the study of galaxy assembly and evolution provides unique insight into the physical processes governing the transformation of matter from atoms to gas to stars. With the Hubble Space Telescope, the astrophysical community is able to study the formation and evolution of galaxies, at an unrivaled spatial resolution, over more than 90% of cosmic time. Here, I present results from two complementary studies of galaxy evolution in the local and intermediate redshift Universe which used new and archival HST images. First, I use archival broad-band HST WFPC2 optical images of local (d<63 Mpc) Seyfert-type galaxies to test the observed correlation between visually-classified host galaxy dust morphology and AGN class. Using quantitative parameters for classifying galaxy morphology, I do not measure a strong correlation between the galaxy morphology and AGN class. This result could imply that the Unified Model of AGN provides a sufficient model for the observed diversity of AGN, but this result could also indicate the quantitative techniques are insufficient for characterizing the dust morphology of local galaxies. To address the latter, I develop a new automated method using an inverse unsharp masking technique coupled to Source Extractor to detect and measure dust morphology. I measure no strong trends with dust-morphology and AGN class using this method, and conclude that the Unified Model remains sufficient to explain the diversity of AGN. Second, I use new UV-optical-near IR broad-band images obtained with the HST WFC3 in the Early Release Science (ERS) program to study the evolution of massive, early-type galaxies. These galaxies were once considered to be ``red and dead'', as a class uniformly devoid of recent star formation, but observations of these galaxies in the local Universe at UV wavelengths have revealed a significant fraction (30%) of ETGs to have recently formed a small fraction (5-10%) of their stellar mass in young stars. I extend the study of recent star formation in ETGs to intermediate-redshift 0.35<1.5 with the ERS data. Comparing the mass fraction and age of young stellar populations identified in these ETGs from two-component SED analysis with the morphology of the ETG and the frequency of companions, I find that at this redshift many ETGs are likely to have experienced a minor burst of recent star formation. The mechanisms driving this recent star formation are varied, and evidence for both minor merger driven recent star formation as well as the evolution of transitioning ETGs is identified.
ContributorsRutkowski, Michael (Author) / Windhorst, Rogier A. (Thesis advisor) / Bowman, Judd (Committee member) / Butler, Nathaniel (Committee member) / Desch, Steven (Committee member) / Young, Patrick (Committee member) / Arizona State University (Publisher)
Created2013
Description
The Milky Way galaxy is a powerful dynamic system that is highly efficient at recycling material. Stars are born out of intergalactic gas and dust, fuse light elements into heavier elements in their cores, then upon stellar death spread material throughout the galaxy, either by diffusion of planetary nebula or by explosive events for high mass stars, and that gas must cool and condense to form stellar nurseries. Though the stellar lifecycle has been studied in detail, relatively little is known about the processes by which hot, diffuse gas ejected by dying stars cools and conglomerates in the interstellar medium (ISM). Much of this mystery arises because only recently have instruments with sufficient spatial and spectral resolution, sensitivity, and bandwidth become available in the terahertz (THz) frequency spectrum where these clouds peak in either thermal or line emission. In this dissertation, I will demonstrate technology advancement of instruments in this frequency regime with new characterization techniques, machining strategies, and scientific models of the spectral behavior of gas species targeted by these instruments.
I begin this work with a description of radiation pattern measurements and their use in astronomical instrument characterization. I will introduce a novel technique to measure complex (phase-sensitive) field patterns using direct detectors. I successfully demonstrate the technique with a single pixel microwave inductance detectors (MKID) experiment. I expand that work by measuring the APEX MKID (A-MKID) focal plane array of 880 pixel detectors centered at 350 GHz. In both chapters I discuss the development of an analysis pipeline to take advantage of all information provided by complex field mapping. I then discuss the design, simulation, fabrication processes, and characterization of a circular-to-rectangular waveguide transformer module integrated into a circularly symmetric feedhorn block. I conclude with a summary of this work and how to advance these technologies for future ISM studies.
I begin this work with a description of radiation pattern measurements and their use in astronomical instrument characterization. I will introduce a novel technique to measure complex (phase-sensitive) field patterns using direct detectors. I successfully demonstrate the technique with a single pixel microwave inductance detectors (MKID) experiment. I expand that work by measuring the APEX MKID (A-MKID) focal plane array of 880 pixel detectors centered at 350 GHz. In both chapters I discuss the development of an analysis pipeline to take advantage of all information provided by complex field mapping. I then discuss the design, simulation, fabrication processes, and characterization of a circular-to-rectangular waveguide transformer module integrated into a circularly symmetric feedhorn block. I conclude with a summary of this work and how to advance these technologies for future ISM studies.
ContributorsDavis, Kristina (Author) / Groppi, Christopher E (Thesis advisor) / Bowman, Judd (Committee member) / Mauskopf, Philip (Committee member) / Jellema, Willem (Committee member) / Pan, George (Committee member) / Trichopoulos, Georgios (Committee member) / Arizona State University (Publisher)
Created2018
Description
This thesis contains an overview, as well as the history of optical interferometers. A new approach to interferometric measurements of stars is proposed and explored. Modern updates to the classic techniques are described along with some theoretical derivations showing why the method of single photon counting shows significant promise relative to the currently used amplitude interferometry.
Description of a modular intensity interferometer system using commercially available single-photon detectors is given. Calculations on the sensitivity and \emph{uv}-plane coverage using these modules mounted on existing telescopes on Kitt Peak, Arizona is presented.
Determining fundamental stellar properties is essential for testing models of stellar evolution as well as for deriving physical properties of transiting exoplanets. The proposed method shows great promise in measuring the angular size of stars. Simulations indicate that it is possible to measure stellar diameters of bright stars with AB magnitude <6 with a precision of >5% in a single night of observation.
Additionally, a description is given of a custom time-to-digital converter designed to time tag individual photons from multiple single-photon detectors with high count rate, continuous data logging, and low systematics. The instrument utilizes a tapped-delay line approach on an FPGA chip which allows for sub-clock resolution of <100 ps. The TDC is implemented on a Re-configurable Open Architecture Computing Hardware Revision 2 (ROACH2) board which allows for continuous data streaming and time tagging of up to 20 million events per second. The functioning prototype is currently set-up to work with up to ten independent channels. Laboratory characterization of the system, including RF, pick up and mitigation, as well as measurement of in-lab photon correlations from an incoherent light source (artificial star), are presented. Additional improvements to the TDC will also be discussed, such as improving the data transfer rate by a factor of 10 via an SDP+ Mezzanine card and PCIe 2SFP+ 10 Gb card, as well as scaling to 64 independent channels.
Furthermore, a modified nulling interferometer with image inversion is proposed, for direct imaging of exoplanets below the canonical Rayleigh resolution limit. Image inversion interferometry relies on splitting incoming radiation from a source, either spatially rotating or reflecting the electric field from one arm of the interferometer before recombining the signals and detecting the resulting images in the two output ports with an array of high-speed single-photon detectors. Sources of incoming radiation that have cylindrical symmetry and are centered on the rotation axis will cancel in one of the output ports and add in the other output port. The ability to suppress light from a host star, as well as the ability to resolve past the Rayleigh limit, enables sensitive detection of exoplanets from a stable environment without the need for a coronagraph. The expected number of photons and the corresponding variance in the measurement for different initial contrast ratios are shown, with some first-order theoretical instrumental errors.
Lastly, preliminary results from a sizeable photometric survey are presented. This survey is used to derive bolometric flux alongside from angular size measurements and the effective stellar temperatures.
Description of a modular intensity interferometer system using commercially available single-photon detectors is given. Calculations on the sensitivity and \emph{uv}-plane coverage using these modules mounted on existing telescopes on Kitt Peak, Arizona is presented.
Determining fundamental stellar properties is essential for testing models of stellar evolution as well as for deriving physical properties of transiting exoplanets. The proposed method shows great promise in measuring the angular size of stars. Simulations indicate that it is possible to measure stellar diameters of bright stars with AB magnitude <6 with a precision of >5% in a single night of observation.
Additionally, a description is given of a custom time-to-digital converter designed to time tag individual photons from multiple single-photon detectors with high count rate, continuous data logging, and low systematics. The instrument utilizes a tapped-delay line approach on an FPGA chip which allows for sub-clock resolution of <100 ps. The TDC is implemented on a Re-configurable Open Architecture Computing Hardware Revision 2 (ROACH2) board which allows for continuous data streaming and time tagging of up to 20 million events per second. The functioning prototype is currently set-up to work with up to ten independent channels. Laboratory characterization of the system, including RF, pick up and mitigation, as well as measurement of in-lab photon correlations from an incoherent light source (artificial star), are presented. Additional improvements to the TDC will also be discussed, such as improving the data transfer rate by a factor of 10 via an SDP+ Mezzanine card and PCIe 2SFP+ 10 Gb card, as well as scaling to 64 independent channels.
Furthermore, a modified nulling interferometer with image inversion is proposed, for direct imaging of exoplanets below the canonical Rayleigh resolution limit. Image inversion interferometry relies on splitting incoming radiation from a source, either spatially rotating or reflecting the electric field from one arm of the interferometer before recombining the signals and detecting the resulting images in the two output ports with an array of high-speed single-photon detectors. Sources of incoming radiation that have cylindrical symmetry and are centered on the rotation axis will cancel in one of the output ports and add in the other output port. The ability to suppress light from a host star, as well as the ability to resolve past the Rayleigh limit, enables sensitive detection of exoplanets from a stable environment without the need for a coronagraph. The expected number of photons and the corresponding variance in the measurement for different initial contrast ratios are shown, with some first-order theoretical instrumental errors.
Lastly, preliminary results from a sizeable photometric survey are presented. This survey is used to derive bolometric flux alongside from angular size measurements and the effective stellar temperatures.
ContributorsPilyavsky, Genady (Author) / Mauskopf, Philip (Thesis advisor) / Groppi, Christopher (Committee member) / Butler, Nathaniel (Committee member) / Bowman, Judd (Committee member) / Scowen, Paul (Committee member) / Arizona State University (Publisher)
Created2018
Description
The lowest-mass stars, known as M-dwarfs, form target samples for upcoming exoplanet searches, and together with lower-mass substellar objects known as brown dwarfs, are among prime targets for detailed study with high-contrast adaptive optics (AO) imaging and sub-millimeter interferometry. In this thesis, I describe results from three studies investigating the companion properties and environments of low-mass systems: (1) The 245-star M-dwarfs in Multiples (MinMs) Survey, a volume-limited survey of field M-dwarf companions within 15 pc, (2) the Taurus Boundary of Stellar/Substellar (TBOSS) Survey, an ongoing study of disk properties for low-mass members within the Taurus star-forming region, and (3) spectroscopy of a brown dwarf companion using the Gemini Planet Imager (GPI).
Direct imaging of M-dwarfs is a sensitive technique to identify low-mass companions over a wide range of orbital separation, and the high proper motion of nearby M-dwarfs eases confirmation of new multiple stars. Combining AO and wide-field imaging, the MinMs Survey provides new measurements of the companion star fraction (CSF), separation distribution, and mass ratio distribution for the nearest K7-M6 dwarfs. These results demonstrate the closer orbital separations (~6 AU) and lower frequency (~23% CSF) of M-dwarf binaries relative to higher-mass stars.
From the TBOSS project, I report 885µm Atacama Large Millimeter/sub-millimeter Array continuum measurements for 24 Taurus members spanning the stellar/substellar boundary (M4-M7.75). Observations of submillimeter emission from dust grains around the lowest-mass hosts show decreasing disk dust mass for decreasing host star mass, consistent with low frequencies of giant planets around M-dwarfs. Compared to the older stellar association of Upper Scorpius, Taurus disks have a factor of four higher mass in submillimeter-sized grains.
From the GPI Exoplanet Survey, I describe near-infrared spectroscopy of an unusually red companion orbiting inside the debris disk of an F5V star. As the second brown dwarf discovered within the innermost region of a debris disk, the properties of this system offer important dynamical constraints for companion-disk interaction and a useful benchmark for brown dwarf and giant planet atmospheric study.
Direct imaging of M-dwarfs is a sensitive technique to identify low-mass companions over a wide range of orbital separation, and the high proper motion of nearby M-dwarfs eases confirmation of new multiple stars. Combining AO and wide-field imaging, the MinMs Survey provides new measurements of the companion star fraction (CSF), separation distribution, and mass ratio distribution for the nearest K7-M6 dwarfs. These results demonstrate the closer orbital separations (~6 AU) and lower frequency (~23% CSF) of M-dwarf binaries relative to higher-mass stars.
From the TBOSS project, I report 885µm Atacama Large Millimeter/sub-millimeter Array continuum measurements for 24 Taurus members spanning the stellar/substellar boundary (M4-M7.75). Observations of submillimeter emission from dust grains around the lowest-mass hosts show decreasing disk dust mass for decreasing host star mass, consistent with low frequencies of giant planets around M-dwarfs. Compared to the older stellar association of Upper Scorpius, Taurus disks have a factor of four higher mass in submillimeter-sized grains.
From the GPI Exoplanet Survey, I describe near-infrared spectroscopy of an unusually red companion orbiting inside the debris disk of an F5V star. As the second brown dwarf discovered within the innermost region of a debris disk, the properties of this system offer important dynamical constraints for companion-disk interaction and a useful benchmark for brown dwarf and giant planet atmospheric study.
ContributorsWard-Duong, Kimberly Dolan (Author) / Patience, Jennifer (Thesis advisor) / Young, Patrick (Committee member) / Butler, Nathaniel (Committee member) / Bowman, Judd (Committee member) / Groppi, Christopher (Committee member) / Arizona State University (Publisher)
Created2017
Description
Galaxy formation is a complex process with aspects that are still very uncertain or unknown. A mechanism that has been utilized in simulations to successfully resolve several of these outstanding issues is active galactic nucleus (AGN) feedback. Recent work has shown that a promising method for directly measuring this energy is by looking at small increases in the energy of cosmic microwave background (CMB) photons as they pass through ionized gas, known as the thermal Sunyaev-Zel’dovich (tSZ) effect.
In this work, I present stacked CMB measurements of a large number of elliptical galaxies never before measured using this method. I split the galaxies into two redshift groups, "low-z" for z=0.5-1.0 and “high-z” for z=1.0-1.5. I make two independent sets of CMB measurements using data from the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT), respectively, and I use data from the Planck telescope to account for contamination from dust emission. With SPT I find average thermal energies of 7.6(+3.0/−2.3) × 10^60 erg for 937 low-z galaxies, and 6.0(+7.7/−6.3) × 10^60 erg for 240 high-z galaxies. With ACT I find average thermal energies of 5.6(+5.9/−5.6) × 10^60 erg for 227 low-z galaxies, and 7.0(+4.7/−4.4) × 10^60 erg for 529 high-z galaxies.
I then attempt to further interpret the physical meaning of my observational results by incorporating two large-scale cosmological hydrodynamical simulations, one with (Horizon-AGN) and one without (Horizon-NoAGN) AGN feedback. I extract simulated tSZ measurements around a population of galaxies equivalent to those used in my observational work, with matching mass distributions, and compare the results. I find that the SPT measurements are consistent with Horizon-AGN, falling within 0.4σ at low-z and 0.5σ at high-z, while the ACT measurements are very different from Horizon-AGN, off by 6.9σ at low-z and 14.6σ at high-z. Additionally, the SPT measurements are loosely inconsistent with Horizon-NoAGN, off by 1.8σ at low-z but within 0.6σ at high-z, while the ACT measurements are loosely consistent with Horizon-NoAGN (at least much more so than with Horizon-AGN), falling within 0.8σ at low-z but off by 1.9σ at high-z.
In this work, I present stacked CMB measurements of a large number of elliptical galaxies never before measured using this method. I split the galaxies into two redshift groups, "low-z" for z=0.5-1.0 and “high-z” for z=1.0-1.5. I make two independent sets of CMB measurements using data from the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT), respectively, and I use data from the Planck telescope to account for contamination from dust emission. With SPT I find average thermal energies of 7.6(+3.0/−2.3) × 10^60 erg for 937 low-z galaxies, and 6.0(+7.7/−6.3) × 10^60 erg for 240 high-z galaxies. With ACT I find average thermal energies of 5.6(+5.9/−5.6) × 10^60 erg for 227 low-z galaxies, and 7.0(+4.7/−4.4) × 10^60 erg for 529 high-z galaxies.
I then attempt to further interpret the physical meaning of my observational results by incorporating two large-scale cosmological hydrodynamical simulations, one with (Horizon-AGN) and one without (Horizon-NoAGN) AGN feedback. I extract simulated tSZ measurements around a population of galaxies equivalent to those used in my observational work, with matching mass distributions, and compare the results. I find that the SPT measurements are consistent with Horizon-AGN, falling within 0.4σ at low-z and 0.5σ at high-z, while the ACT measurements are very different from Horizon-AGN, off by 6.9σ at low-z and 14.6σ at high-z. Additionally, the SPT measurements are loosely inconsistent with Horizon-NoAGN, off by 1.8σ at low-z but within 0.6σ at high-z, while the ACT measurements are loosely consistent with Horizon-NoAGN (at least much more so than with Horizon-AGN), falling within 0.8σ at low-z but off by 1.9σ at high-z.
ContributorsSpacek, Alexander Edward (Author) / Scannapieco, Evan (Thesis advisor) / Bowman, Judd (Committee member) / Butler, Nat (Committee member) / Groppi, Chris (Committee member) / Young, Patrick (Committee member) / Arizona State University (Publisher)
Created2017
Description
High-energy explosive phenomena, Gamma-Ray Bursts (GRBs) and Supernovae (SNe), provide unique laboratories to study extreme physics and potentially open up the new discovery window of Gravitational-wave astronomy.
Uncovering the intrinsic variability of GRBs constrains the size of the GRB emission region, and ejecta velocity, in turn provides hints on the nature of GRBs and their progenitors. We develop a novel method which ties together wavelet and structure-function analyses to measure, for the first time, the actual minimum variability timescale, Delta t_min, of GRB light curves. Implementing our technique to the largest sample of GRBs collected by Swift and Fermi instruments reveals that only less than 10% of GRBs exhibit evidence for variability on timescales below 2 ms. Investigation on various energy bands of the Gamma-ray Burst Monitor (GBM) onboard Fermi shows that the tightest constraints on progenitor radii derive from timescales obtained from the hardest energy channel of light curves (299--1000 keV). Our derivations for the minimum Lorentz factor, Gamma_min, and the minimum emission radius, R = 2c Gamma_min^2 Delta t_min / (1+z), find Gamma < 400 which imply typical emission radii R ~ 1 X 10^14 cm for long-duration GRBs and R ~ 3 X 10^13 cm for short-duration GRBs (sGRBs).
I present the Reionization and Transients InfraRed (RATIR) followup of LIGO/Virgo Gravitational-wave events especially for the G194575 trigger. I show that expanding our pipeline to search for either optical riZ or near-infrared YJH detections (3 or more bands)
should result in a false-alarm-rate ~1% (one candidate in the vast 100 deg^2 LIGO error region) and an efficiency ~90%.
I also present the results of a 5-year comprehensive SN search by the Palomar Transient Factory aimed to measure the SN rates in the local Luminous Infrared Galaxies. We find that the SN rate of the sample, 0.05 +/- 0.02 1/yr (per galaxy), is consistent with that expected from the theoretical prediction, 0.060 +/- 0.002 1/yr (per galaxy).
Uncovering the intrinsic variability of GRBs constrains the size of the GRB emission region, and ejecta velocity, in turn provides hints on the nature of GRBs and their progenitors. We develop a novel method which ties together wavelet and structure-function analyses to measure, for the first time, the actual minimum variability timescale, Delta t_min, of GRB light curves. Implementing our technique to the largest sample of GRBs collected by Swift and Fermi instruments reveals that only less than 10% of GRBs exhibit evidence for variability on timescales below 2 ms. Investigation on various energy bands of the Gamma-ray Burst Monitor (GBM) onboard Fermi shows that the tightest constraints on progenitor radii derive from timescales obtained from the hardest energy channel of light curves (299--1000 keV). Our derivations for the minimum Lorentz factor, Gamma_min, and the minimum emission radius, R = 2c Gamma_min^2 Delta t_min / (1+z), find Gamma < 400 which imply typical emission radii R ~ 1 X 10^14 cm for long-duration GRBs and R ~ 3 X 10^13 cm for short-duration GRBs (sGRBs).
I present the Reionization and Transients InfraRed (RATIR) followup of LIGO/Virgo Gravitational-wave events especially for the G194575 trigger. I show that expanding our pipeline to search for either optical riZ or near-infrared YJH detections (3 or more bands)
should result in a false-alarm-rate ~1% (one candidate in the vast 100 deg^2 LIGO error region) and an efficiency ~90%.
I also present the results of a 5-year comprehensive SN search by the Palomar Transient Factory aimed to measure the SN rates in the local Luminous Infrared Galaxies. We find that the SN rate of the sample, 0.05 +/- 0.02 1/yr (per galaxy), is consistent with that expected from the theoretical prediction, 0.060 +/- 0.002 1/yr (per galaxy).
ContributorsGolkhou, Vahid Zachary (Author) / Butler, Nathaniel R. (Thesis advisor) / Bowman, Judd (Committee member) / Jansen, Rolf A (Committee member) / Patience, Jennifer (Committee member) / Scannapieco, Evan (Committee member) / Arizona State University (Publisher)
Created2017
Description
The balance between relative numbers, lifetime, and habitable zone (HZ) size of K stars (0.6 – 0.9 M⊙) in comparison with M (0.08 – 0.6 M⊙) and G (0.9 – 1.1 M⊙) stars makes them candidates to host “super-habitable” planets. Understanding the high- energy radiation environment of planets around these stars is crucial, since ultraviolet (UV) and X-ray radiation may cause severe photodissociation and ionization of the atmosphere, with the potential for complete erosion. In this thesis, I present the first broad study of the UV and X-ray evolution of K stars. I first focused on Galaxy Evolution Explorer (GALEX) and Ro ̈ntgen Satellit (ROSAT) photometric UV and X-ray evolutions of K stars and compared this with the age evolution of both early- (0.35 – 0.6 M⊙) and late-M (0.08 – 0.35 M⊙) stars. I found that the fractional UV and X-ray flux from M and K stars is similar; however, the wider and farther HZs of K stars mean that there is less incident UV radiation on HZ planets. Next, I led a spectroscopic study of 41 K stars using Hubble Space Telescope Cosmic Origins Spectrograph (HST/COS) data to show that the UV line and continua emission show no decrease in flux beyond 650 Myr whereas early-M star flux declines by 150 Myr; therefore, the K star intrinsic UV flux is greater than early-M stars after this time. I suggest that this phenomenon is related to K star rotational spin-down stalling. Lastly, I revisited the GALEX and ROSAT data with newly-available distances from the Gaia mission for both K and M stars. I find that the UV flux for K stars is an order of magnitude higher for M stars at all ages and the flux in their respective HZs is similar. However, K star X-ray flux is an order of magnitude less in the HZ than for M stars. The age of decline shows a dependency on wavelength, a phenomenon which is not seen in either the early- or late-M star data. These results suggest thatK stars may not exhibit quite the advantage as HZ planet host stars as the scientific community originally thought.
ContributorsRichey-Yowell, Tyler (Author) / Shkolnik, Evgenya (Thesis advisor) / Patience, Jennifer (Committee member) / Jacobs, Daniel (Committee member) / Bowman, Judd (Committee member) / Young, Patrick (Committee member) / Arizona State University (Publisher)
Created2022
Description
Nebular emission-lines offer a powerful tool for studying the physical properties and chemical compositions of galaxies in the near and distant universe. They are excellent tracers of star formation activity in galaxies as well as efficient probes of intergalactic medium in the early universe. This dissertation presents findings from three different studies of emission-line galaxies (a.k.a. line emitters) at low and high redshifts, based on imaging and spectroscopic observations. The first study explores Hα emitters at z ~ 0.6 from the Cosmic Deep And Wide Narrow-band (DAWN) survey, providing robust measurements of the Hα luminosity function (LF) and the star-formation rate density (SFRD) at z ~ 0.6. The effects of different dust-extinction corrections on the measured LF were also investigated in this study. Owing to the observing strategy employed in this survey, this study demonstrates the importance of performing deep and wide-field observations, in order to robustly constrain the entire LF. In the second study, 21 Lyman-α emitter (LAE) candidates at z ~ 7 from the Lyman-Alpha Galaxies in the Epoch of Reionization (LAGER) survey were followed up spectroscopically, using Low Resolution Imaging Spectrometer (LRIS) on the Keck telescope. 15 of these were confirmed to be LAEs, obtaining a spectroscopic confirmation success rate of ~ 80% for LAGER LAE candidates. Apart from Lyman- α, no other rest-frame ultra-violet (UV) nebular lines were detected, with a 2σ upper limit for the ratio of NV/Lyα ≲ 0.27. These confirmations help validate the neutral Hydrogen fraction estimates from LAGER, which is consistent with a fully ionized universe at z ~ 7. The final study investigated the presence of black hole/active galactic nuclei (AGN) signatures among Green Pea (GP) galaxies, using mid-infrared (MIR) observations from the Wide-field Infrared Survey Explorer (WISE) mission. 31 GPs were selected as candidate AGN based on a stringent MIR color-color diagnostic including two GPs exhibiting notable variability in the shorter two WISE bandpasses. Given that GPs are one of the best analogs of high-redshift galaxies, findings from this study suggest that AGN activity could be responsible for the hard ionizing radiation observed in some GPs, which has crucial implications on the sources likely to have contributed towards cosmic reionization.
ContributorsHarish, Santosh Mudigundam (Author) / Rhoads, James E. (Thesis advisor) / Jacobs, Daniel C. (Thesis advisor) / Malhotra, Sangeeta (Committee member) / Bowman, Judd (Committee member) / Jansen, Rolf (Committee member) / Arizona State University (Publisher)
Created2022
Description
This dissertation details the development of an open source, frequency domain multiplexed (FDM) readout for large-format arrays of superconducting lumped-element kinetic inductance detectors (LEKIDs). The system architecture is designed to meet the requirements of current and next generation balloon-borne and ground-based submillimeter (sub-mm), far-infrared (FIR) and millimeter-wave (mm-wave) astronomical cameras, whose science goals will soon drive the pixel counts of sub-mm detector arrays from the kilopixel to the megapixel regime. The in-flight performance of the readout system was verified during the summer, 2018 flight of ASI's OLIMPO balloon-borne telescope, from Svalbard, Norway. This was the first flight for both LEKID detectors and their associated readout electronics. In winter 2019/2020, the system will fly on NASA's long-duration Balloon Borne Large Aperture Submillimeter Telescope (BLAST-TNG), a sub-mm polarimeter which will map the polarized thermal emission from cosmic dust at 250, 350 and 500 microns (spatial resolution of 30", 41" and 59"). It is also a core system in several upcoming ground based mm-wave instruments which will soon observe at the 50 m Large Millimeter Telescope (e.g., TolTEC, SuperSpec, MUSCAT), at Sierra Negra, Mexico.
The design and verification of the FPGA firmware, software and electronics which make up the system are described in detail. Primary system requirements are derived from the science objectives of BLAST-TNG, and discussed in the context of relevant size, weight, power and cost (SWaP-C) considerations for balloon platforms. The system was used to characterize the instrumental performance of the BLAST-TNG receiver and detector arrays in the lead-up to the 2019/2020 flight attempt from McMurdo Station, Antarctica. The results of this characterization are interpreted by applying a parametric software model of a LEKID detector to the measured data in order to estimate important system parameters, including the optical efficiency, optical passbands and sensitivity.
The role that magnetic fields (B-fields) play in shaping structures on various scales in the interstellar medium is one of the central areas of research which is carried out by sub-mm/FIR observatories. The Davis-Chandrasekhar-Fermi Method (DCFM) is applied to a BLASTPol 2012 map (smoothed to 5') of the inner ~1.25 deg2 of the Carina Nebula Complex (CNC, NGC 3372) in order to estimate the strength of the B-field in the plane-of-the-sky (B-pos). The resulting map contains estimates of B-pos along several thousand sightlines through the CNC. This data analysis pipeline will be used to process maps of the CNC and other science targets which will be produced during the upcoming BLAST-TNG flight. A target selection survey of five nearby external galaxies which will be mapped during the flight is also presented.
The design and verification of the FPGA firmware, software and electronics which make up the system are described in detail. Primary system requirements are derived from the science objectives of BLAST-TNG, and discussed in the context of relevant size, weight, power and cost (SWaP-C) considerations for balloon platforms. The system was used to characterize the instrumental performance of the BLAST-TNG receiver and detector arrays in the lead-up to the 2019/2020 flight attempt from McMurdo Station, Antarctica. The results of this characterization are interpreted by applying a parametric software model of a LEKID detector to the measured data in order to estimate important system parameters, including the optical efficiency, optical passbands and sensitivity.
The role that magnetic fields (B-fields) play in shaping structures on various scales in the interstellar medium is one of the central areas of research which is carried out by sub-mm/FIR observatories. The Davis-Chandrasekhar-Fermi Method (DCFM) is applied to a BLASTPol 2012 map (smoothed to 5') of the inner ~1.25 deg2 of the Carina Nebula Complex (CNC, NGC 3372) in order to estimate the strength of the B-field in the plane-of-the-sky (B-pos). The resulting map contains estimates of B-pos along several thousand sightlines through the CNC. This data analysis pipeline will be used to process maps of the CNC and other science targets which will be produced during the upcoming BLAST-TNG flight. A target selection survey of five nearby external galaxies which will be mapped during the flight is also presented.
ContributorsGordon, Samuel, Ph.D (Author) / Mauskopf, Philip (Thesis advisor) / Groppi, Christopher (Committee member) / Scowen, Paul (Committee member) / Bowman, Judd (Committee member) / Jacobs, Daniel (Committee member) / Arizona State University (Publisher)
Created2019
Description
Reionization is the phase transition of intergalactic atoms from being neutral to
becoming fully ionized. This process began ∼400 Myr after the Big Bang, when the first
stars and black holes began emitting ionizing radiation from stellar photospheres and
accretion disks. Reionization completed when all of the neutral matter between galaxies
became ionized ∼1 Gyr after the Big Bang, and the Universe became transparent as
it is today.
Characteristics of the galaxies that drove reionization are mostly unknown. The
physical mechanisms that create ionizing radiation inside these galaxies, and the
paths for this light to escape are even more unclear. To date, only a small fraction of
the numerous searches for this escaping light have been able to detect a faint signal
from distant galaxies, and no consensus on how Reionization was completed has been
established.
In this dissertation, I discuss the evolution of the atomic matter between galaxies
from its initially ionized state, to its current re-ionized state, potential sources of
re-ionizing energy, and the theoretical and observational status of the characteristics of
these sources. I also present new constraints on what fraction of the ionizing radiation
escapes from galaxies using Hubble Space Telescope UV imaging, theoretical models
of the stellar and accretion disk radiation, and models of the absorption of ionizing
radiation by the intergalactic medium.
becoming fully ionized. This process began ∼400 Myr after the Big Bang, when the first
stars and black holes began emitting ionizing radiation from stellar photospheres and
accretion disks. Reionization completed when all of the neutral matter between galaxies
became ionized ∼1 Gyr after the Big Bang, and the Universe became transparent as
it is today.
Characteristics of the galaxies that drove reionization are mostly unknown. The
physical mechanisms that create ionizing radiation inside these galaxies, and the
paths for this light to escape are even more unclear. To date, only a small fraction of
the numerous searches for this escaping light have been able to detect a faint signal
from distant galaxies, and no consensus on how Reionization was completed has been
established.
In this dissertation, I discuss the evolution of the atomic matter between galaxies
from its initially ionized state, to its current re-ionized state, potential sources of
re-ionizing energy, and the theoretical and observational status of the characteristics of
these sources. I also present new constraints on what fraction of the ionizing radiation
escapes from galaxies using Hubble Space Telescope UV imaging, theoretical models
of the stellar and accretion disk radiation, and models of the absorption of ionizing
radiation by the intergalactic medium.
ContributorsSmith, Brent Matthew (Author) / Windhorst, Rogier A. (Thesis advisor) / Bowman, Judd (Committee member) / Borthakur, Sanchayeeta (Committee member) / Butler, Nathaniel (Committee member) / Mauskopf, Phillip (Committee member) / Arizona State University (Publisher)
Created2019