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- All Subjects: Astronomy
- Creators: Bowman, Judd
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
The Cosmic Microwave Background (CMB) has provided precise information on the evolution of the Universe and the current cosmological paradigm. The CMB has not yet provided definitive information on the origin and strength of any primordial magnetic fields or how they affect the presence of magnetic fields observed throughout the cosmos. This work outlines an alternative method to investigating and identifying the presence of cosmic magnetic fields. This method searches for Faraday Rotation (FR) and specifically uses polarized CMB photons as back-light. I find that current generation CMB experiments may be not sensitive enough to detect FR but next generation experiments should be able to make highly significant detections. Identifying FR with the CMB will provide information on the component of magnetic fields along the line of sight of observation.
The 21cm emission from the hyperfine splitting of neutral Hydrogen in the early universe is predicted to provide precise information about the formation and evolution of cosmic structure, complementing the wealth of knowledge gained from the CMB.
21cm cosmology is a relatively new field, and precise measurements of the Epoch of Reionization (EoR) have not yet been achieved. In this work I present 2σ upper limits on the power spectrum of 21cm fluctuations (Δ²(k)) probed at the cosmological wave number k from the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) 64 element deployment. I find upper limits on Δ²(k) in the range 0.3 < k < 0.6 h/Mpc to be (650 mK)², (450 mK)², (390 mK)², (250 mK)², (280mK)², (250 mK)² at redshifts z = 10.87, 9.93, 8.91, 8.37, 8.13 and 7.48 respectively
Building on the power spectrum analysis, I identify a major limiting factor in detecting the 21cm power spectrum.
This work is concluded by outlining a metric to evaluate the predisposition of redshifted 21cm interferometers to foreground contamination in power spectrum estimation. This will help inform the construction of future arrays and enable high fidelity imaging and
cross-correlation analysis with other high redshift cosmic probes like the CMB and other upcoming all sky surveys. I find future
arrays with uniform (u,v) coverage and small spectral evolution of their response in the (u,v,f) cube can minimize foreground leakage while pursuing 21cm imaging.
The 21cm emission from the hyperfine splitting of neutral Hydrogen in the early universe is predicted to provide precise information about the formation and evolution of cosmic structure, complementing the wealth of knowledge gained from the CMB.
21cm cosmology is a relatively new field, and precise measurements of the Epoch of Reionization (EoR) have not yet been achieved. In this work I present 2σ upper limits on the power spectrum of 21cm fluctuations (Δ²(k)) probed at the cosmological wave number k from the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) 64 element deployment. I find upper limits on Δ²(k) in the range 0.3 < k < 0.6 h/Mpc to be (650 mK)², (450 mK)², (390 mK)², (250 mK)², (280mK)², (250 mK)² at redshifts z = 10.87, 9.93, 8.91, 8.37, 8.13 and 7.48 respectively
Building on the power spectrum analysis, I identify a major limiting factor in detecting the 21cm power spectrum.
This work is concluded by outlining a metric to evaluate the predisposition of redshifted 21cm interferometers to foreground contamination in power spectrum estimation. This will help inform the construction of future arrays and enable high fidelity imaging and
cross-correlation analysis with other high redshift cosmic probes like the CMB and other upcoming all sky surveys. I find future
arrays with uniform (u,v) coverage and small spectral evolution of their response in the (u,v,f) cube can minimize foreground leakage while pursuing 21cm imaging.
ContributorsKolopanis, Matthew John (Author) / Bowman, Judd (Thesis advisor) / Mauskopf, Philip (Thesis advisor) / Lunardini, Cecilia (Committee member) / Chamberlin, Ralph (Committee member) / Vachaspati, Tanmay (Committee member) / Arizona State University (Publisher)
Created2018
Description
Using data from the Arizona Radio Observatory Submillimeter Telescope, we have studied the active, star-forming region of the R Coronae Australis molecular cloud in 12CO (2-1), 13CO (2-1), and HCO+ (3-2). We baselined and mapped the data using CLASS. It was then used to create integrated intensity, outflow, and centroid velocity maps in IDL. These clearly showed the main large outflow, and then we identified a few other possible outflows.
ContributorsBlumm, Margaret Elizabeth (Author) / Groppi, Christopher (Thesis director) / Bowman, Judd (Committee member) / Mauskopf, Philip (Committee member) / Barrett, The Honors College (Contributor) / School of Earth and Space Exploration (Contributor)
Created2014-05
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
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 Star Planet Activity Research CubeSat (SPARCS) will be a 6U CubeSat devoted to photometric monitoring of M dwarfs in the far-ultraviolet (FUV) and near-ultraviolet (NUV) (160 and 280 nm respectively), measuring the time-dependent spectral slope, intensity and evolution of M dwarf stellar UV radiation. The delta-doped detectors baselined for SPARCS have demonstrated more than five times the in-band quantum efficiency of the detectors of GALEX. Given that red:UV photon emission from cool, low-mass stars can be million:one, UV observation of thes stars are susceptible to red light contamination. In addition to the high efficiency delta-doped detectors, SPARCS will include red-rejection filters to help minimize red leak. Even so, careful red-rejection and photometric calibration is needed. As was done for GALEX, white dwarfs are used for photometric calibration in the UV. We find that the use of white dwarfs to calibrate the observations of red stars leads to significant errors in the reported flux, due to the differences in white dwarf and red dwarf spectra. Here we discuss the planned SPARCS calibration model and the color correction, and demonstrate the importance of this correction when recording UV measurements of M stars taken by SPARCS.
ContributorsOsby, Ella (Author) / Shkolnik, Evgenya (Thesis director) / Ardila, David (Committee member) / School of Earth and Space Exploration (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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
In the upcoming decade, powerful new astronomical facilities such as the James Webb Space Telescope (JWST), the Square Kilometer Array (SKA), and ground-based 30-meter telescopes will open up the epoch of reionization to direct astronomical observation. One of the primary tools used to understand the bulk astrophysical properties of the high-redshift universe are empirically-derived star-forming laws, which relate observed luminosity to fundamental astrophysical quantities such as star formation rate. The radio/infrared relation is one of the more mysterious of these relations: despite its somewhat uncertain astrophysical origins, this relation is extremely tight and linear, with 0.3 dex of scatter over five orders of magnitude in galaxy luminosity. The effects of primordial metallicities on canonical star-forming laws is an open question: a growing body of evidence suggests that the current empirical star forming laws may not be valid in the unenriched, metal-poor environment of the very early universe.
In the modern universe, nearby dwarf galaxies with less than 1/10th the Solar metal abundance provide an opportunity to recalibrate our star formation laws and study the astrophysics of extremely metal-deficient (XMD) environments in detail. I assemble a sample of nearby dwarf galaxies, all within 100 megaparsecs, with nebular oxygen abundances between 1/5th and 1/50th Solar. I identify the subsample of these galaxies with space-based mid- and far-infrared data, and investigate the effects of extreme metallicities on the infrared-radio relationship. For ten of these galaxies, I have acquired 40 hours of observations with the Jansky Very Large Array (JVLA). C-band (4-8 GHz) radio continuum emission is detected from all 10 of these galaxies. These represent the first radio continuum detections from seven galaxies in this sample: Leo A, UGC 4704, HS 0822+3542, SBS 0940+544, and SBS 1129+476. The radio continuum in these galaxies is strongly associated with the presence of optical H-alpha emission, with spectral slopes suggesting a mix of thermal and non-thermal sources. I use the ratio of the radio and far-infrared emission to investigate behavior of the C-band (4-8 GHz) radio/infrared relation at metallicities below 1/10th Solar.
I compare the low metallicity sample with the 4.8 GHz radio/infrared relationship from the KINGFISHER nearby galaxy sample Tabatabaei et al. 2017 and to the 1.4 GHz radio/infrared relationship from the blue compact dwarf galaxy sample of Wu et al. 2008. The infrared/radio ratio q of the low metallicity galaxies is below the average q of star forming galaxies in the modern universe. I compare these galaxies' infrared and radio luminosities to their corresponding Halpha luminosities, and find that both the infrared/Halpha and the radio/H-alpha ratios are reduced by nearly 1 dex in the low metallicity sample vs. higher metallicity galaxies; however the deficit is not straightforwardly interpreted as a metallicity effect.
In the modern universe, nearby dwarf galaxies with less than 1/10th the Solar metal abundance provide an opportunity to recalibrate our star formation laws and study the astrophysics of extremely metal-deficient (XMD) environments in detail. I assemble a sample of nearby dwarf galaxies, all within 100 megaparsecs, with nebular oxygen abundances between 1/5th and 1/50th Solar. I identify the subsample of these galaxies with space-based mid- and far-infrared data, and investigate the effects of extreme metallicities on the infrared-radio relationship. For ten of these galaxies, I have acquired 40 hours of observations with the Jansky Very Large Array (JVLA). C-band (4-8 GHz) radio continuum emission is detected from all 10 of these galaxies. These represent the first radio continuum detections from seven galaxies in this sample: Leo A, UGC 4704, HS 0822+3542, SBS 0940+544, and SBS 1129+476. The radio continuum in these galaxies is strongly associated with the presence of optical H-alpha emission, with spectral slopes suggesting a mix of thermal and non-thermal sources. I use the ratio of the radio and far-infrared emission to investigate behavior of the C-band (4-8 GHz) radio/infrared relation at metallicities below 1/10th Solar.
I compare the low metallicity sample with the 4.8 GHz radio/infrared relationship from the KINGFISHER nearby galaxy sample Tabatabaei et al. 2017 and to the 1.4 GHz radio/infrared relationship from the blue compact dwarf galaxy sample of Wu et al. 2008. The infrared/radio ratio q of the low metallicity galaxies is below the average q of star forming galaxies in the modern universe. I compare these galaxies' infrared and radio luminosities to their corresponding Halpha luminosities, and find that both the infrared/Halpha and the radio/H-alpha ratios are reduced by nearly 1 dex in the low metallicity sample vs. higher metallicity galaxies; however the deficit is not straightforwardly interpreted as a metallicity effect.
ContributorsMonkiewicz, Jacqueline Ann (Author) / Bowman, Judd (Thesis advisor) / Scowen, Paul (Thesis advisor) / Mauskopf, Philip (Committee member) / Scannapieco, Evan (Committee member) / Jansen, Rolf (Committee member) / Arizona State University (Publisher)
Created2018