Matching Items (88)
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
Kinetic Inductance Detectors (KIDs) offer highly sensitive solutions for millimeter and submillimeter wave astronomy. KIDs are superconducting detectors capable of measuring photon energy and arrival time. KIDs use the change in surface impedance of the superconductor when an incident photon is absorbed and breaks Cooper pairs in the superconducting material. This occurs when KIDs use a superconducting resonator: when a photon is incident on the inductor, the photon is absorbed and inductance increases and the resonant frequency decreases. The resonator is weakly coupled to a transmission line which naturally allows for multiplexing to allow up to thousands of detectors to be read out on one transmission line. In this thesis a KID is presented to be used at submillimeter wavelengths. I optimized a polarization-sensitive aluminum absorber for future Balloon-borne Large Aperture Submillimeter Telescope (BLAST) missions. BLAST is designed to investigate polarized interstellar dust and the role of magnetic fields on star formation. As part of the effort to develop aluminum KIDs for BLAST, I investigated the optical coupling method including different feedhorn structures and a hybrid design. I present a suite of simulations calculating the absorption efficiency of the absorber. The optimized KID is a feedhorn/waveguide coupled front-illuminated detector that achieves 70% absorption over the frequency band centered at 250um.
ContributorsChamberlin, Kathryn (Author) / Mauskopf, Philip (Thesis advisor) / Trichopoulos, Georgios (Committee member) / Zeinolabedinzadeh, Saeed (Committee member) / Arizona State University (Publisher)
Created2022
Description
As a demonstration study of low-resolution spectrophotometry, the photometric redshift estimation with narrow-band optical photometry of nine galaxy clusters is presented in this thesis. A complete data reduction process of the photometryusing up to 16 10nm wide narrow-band optical filters from 490nm − 660nm are provided. Narrow-band photometry data are combined with broad-band photometry (SDSS/Pan-STARRS) for photometric redshift fitting. With available spectroscopic
redshift data from eight of the fields, I evaluated the fitted photometric redshift results and showed that combining broad-band photometric data with narrow-band data result in improvements of factor 2-3, compared to redshift estimations from
broad-band photometry alone. With 15 or 16 narrow-band data combined with SDSS (Sloan Digital Sky Survey) or Pan-STARRS1 (The Panoramic Survey Telescope and Rapid Response System) data, a Normalized Median Absolute Deviation of σNMAD ∼ 0.01−0.016 can be achieved.
The multiband images of galaxy cluster ABELL 611 have been used to further study intracluster light around its brightest cluster galaxy (BCG). It can be shown here that fitting of BCG+ICL stellar properties using the averaged 1-dimensional
radial profile is possible up to ∼ 100kpc within this cluster. The decreasing in age of the stellar population as a function of radius from the BCG+ICL profile, though not entirely conclusive, demonstrates possible future application of low-resolution
spectrophotometry on the ICL studies.
Finally, Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx) mission planning study are covered, and a methodology of visualization tool for target availability is described.
ContributorsWang, Pao-Yu (Author) / Mauskopf, Philip (Thesis advisor) / Butler, Nathaniel (Committee member) / Jansen, Rolf (Committee member) / Vachaspati, Tanmay (Committee member) / Arizona State University (Publisher)
Created2022
Description
The first part of this work focuses on the information that neutrinos from core-collapse supernovae (CCSNe) can provide with in the context of multi-messenger astronomy. A CCSN serves as nature’s very own laboratory. Neutrinos from the various phases of a CCSN can be used to gain insights and understanding in a much broader context. The localization of a star using presupernova neutrinos is studied and it is shown that their topology can give the direction to the star with an error of ~ 60 degrees. A new phenomenological description of the neutrino gravitational wave memory effect is built, highlighting its detectability, and physics potential in the present context. It is shown that this effect will be detectable in the near future, for a galactic supernova, at deci-Hertz GW interferometers. A novel idea of how observations of the neutrino GW memory from CCSNe will enable time-triggered searches of supernova neutrinos at megaton (Mt) scale neutrino detectors is also presented. This combination of a deci-Hz GW and a Mt-neutrino detector will allow the latter to detect ~ 3 - 30 supernova neutrino events/Mt/per decade of operation.The second part of this work focuses on studying quantum fields in time and space- dependent backgrounds. Generically, such quantum fields get excited (a phenomenon known as particle production) and the quantum excitations then backreact on the background. This scenario is important in all areas of physics, specifically in the context of gravitation and cosmology. This work discusses some simplified models pertaining to this. In particular, the dynamics of a classical field rolling down a linear potential while it is bi-quadratically coupled to a quantum field is studied. The formation of global topological defects in d-dimensions as a result of spontaneous symmetry breaking during a quantum phase transition is also studied. Furthermore, a sine-Gordon kink-antikink collision in the presence of interactions with a scalar field is considered and the regimes of breather and long lived oscillon formation are found.
ContributorsMukhopadhyay, Mainak (Author) / Lunardini, Cecilia C (Thesis advisor) / Vachaspati, Tanmay T (Committee member) / Baumgart, Matthew M (Committee member) / Timmes, Francis F.X. (Committee member) / Arizona State University (Publisher)
Created2022
Description
Gamma-ray bursts (GRBs) are a type of astrophysical transient resulting from the most energetic explosions known in the universe. The explosions occur in distant galaxies, and their bright initial emission may only last a few seconds. Colibri is a telescope being built at the San Pedro Martir Observatory in Baja, CA, MX with high sensitivity in order to study these events at a high redshift. Due to how quickly GRBs occur, it is essential to develop an image reduction pipeline that can quickly and accurately detect these events. Using existing image reduction software from Coatli, which was programmed and optimized for speed using python, numerous time trials were performed in order to determine if the pipeline meets the time requirements with various factors being adjusted. The goal of this experiment is for the telescope to respond to, capture, and reduce the images in under 3 minutes. It was determined that the reduction was optimized when the number of files to be reduced was set equal to 16 or higher by changing the batch number and the blank sky subtraction function was performed. As for the number of exposures, one can take up to four 30 second exposures or twenty 5 second exposures and reduce them in under 3 minutes.
ContributorsHeiligenstein, Wren (Author) / Butler, Nathaniel (Thesis director) / Jansen, Rolf (Committee member) / Dimitrova, Tzvetelina (Committee member) / Barrett, The Honors College (Contributor) / School of Earth and Space Exploration (Contributor)
Created2024-05
Description
For this project, the diffuse supernova neutrino background (DSNB) has been calculated based on the recent direct supernova rate measurements and neutrino spectrum from SN1987A. The estimated diffuse electron antineutrino flux is ∼ 0.10 – 0.59 /cm2/s at 99% confidence level, which is 5 times lower than the Super-Kamiokande 2012 upper limit of 3.0 /cm2/s, above energy threshold of 17.3 MeV. With a Megaton scale water detector, 40 events could be detected above the threshold per year. In addition, the detectability of neutrino bursts from direct black hole forming collapses (failed supernovae) at Megaton detectors is calculated. These neutrino bursts are energetic and with short time duration, ∼ 1s. They could be identified by the time coincidence of N ≥2 or N ≥3 events within 1s time window from nearby (4 – 5 Mpc) failed supernovae. The detection rate of these neutrino bursts could get up to one per decade. This is a realistic way to detect a failed supernova and gives a promising method for studying the physics of direct black hole formation mechanism. Finally, the absorption of ultra high energy (UHE) neutrinos by the cosmic neutrino background, with full inclusion of the effect of the thermal distribution of the background on the resonant annihilation channel, is discussed. Results are applied to serval models of UHE neutrino sources. Suppression effects are strong for sources that extend beyond z ∼ 10. This provides a fascinating probe of the physics of the relic neutrino background in the unexplored redshift interval z ∼ 10 – 100. Ultimately this research will examine the detectability of DSNB, neutrino bursts from failed supernovae and absorption effects in the neutrino spectrum.
ContributorsYang, Lili, 1970- (Author) / Lunardini, Cecilia (Thesis advisor) / Alarcon, Ricardo (Committee member) / Shovkovy, Igor (Committee member) / Timmes, Francis (Committee member) / Vachaspati, Tanmay (Committee member) / Arizona State University (Publisher)
Created2013
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
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
The James Webb Space Telescope (JWST) is expected to revolutionize the current understanding of Jovian worlds over the coming decade. However, as the field pushes towards characterizing cooler, smaller, “terrestrial-like” planets, dedicated next-generation facilities will be required to tease out the small spectral signatures indicative of biological activity. Here, the feasibility of determining atmospheric properties, from near to mid-infrared transmission spectra, of transiting temperate terrestrial M-dwarf companions, has been evaluated. Specifically, atmospheric retrievals were utilized to explore the trade space between spectral resolution, wavelength coverage, and signal-to-noise on the ability to both detect molecular species and constrain their abundances. Increasing spectral resolution beyond R=100 for near-infrared wavelengths, shorter than 5um, proves to reduce the degeneracy between spectral features of different molecules and thus greatly benefits the abundance constraints. However, this benefit is greatly diminished beyond 5um as any overlap between broad features in the mid-infrared does not deconvolve with higher resolutions. Additionally, the inclusion of features beyond 11um did not meaningfully improve the detection significance nor abundance constraints results. The findings of this study indicate that an instrument with continuous wavelength coverage from approximately 2-11um and with a resolution of R~50-300, would be capable of detecting H2O, CO2, CH4, O3, and N2O in the atmosphere of an Earth-analog transiting an M-dwarf (magK=8.0) within 50 transits, and obtain better than an order-of-magnitude constraint on each of their abundances.
The Origins Space Telescope (Origins) is one of four flagship mission concepts, under review by the 2020 Decadal Survey, that may take the mantle of the next-generation space-based observatory. In conjunction with this research, a secondary trade space study was performed on behalf of the Origins Exoplanets Working Group. The primary purpose of this collaboration was to provide a scientific basis to the technical specifications for the mid-infrared detectors onboard the Mid-Infrared Spectrometer Camera Transit Spectrometer (MISC-T) instrument. The results of this work directly contributed to the alteration of the official technical specifications of the instrument design concept.
The Origins Space Telescope (Origins) is one of four flagship mission concepts, under review by the 2020 Decadal Survey, that may take the mantle of the next-generation space-based observatory. In conjunction with this research, a secondary trade space study was performed on behalf of the Origins Exoplanets Working Group. The primary purpose of this collaboration was to provide a scientific basis to the technical specifications for the mid-infrared detectors onboard the Mid-Infrared Spectrometer Camera Transit Spectrometer (MISC-T) instrument. The results of this work directly contributed to the alteration of the official technical specifications of the instrument design concept.
ContributorsTremblay, Luke (Author) / Line, Michael R (Thesis advisor) / Schkolnik, Evgenya (Committee member) / Walker, Sarah (Committee member) / Arizona State University (Publisher)
Created2019
Description
One strategic objective of the National Aeronautics and Space Administration (NASA) is to find life on distant worlds. Current and future missions either space telescopes or Earth-based observatories are frequently used to collect information through the detection of photons from exoplanet atmospheres. The primary challenge is to fully understand the nature of these exo-atmospheres. To this end, atmospheric modeling and sophisticated data analysis techniques are playing a key role in understanding the emission and transmission spectra of exoplanet atmospheres. Of critical importance to the interpretation of such data are the opacities (or absorption cross-sections) of key molecules and atoms. During my Doctor of Philosophy years, the central focus of my projects was assessing and leveraging these opacity data. I executed this task with three separate projects: 1) laboratory spectroscopic measurement of the infrared spectra of CH4 in H2 perturbing gas in order to extract pressure-broadening and pressure-shifts that are required to accurately model the chemical composition of exoplanet atmospheres; 2) computing the H2O opacity data using ab initio line list for pressure and temperature ranges of 10^-6–300 bar and 400–1500 K, and then utilizing these H2O data in radiative transfer models to generate transmission and emission exoplanetary spectra; and 3) assessing the impact of line positions in different H2O opacities on the interpretation of ground-based observational exoplanetary data through the cross-correlation technique.
ContributorsGharib-Nezhad, Ehsan (Author) / Line, Michael R. (Thesis advisor) / Lyons, James R. (Thesis advisor) / Sayres, Scott G. (Committee member) / Heyden, Bjorn Matthias (Committee member) / Arizona State University (Publisher)
Created2019