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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- All Subjects: Astrophysics
In this work I present an improved model for following the formation of Pop III stars, their effects on early galaxy evolution, and how we might search for them. I make use of a new subgrid model of turbulent mixing to accurately follow the time scales required to mix supernova (SN) ejecta -- enriched with heavy elements -- into the pristine gas. I implement this model within a large-scale cosmological simulation and follow the fraction of gas with metallicity below a critical value marking the boundary between Pop III and metal enriched Population II (Pop II) star formation. I demonstrate that accounting for subgrid mixing results in a Pop III stars formation rate that is 2-3 times higher than standard models with the same physical resolution.
I also implement and track a new "Primordial metals" (PM) scalar that tracks the metals generated by Pop III SNe. These metals are taken up by second generation stars and likely result in a subclass of carbon-enhanced, metal-poor (CEMP) stars. By tracking both regular metals and PM, I can model, in post-processing, the elemental abundances of simulation stars. I find good agreement between observations of CEMP-no Milky Way halo stars and second generation stars within the simulation when assuming the first stars had a typical mass of 60 M☉, providing clues as to the Pop III initial mass function.
mining large datasets for transient phenomena. The evolution of massive stars and
compact objects can be studied over cosmic time by identifying supernovae (SNe) and
gamma-ray bursts (GRBs) in other galaxies and determining their redshifts. Modeling
GRBs and their afterglows to probe the jets of GRBs can shed light on the emission
mechanism, rate, and energetics of these events.
In Chapter 1, I discuss the current state of astronomical transient study, including
sources of interest, instrumentation, and data reduction techniques, with a focus
on work in the infrared. In Chapter 2, I present original work published in the
Proceedings of the Astronomical Society of the Pacific, testing InGaAs infrared
detectors for astronomical use (Strausbaugh, Jackson, and Butler 2018); highlights of
this work include observing the exoplanet transit of HD189773B, and detecting the
nearby supernova SN2016adj with an InGaAs detector mounted on a small telescope
at ASU. In Chapter 3, I discuss my work on GRB jets published in the Astrophysical
Journal Letters, highlighting the interesting case of GRB 160625B (Strausbaugh et al.
2019), where I interpret a late-time bump in the GRB afterglow lightcurve as evidence
for a bright-edged jet. In Chapter 4, I present a look back at previous years of
RATIR (Re-ionization And Transient Infra-Red Camera) data, with an emphasis on
the efficiency of following up GRBs detected by the Fermi Space Telescope, before
some final remarks and brief discussion of future work in Chapter 5.