Physics & Astronomy ETDs

Publication Date

Fall 8-22-2022

Abstract

Gaining insight into the structure and dynamics of the Milky Way is important for understanding the universe on a large scale. Evolved stars on the Asymptotic Giant Branch are useful for studying the Milky Way because their emission is peaked in the infrared, where interstellar extinction effects are not as dominant. To further understand the physical properties of these objects like luminosity and investigate the Galaxy's structure, we need distance estimates. Obtaining distance estimates for these evolved stars via trigonometric parallax measurements is time-consuming, so infrared surveys studying Asymptotic Giant Branch stars can benefit from other distance estimate methods. In this work, we develop a method of estimating distances to evolved stars using infrared emission and compare results to existing distances. This method uses multiple existing single-epoch survey data to obtain distances, thereby sidestepping the need for new long observing campaigns. Comparisons to VLBI distances using this method show promising results (8 of 14 sources fall within 1$\sigma$ uncertainty) that this method is viable. Comparisons to \emph{Gaia} distance estimates suggest that optical astrometry is not accurate for evolved stars on the Asymptotic Giant Branch. Further development of this method should result in distance estimates to thousand of evolved stars in the Galaxy.

The other main topic in this work is to establish confidence in the Sandia-owned high-consequence plasma code, EMPIRE, to perform validation of experimental data from pulsed-power generators rigorously and provide insight for experiment design. In this work, we present verification problems that can be used in other codes to increase confidence in simulations of relativistic beam transport. Specifically, we use the general plasma code EMPIRE to model and compare with the analytical solution to the evolution of the outer radial envelope of a relativistic charged particle beam. We also outline a benchmark test of a relativistic beam propagating through a vacuum and pressurized gas cell, and present the results between EMPIRE and the hybrid code GAZEL. Furthermore, we perform simulations of the pulsed-power experiment, RKA, using various physics models to understand where our model is lacking as a path to rigorous validation.

Degree Name

Physics

Level of Degree

Doctoral

Department Name

Physics & Astronomy

First Committee Member (Chair)

Dr. Ylva Pihlstrom

Second Committee Member

Dr. Lorant Sjouwerman

Third Committee Member

Dr. Gregory Taylor

Fourth Committee Member

Dr. Keith Cartwright

Language

English

Keywords

AGB, distance estimates, relativistic beam transport

Document Type

Dissertation

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