Dwarf Galaxies in the Local Universe as Probes of Stellar and Galactic Evolution

Citation

de los Reyes, Mithi Alexa Caballes (2022) Dwarf Galaxies in the Local Universe as Probes of Stellar and Galactic Evolution. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/4bz3-2t66. https://resolver.caltech.edu/CaltechTHESIS:05162022-191523325

Abstract

Low-mass "dwarf" galaxies are numerous, diverse, and relatively simple, making them excellent laboratories for understanding both stellar and galactic evolution. Dwarf galaxies (galaxies with stellar masses 10⁷-10⁹ solar masses) in the nearby universe (out to distances of ~10 Mpc from our own Milky Way, or redshifts z ≾ 0.01), are a particularly interesting population due to their proximity, which allows us to study them in detail on both spatially-resolved and global scales. In this thesis, I present a variety of observational studies investigating star formation and chemical enrichment within nearby dwarf galaxies.

I first use the chemical abundances of individual stars within Local Group dwarf spheroidal galaxies (dSphs) to understand how past stars lived and died. I use this "galactic archaeology" approach to test theoretical models of Type Ia supernovae by investigating the nucleosynthetic products of these supernovae. For example, using medium-resolution spectra from DEIMOS, I measure manganese abundances that place observational constraints on the masses of Type Ia progenitors. I also describe a novel method to measure the delay-time distribution of Type Ia SNe in an individual dSph, which probes the number of white dwarfs involved in Type Ia SNe. Finally, I show how galactic archaeology can also be used to trace star formation using a simple chemical evolution model.

For more distant galaxies, in which individual stars cannot be resolved, galaxy properties can be measured on larger scales. Using the integral field spectrograph KCWI, I produce spatially-resolved maps of dwarf galaxies located in extremely under-dense regions called cosmic voids. The dynamical properties of these galaxies provide insight into the formation of dwarf galaxies in the absence of large-scale environmental effects. On even larger spatial scales, I use photometry to measure the global properties of galaxies and understand the physical processes that drive star formation on galaxy-wide scales.

These studies pave the way for future work with ongoing and upcoming surveys that will map out our local universe---and the dwarf galaxies around us---in unprecedented detail.

Thesis Files