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Ultra–Faint Dwarf Galaxies: Investigating the Evolution of Our Universe & Those Who Study It

Creative Commons 'BY' version 4.0 license

The beginning of our Universe continues to elude us with many unanswered questions, some involving evolutionary histories of the most ancient galaxies — ultra–faint dwarfs (UFDs). Recent optical observation and cosmological simulation advancements have opened new opportunities to study these evolutionary histories. The predominantly ancient stellar populations observed in UFDs suggest their star formation was suppressed by reionization. However, most of the well–studied UFDs are within the central half of the Milky Way (MW) dark matter halo, such that they are consistent with an early accreted population and potentially quenched via environmental processes. To study this possibility, we utilize N–body cosmological simulations, the ELVIS suite, to constrain the distribution of infall times for subhalos likely to host UFDs. For the MW’s UFDs, we find that environment is highly unlikely to play a dominant role in quenching their star formation. Further in UFD exploration, we use this population as a tool to constrain a fundamental Galactic property — dark matter halo mass. As the MW and its satellite system become more entrenched in near–field cosmology, the need for an accurate estimate of the halo mass is increasingly critical. Using new 6D phase–space information for the MW satellite population calculated from Gaia’s early third data release of stellar proper motions to compare to subhalo properties drawn from the Phat ELVIS simulations, we constrain the MW dark matter halo mass to be ~1–1.2 x 10^12 M_sun. This preferred dark matter halo mass for the MW is largely insensitive to the exclusion of systems associated with the Large Magellanic Cloud (LMC), changes in galaxy formation thresholds, and variations in observational completeness. Turning focus inward, current work in progress analyzes, for the first time, chemical abundances in the UFD LMC satellite, Hydrus I. Through abundance trends, we will begin to explore how large scale environments, such as the LMC's dark matter halo, have impacted UFD evolutionary histories. These mostly yet–to–be–explored evolutionary histories of UFD satellites help to refine which are pristine relics of the first galaxies and can serve as the most optimal cosmic sites to search for signatures of the first stars ever formed.

Alongside astrophysics research I have established and led Peer Mentorship programming within my graduate department and a state–wide bridge scholarship program, Cal–Bridge. These peer mentorship activities provide students space to create community around equity through normalizing common struggles, individual holistic success, and determining how to improve their academic experience. While peer mentorship programs are often unsupported within STEM, there is a growing body of research showing how impact–full these programs are. Within my programs, evaluation results show peer mentorship increased growth mindset and recognition of mentor network importance, and has clarified career paths. This type of programming creates leadership opportunities and assists participants in defining and raising confidence in their academic identities. Peer Mentorship empowers participants to have career autonomy while creating supportive, inclusive and equitable communities.

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