Metallicity as a Tracer of the Baryon Cycle in Modern Cosmological Simulations 19 views

Approximately a century ago, we obtained definitive evidence of galaxies beyond our Milky Way Hubble (1926). In the intervening century, we have developed a sophisticated understanding of how those galaxies formed in the early universe, grew to their present state, and continue to evolve today. Yet, the detailed physical mechanisms driving galaxy assembly remain uncertain. These present day uncertainties are just the modern iteration in the centuries-long co-evolution of our understanding of objects in the night sky with advancements in technology. The problem we face today concerns how to most effectively quantify and study the baryon cycle, which describes the flow of gas in and around galaxies as they evolve. From an observational perspective, the metal content, or metallicity, of a galaxy offers a unique tracer of this cycle. Metals are formed in the cores of stars and ejected back into galaxies when those stars die. Galactic winds then redistribute metals through the disk of a galaxy, but may also eject them from the galaxy entirely. Measuring the metallicity of the galaxy, either in the gas or the stars, therefore provides a direct probe of the current evolutionary state as well as formation history of galaxies. One of the best ways to test our theories of galactic formation and evolution is through the use of cosmological simulations. These simulations include prescriptions for important physics for galaxies such as gravity, star formation, stellar feedback, and chemical enrichment, providing a unique laboratory for stress testing and validating our understanding of the baryon cycle. Yet these models are not without their flaws. Baked into the foundations of these models are several governing assumptions upon which the ``house of cards'' rests. Careful characterization of these assumptions is therefore required to completely appreciate our results. This thesis acts as a bridge between the recent advancements in observations for measuring the metal content of galaxies across space and time with recent efforts building highly sophisticated simulation models. I explore the metallicity of galaxies from ~8 cosmological simulations to understand what story they tell us about galaxies and how we can leverage this information to inform current and upcoming observational campaigns.

PHD (Doctor of Philosophy)

Astronomy; Galaxies; Numerical Simulations; Cosmological Simulations

English

2026-04-27