Rutgers University Astrophysics Seminar

The chemical evolution of galaxies traces a host of physical processes: the accretion of intergalactic gas, feedback-driven outflows, and nucleosynthesis via stars and supernovae. A major goal of current galaxy surveys is to characterize these processes from the epoch of reionization to today, with a particular focus on "Cosmic Noon" — the period at z ~ 2-3 when many of these processes peaked. However, measurements of galaxy "metallicities" in the early Universe remain challenging to acquire and complex to interpret. To this end, I will present recent and on-going results from CECILIA, a Cycle 1 JWST/NIRSpec program targeting 33 galaxies at Cosmic Noon with 30 hours of nebular spectroscopy. CECILIA and other concurrent JWST surveys are transforming our understanding of "metallicity" in the early Universe. I will describe new insights into the evolution of multi-elemental abundances, their connections to stellar populations and formation histories, and emerging best practices for inferring these properties. I will also give particular focus to our recent measurements of a faint "dwarf galaxy" subset of the CECILIA sample, probing galaxies with 10^7-10^9 stars and abundances less than 5% of the Sun. These faintest galaxies provide crucial connections to low mass galaxies from reionization to today, as well as to the processes that shaped the chemistry of our own Milky Way.