Using Metals and Stars to Constrain Galaxies’ Past Gaseous Inflows and Outflows
Grace Telford

Abstract:

As galaxies evolve, they must enrich and exchange gas with the surrounding medium, but the timing of these processes and how much gas is involved remain poorly constrained. In this talk, I present my work using observations of the metal and stellar content of galaxies to constrain the history of gas inflow and outflow processes in the local universe. First, I discuss the relationship between stellar mass (M*), gas-phase metallicity (Z), and star formation rate across the local galaxy population, which is thought to encode the strength and duration of metal dilution events due to inflows of metal-poor gas and/or metal-enriched outflows. I show that possible biases in the inferred M* and Z can alter the apparent strength of the correlation, and therefore its physical interpretation. I then focus on the nearby massive spiral galaxy M31, where high-quality, spatially resolved measurements of star formation history (SFH) and dust content and geometry enable a test of standard M* inference techniques. I demonstrate that both recent star formation and variation in star-dust geometry can bias the M* inferred from state-of-the-art models. Finally, I use the same SFHs to calculate the metal mass lost via gaseous outflows from M31 over its lifetime. I calculate the implied metallicity of the circumgalactic medium and show that metals have been redistributed out of the central disk during the last ~1.5 Gyr.