Astronomy - Colloquia

Traditionally, galaxy formation theory has been based on connecting observable baryons to dark matter halos and their merger history. But in the past decade, hydrodynamic simulations of galaxy formation have elucidated a somewhat different view, in which galaxy growth is governed by an evolving balance between continual inflow from the intergalactic medium and strong, ubiquitous outflows. In this talk I will discuss the formalism of baryon cycling and the simulations that led to it, and highlight some of the new insights and interpretations that it yields for the stellar, gas, and metal content of galaxies. Of central importance in baryon cycling is the role of circum-galactic gas in regulating galaxy growth, and I will present results from simulations detailing this connection and its observational implications. I will argue that in the coming years, the holistic study of galaxies and their surrounding gas will be the key to understanding galaxy evolution across cosmic time.