Cosmic Illumination: Revealing the Hidden Gaseous Ecosystem Around Galaxies

The flow of gas between galaxies and their surroundings is a fundamental driver of galaxy evolution, both fueling and quenching the formation of stars. Until recently, tracking this nearly invisible gas was done with a single pinpoint quasar line of sight through a galaxy. We are now stepping into a new era of observations that allow for directly tracking and mapping this gas in emission around individual galaxies in detail, with a thousand-fold increase in lines of sight per galaxy. I will present ultra-deep emission maps with the Keck Cosmic Web Imager of the gas flows around a nearby starbursting galaxy. Observations such as these are a key discovery area for galaxy evolution science in the next decade.