Evolution of Neutral Hydrogen in Galaxies Over One-Third the Age of the Universe With CHILES

Measurements of hydrogen are important in our understanding of the Universe. Following reionization at z ∼ 6, most of the hydrogen outside galaxies is in an ionized state. Within galaxies, hydrogen passes through a neutral phase as it cools and collapses into stars. This work centers around how galactic reservoirs of neutral hydrogen (HI) gas evolve over cosmic time. We know that cosmic star formation peaks at z ∼ 2 and sharply declines to the present, yet we know very little about gas reservoirs in individual galaxies that lead to star formation through these redshifts. The COSMOS HI Large Extragalactic Survey (CHILES) is a 1000-hour program, using the Karl G. Jansky Very Large Array, that images HI in a redshift range of 0 < z < 0.5. In this work, we connect the story of the gas with star formation histories and connect the relation of the gas with the surrounding environment. We present images showing the morphology and kinematics of HI gas in galaxies billions of years back in time.