Abstract
Star-formation depends on the physical conditions of the interstellar medium (ISM), where gas cooling, heating, and feedback from stars and supermassive black holes all compete to drive the evolution of galaxies. My research focuses on characterizing the cold gas from which stars form to better understand the origin of high star-formation rates in luminous, infrared (IR) galaxies today and in the past. I use combined spectroscopy from ALMA, the VLA, and Spitzer to measure physical quantities of interstellar gas and dust at z=0 and z~2. Compact, IR-luminous galaxies at all redshifts exhibit low gas heating efficiencies and high star-formation efficiencies, suggesting a link between the parsec-scale ISM properties of star-forming regions and the global evolution of the galaxy. There is tentative evidence for systematically low gas heating rates at z~2 which may contribute to the high star-formation rates and star-formation efficiencies at early times. I will briefly present ongoing projects and upcoming programs to statistically test this link between the efficiency of star-formation and gas conditions, and discuss how JWST can be used to push diagnostics of the ISM out to higher redshifts