Collaborative Research: Changes in Molecular Gas and Galaxy Properties Over Time in the Era of Integral Field Unit Surveys

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Part 1Changes of a galaxy's properties over time are driven by the quantity of its cold gas, the raw material from which stars form. Thus, understanding the properties of a galaxy's cold gas component will tell us both how the star formation process changes over time and how this affects galaxies. Using a recently completed survey of carbon monoxide gas in a sample of nearby galaxies, the proposers will (1) measure how the molecular gas is used up, in order to test how star formation in the galaxies is affected; (2) map the locations of this gas in the galaxies to determine if/how these locations affect star formation; and (3) measure how the gas is flowing into and out of the galaxies to determine how this affects structural changes in the galaxies over time. In particular, some questions that can be answered from this research include: What factors affect the conversion of molecular gas into stars? How is molecular gas structured? How do galaxies grow and age? This proposal will provide insight into the process of galaxy formation and our understanding of these objects.Part 2This proposal plans to combine spatially resolved spectroscopy of carbon monoxide molecular gas, ionized gas and stellar populations for a sample of 125 nearby galaxies. Measuring spatially-resolved molecular gas depletion time scales as a function of various galaxy properties, using diagnostics of spectral lines to probe diffuse molecular gas, and constraining the rates of gas in- and outflow for these galaxies has the potential to add greatly to our understanding of star formation in normal galaxies.Observations of galaxies across a range of redshifts allow us to witness the growth and aging of the galaxy population. It has long been recognized that these processes are driven by the rise and fall of star formation, which is ultimately linked to the supply of cold gas. Further progress in understanding the regulation of star formation in galaxies, however, requires additional observational constraints beyond the molecular gas mass and star formation rate. By exploiting a unique combination of the largest, most homogeneous interferometric CO survey of galaxies to date (the Extragalactic Database for Galaxy Evolution, or EDGE) and one of the principal ongoing optical integral field unit (IFU) surveys (CALIFA), the project team will confront models of star formation and galaxy evolution with uniform, high quality measurements of gas masses and star formation rates, supplemented by a vast array of additional data, including star formation history, stellar mass, nuclear activity, and the metallicity and kinematics of the gas and stars. These studies will be conducted on a spatially resolved basis across a well-defined sample that is representative of the nearby Universe, and will thus inform future studies of star formation and mass assembly at all redshifts undertaken by JWST and ALMA.