Institute for Advanced Study Astrophysics Seminar

The abundance of heavy elements in the ISM of star-forming galaxies represents a fundamental metric of the galaxy formation process. This metallicity reflects the gas reprocessed by stars, and the metals returned to the ISM by supernova explosions. Furthermore, galaxies display universal correlations among luminosity, stellar mass, and metallicity. The form and evolution of these correlations as a function of redshift lend insight into the infall and outflow of gas in galaxies as they build up their stellar populations, and provide important constraints on the nature of star-formation "feedback," a crucial ingredient in models of galaxy formation. Here we present evidence, based on rest-frame optical spectroscopy of galaxies at z~1.0-2.5, that the physical conditions in star-forming regions at high redshift are qualitatively different from those in the local universe. These differences have implications for understanding galaxy metallicities and, perhaps more fundamentally, star formation, itself, during an important epoch when the properties of today's galaxy population were still in the process of coming into place.