CfA OIR Division Lunch Talks
Friday, November 12, 2010, Noon, Phillips Auditorium

Role of Environment and Self-regulation in Galaxy Evolution at 1 < z < 4
Dr. Adam Muzzin (Yale)

Studies of the local universe have shown that almost any parameter we use to describe a galaxy - color, age, size, morphology, metallicity - is correlated with both its mass and environment. In principle, similar measurements at high redshift could distinguish the physical processes responsible for these correlations; however, high-redshift field galaxy surveys have produced conflicting results about the roles of mass and environment in galaxy evolution. I will present a new attempt to understand this problem using distant galaxy clusters, the most extreme high-density environments in the universe. The Gemini Cluster Astrophysics Spectroscopic Survey (GCLASS) is a 220-hour spectroscopic program using the Gemini North and South telescopes that provides highly complete spectroscopy for 10 rich clusters at z ~ 1. Initial results from GCLASS suggest that even in clusters, massive galaxy formation is primarily a self-regulated process, with environment playing only a supporting role. I will also discuss results from the NEWFIRM Medium Band Surveys that show that massive galaxies exist in less dense environments up to z ~ 2 - 4 and still display a clear bi-modality, further supporting the self-regulation hypothesis.