Dependence of galaxy stellar populations on density at z=0.3--1.5

I investigate the evolution of galaxy clustering and dependence on environment by comparing galaxies' spatial correlation lengths with their photometrically-determined spectral energy distribution (SED) types. This complements work on the density-morphology relation and expands our understanding of galaxy evolution at high redshifts (z < 1.5).;I first report on 1141 galaxies from the Spectroscopic Photometric Infrared-Chosen Extragalactic Survey (SPICES). The SPICES spectroscopy is used to judge the effectiveness of photometric star-galaxy separation and redshifts. Hubble Space Telescope imaging provides visual morphologies of the galaxies for comparing the density-morphology relation to the density-SED relation. Spatial correlation function amplitudes are determined for each galaxy individually, as are SED-types based on spectral template fitting, and the two are compared to produce a density-SED relation. As expected from the density-morphology relation, galaxies with early SED-types are shown to be substantially more prevalent than galaxies with late SED-types in high density regions.;I then report on 41,837 galaxies from the FLAMINGOS Extragalactic Survey (FLAMEX), extending the techniques developed in the SPICES survey to examine the density-SED relation and its redshift dependence for a much larger sample. The results indicate that the density-SED relation is already established by z = 1.5, with no substantive evolution between that epoch to the present, and that the relation is in place prior to cluster assembly. I also investigate how clustering differs for extremely red objects (EROs) versus non-ERO galaxies and for L > L* versus L > .6L* galaxies, and I compare the spatial correlation lengths for specific clusters to the cluster detection significance.;Finally, I present a separate project on the dissipation rates of open star clusters within our own galaxy. Studying the age distribution of the complete sample of 997 clusters for which age values are available, I propose that clusters are disrupted by at least three different mechanisms acting on different timescales: a long-term mechanism that produces a cluster half-life of 354 +/- 13 million years, a medium-term mechanism with a cluster half-life of 105 +/- 30 million years, and a short-term mechanism with a cluster half-life of 5.0 +/- .8 million years. I also estimate that 220 +/- 70 clusters are formed per ten million years within our current limits of observation.