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[51.01] Galaxy Properties as a Function of Environment

C.J. Miller, R.C. Nichol, P.L. Gomez, M. Bernardi (CMU), A.M. Hopkins, A.J. Connolly (Pitt), SDSS Collaboration

A fundamental goal of observational cosmology is to determine the spatial distribution of galaxies as a function of their physical properties. Such observations are required to place constraints on models of galaxy formation and evolution. We create a magnitude and volume-limited subset of galaxies in Sloan Digital Sky Survey and study how three specific properties depend on their local density: star-formation, bulge-to-disk light ratios, and the presence and/or power of an active nucleus. The star-formation is quantified using extinction corrected, aperture corrected and absorption corrected measurements of the Halpha spectral luminosity. The morphology is measured using a new and fast bulge-to-disk decomposition software, and the AGNs are identified optically with their power quantified via the OIII luminosity. We discuss in turn how each of these properties depends on the local galaxy density. We characterize local galaxy densities using nearest neighbor measurements, kernal density estimators, and via proximity to nearby galaxy clusters.

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.