AAS 202nd Meeting, May 2003
Session 51 Galaxy Clusters in the Sloan Digital Sky Survey
Special Oral, Thursday, May 29, 2003, 10:00-11:30am, 205/206

## [51.03] The overdensities of galaxy environments as a function of luminosity and color

D. W. Hogg (NYU), SDSS Collaboration

We study the mean environments of galaxies in the Sloan Digital Sky Survey as a function of rest-frame luminosity and color. Overdensities in galaxy number are estimated in 8\,h-1~\mathrm{Mpc} and 1\,h-1~\mathrm{Mpc} spheres centered on 115,000 galaxies taken from the SDSS spectroscopic sample. We find that, at constant color, overdensity is independent of luminosity for galaxies with the blue colors of spirals. This suggests that, at fixed star-formation history, spiral-galaxy mass is a very weak function of environment. Overdensity does depend on luminosity for galaxies with the red colors of early types; both low-luminosity and high-luminosity red galaxies are found to be in highly overdense regions. The dependences of mean overdensity on other galaxy properties are discussed; most other dependences are either weak or explained by the color and luminosity dependences.

This work was partially supported by NASA and NSF.

The author(s) of this abstract have provided an email address for comments about the abstract: david.hogg@nyu.edu

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