1. The overdensities of galaxy environments as a function of luminosity and color David W. Hogg Center for Cosmology and Particle Physics Department of Physics New York University

2. punch line For disk galaxies, it is star-formation history, and not mass, that is connected to environment.

3. overdensity Scale density to cosmic mean and subtract unity; mean environments have delta=0. We consider 2 different scales: –8/h Mpc redshift-angle space hard-edge spheres; and –1/h Mpc statistically deprojected from imaging in a spherical Gaussian window. The measures have low S/N, so we take means in overdensity at fixed galaxy properties.

4. overdensity depends on luminosity

5. overdensity depends on color

6. bivariate relations Overdensity depends on color and luminosity. Color depends on luminosity and vice versa (ie, more luminous galaxies are redder). Can we separate the color and luminosity effects?

7. the color-magnitude diagram

8. overdensity vs luminosity and color

10. conclusions Environmental overdensity depends on both color and magnitude. “All” galaxy populations are clustered. The most luminous (ie, massive) red galaxies live in very high density regions For disk galaxies, star-formation history, not mass, is most closely related to environment.

12. the end