Central and Satellite Colors in Galaxy Groups: A Comparison of the Halo Model and SDSS Group Catalogs

TL;DR

This study compares galaxy color predictions from a halo model with actual SDSS group data, revealing that central galaxies are generally bluer than satellites at fixed luminosity but redder at fixed mass, with good overall agreement.

Contribution

It demonstrates the consistency of a halo-model-based prediction of galaxy colors with SDSS observations, highlighting the environmental dependence of galaxy color.

Findings

Central galaxies are bluer than satellites at fixed luminosity.

At fixed halo mass, centrals tend to be redder than satellites.

Model predictions agree well with SDSS data for most galaxy types.

Abstract

Current analytic and semi-analytic dark matter halo models distinguish between the central galaxy in a halo and the satellite galaxies in halo substructures. Using a recent halo-model description of the color dependence of galaxy clustering (Skibba & Sheth 2008), we investigate the colors of central and satellite galaxies predicted by the model and compare them to those of two galaxy group catalogs constructed from the Sloan Digital Sky Survey (Yang et al. 2007, Berlind et al. 2006a). In the model, the environmental dependence of galaxy color is determined by that of halo mass, and the predicted color mark correlations were shown to be consistent with SDSS measurements. The model assumes that satellites tend to follow a color-magnitude sequence that approaches the red sequence at bright luminosities; the model's success suggests that bright satellites tend to be `red and dead' while the star formation in fainter ones is in the process of being quenched. In both the model and the SDSS group catalogs, we find that at fixed luminosity or stellar mass, central galaxies tend to be bluer than satellites. In contrast, at fixed group richness or halo mass, central galaxies tend to be redder than satellites, and galaxy colors become redder with increasing mass. We also compare the central and satellite galaxy color distributions, as a function of luminosity and as a function of richness, in the model and in the two group catalogs. Except for faint galaxies and small groups, the model and both group catalogs are in very good agreement.