The dependence on environment of the color-magnitude relation of galaxies

The distribution in color and absolute magnitude is presented for 55,158 galaxies taken from the Sloan Digital Sky Survey in the redshift range $0.08<z<0.12$, as a function of galaxy number overdensity in a line-of-sight cylinder of transverse radius $1h^{-1}\mathrm{M}\mathrm{p}\mathrm{c}$. In all environments, bulge-dominated galaxies (defined to be those with radial profiles best fit with large S'ersic indices) form a narrow, well defined color–magnitude relation. Although the most luminous galaxies reside preferentially in the highest density regions, there is only a barely detectable variation in the color (zero-point) or slope of the color–magnitude relation ($<0.02 $\mathrm{m}\mathrm{a}\mathrm{g}$$in$^{0.1}[g-r]$or$[B-V]$). These results constrain variations with environmental density in the ages or metallicities of typical bulge-dominated galaxies to be under 20 percent.