Revealing velocity dispersion as the best indicator of a galaxy’s color, compared to stellar mass, surface mass density, or morphology

Using data of nearby galaxies from the Sloan Digital Sky Survey we investigate whether stellar mass (Mstar), central velocity dispersion (σ ), surface mass density (Σ), or the Sérsic n parameter is best correlated with a galaxy’s rest-frame color. Specifically, we determine how the mean color of galaxies varies with one parameter when another is fixed. When Mstar is fixed we see that strong trends remain with all other parameters, whereas residual trends are weaker when Σ, n, or σ is fixed. Overall σ is the best indicator of a galaxy’s typical color, showing the largest residual color dependence when any of the other three parameters are fixed, and Mstar is the poorest. Other studies have indicated that both the central black hole mass and possibly host dark matter halo properties (mass or concentration) are also better correlated with σ than with Mstar, Σ, or n. Therefore, it could be the case that the strong correlation between color and σ reflects an underlying relationship between a galaxy’s star formation history and/or present star formation rate and the properties of its dark matter halo and/or the feedback from its central supermassive black hole.