STELLAR MASS VERSUS STELLAR VELOCITY DISPERSION: WHICH IS BETTER FOR LINKING GALAXIES TO THEIR DARK MATTER HALOS?

Abstract

It was recently suggested that compared to its stellar mass (M*), the central stellar velocity dispersion (σ*) of a galaxy might be a better indicator for its host dark matter halo mass. Here we test this hypothesis by estimating the dark matter halo mass for central galaxies in groups as a function of M* and σ*. For this we have estimated the redshift-space cross-correlation function (CCF) between the central galaxies at given M* and σ* and a reference galaxy sample, from which we determine both the projected CCF, wp(rp), and the velocity dispersion profile. A halo mass is then obtained from the average velocity dispersion within the virial radius. At fixed M*, we find very weak or no correlation between halo mass and σ*. In contrast, strong mass dependence is clearly seen even when σ* is limited to a narrow range. Our results thus firmly demonstrate that the stellar mass of central galaxies is still a good (if not the best) indicator for dark matter halo mass, better than the stellar velocity dispersion. The dependence of galaxy clustering on σ* at fixed M*, as recently discovered by Wake et al., may be attributed to satellite galaxies, for which the tidal stripping occurring within halos has stronger effect on stellar mass than on central stellar velocity dispersion.