Satellite kinematics - III. Halo masses of central galaxies in SDSS

Abstract

We use the kinematics of satellite galaxies that orbit around the central\ngalaxy in a dark matter halo to infer the scaling relations between halo mass\nand central galaxy properties. Using galaxies from the Sloan Digital Sky\nSurvey, we investigate the halo mass-luminosity relation (MLR) and the halo\nmass-stellar mass relation (MSR) of central galaxies. In particular, we focus\non the dependence of these scaling relations on the colour of the central\ngalaxy. We find that red central galaxies on average occupy more massive haloes\nthan blue central galaxies of the same luminosity. However, at fixed stellar\nmass there is no appreciable difference in the average halo mass of red and\nblue centrals, especially for M* $\\lsim$ 10^{10.5} h^{-2} Msun. This indicates\nthat stellar mass is a better indicator of halo mass than luminosity.\nNevertheless, we find that the scatter in halo masses at fixed stellar mass is\nnon-negligible for both red and blue centrals. It increases as a function of\nstellar mass for red centrals but shows a fairly constant behaviour for blue\ncentrals. We compare the scaling relations obtained in this paper with results\nfrom other independent studies of satellite kinematics, with results from a\nSDSS galaxy group catalog, from galaxy-galaxy weak lensing measurements, and\nfrom subhalo abundance matching studies. Overall, these different techniques\nyield MLRs and MSRs in fairly good agreement with each other (typically within\na factor of two), indicating that we are converging on an accurate and reliable\ndescription of the galaxy-dark matter connection. We briefly discuss some of\nthe remaining discrepancies among the various methods.\n