CLUSTERING PROPERTIES AND HALO MASSES FOR CENTRAL GALAXIES IN THE LOCAL UNIVERSE

Abstract

ABSTRACT We investigate the clustering and dark matter halo mass for a sample of ∼16,000 central galaxies selected from the SDSS/DR7 group catalog. We select subsamples of central galaxies on three two-dimensional planes, each formed by stellar mass (M * ?> ) and one other property out of optical color (g − r), surface stellar mass density ( &mgr; * ?> ), and central stellar velocity dispersion ( &sgr; * ?> ). For each subsample we measure both the projected cross-correlation function ( w p ( r p ) ?> ) relative to a reference galaxy sample, and an average mass of the host dark matter halos (M h ?> ). Both w p ( r p ) ?> and M h ?> show the strongest dependence on M * ?> , and there is no clear dependence on the other properties when M * ?> is fixed. This result provides strong support to the previously adopted assumption that, for central galaxies, stellar mass is the best indicator of the host dark halo mass. For comparison we have estimated w p ( r p ) ?> for the full galaxy population and the population of satellite galaxies. Both populations show similar clustering properties in all cases, but they are similar to the centrals only at high masses (M * ?> ≳ 10 11 ?> M ⊙ ?> ). At lower masses, their w p ( r p ) ?> depends more strongly on &sgr; * ?> and g − r than on M * ?> . It is thus necessary to consider central and satellite galaxies separately when studying the link between galaxies and dark matter halos. We discuss the implications of our results for the relative roles of halo mass and galaxy structure in quenching the star formation in central galaxies.