Citation:
Date Published:
December 1, 2009Abstract:
We perform halo occupation distribution (HOD) modeling to interpretsmall-scale and intermediate-scale clustering of 35,000 luminousearly-type galaxies and their cross-correlation with a reference imagingsample of normal L * galaxies in the Sloan Digital SkySurvey. The modeling results show that most of these luminous redgalaxies (LRGs) are central galaxies residing in massive halos oftypical mass M~ a few times 1013-1014 h-1 M sun, while a few percent of them have to besatellites within halos in order to produce the strong auto-correlationsexhibited on smaller scales. The mean luminosity Lc ofcentral LRGs increases with the host halo mass, with a rough scalingrelation of Lc vprop M 0.5. The halo mass requiredto host on average one satellite LRG above a luminosity threshold isfound to be about 10 times higher than that required to host a centralLRG above the same threshold. We find that in massive halos thedistribution of L * galaxies roughly follows that of the darkmatter and their mean occupation number scales with halo mass as M1.5. The HOD modeling results also allow for an intuitiveunderstanding of the scale-dependent luminosity dependence of thecross-correlation between LRGs and L * galaxies. Constraintson the LRG HOD provide tests for models of formation and evolution ofmassive galaxies, and they are also useful for cosmological parameterinvestigations. In one of the appendices, we provide LRG HOD parameterswith dependence on cosmology inferred from modeling the two-pointauto-correlation functions of LRGs.