  We perform Halo Occupation Distribution (HOD) modeling to interpret
small-scale and intermediate-scale clustering of 35,000 luminous early-type
galaxies and their cross-correlation with a reference imaging sample of normal
L* galaxies in the Sloan Digital Sky Survey. The modeling results show that
most of these luminous red galaxies (LRGs) are central galaxies residing in
massive halos of typical mass M ~ a few times 10^13 to 10^14 Msun/h, while a
few percent of them have to be satellites within halos in order to produce the
strong auto-correlations exhibited on smaller scales. The mean luminosity Lc of
central LRGs increases with the host halo mass, with a rough scaling relation
of Lc \propto M^0.5. The halo mass required to host on average one satellite
LRG above a luminosity threshold is found to be about 10 times higher than that
required to host a central LRG above the same threshold. We find that in
massive halos the distribution of L* galaxies roughly follows that of the dark
matter and their mean occupation number scales with halo mass as M^1.5. The HOD
modeling results also allows for an intuitive understanding of the
scale-dependent luminosity dependence of the cross-correlation between LRGs and
L_* galaxies. Constraints on the LRG HOD provide tests to models of formation
and evolution of massive galaxies, and they are also useful for cosmological
parameter investigations. In one of the appendices, we provide LRG HOD
parameters with dependence on cosmology inferred from modeling the two-point
auto-correlation functions of LRGs.
