MODELING THE VERY SMALL SCALE CLUSTERING OF LUMINOUS RED GALAXIES

We model the small-scale clustering of luminous red galaxies (LRGs) in the Sloan Digital Sky Survey. Specifically, we use the halo occupation distribution formalism to model the projected two-point correlation function of LRGs on scales well within the sizes of their host halos (0.016 h(-1) Mpc <= r <= 0.42 h(-1) Mpc). We start by varying P(N vertical bar M), the probability distribution that a dark matter halo of mass M contains N LRGs, and assuming that the radial distribution of satellite LRGs within halos traces the Navarro-Frenk-White (NFW) dark matter density profile. We find that varying P(N vertical bar M) alone is not sufficient to match the small-scale data. We next allow the concentration of satellite LRG galaxies to differ from that of dark matter and find that this is also not sufficient. Finally, we relax the assumption of an NFW profile and allow the inner slope of the density profile to vary. We find that this model provides a good fit to the data and the resulting value of the slope is -2.17 +/- 0.12. The radial density profile of satellite LRGs within halos is thus not compatible with that of the underlying dark matter, but rather is closer to an isothermal distribution.