Modeling the Very Small-Scale Clustering of Luminous Red Galaxies
  We model the small-scale clustering of luminous red galaxies (LRGs; Masjedi
et al. 2006) in the Sloan Digital Sky Survey (SDSS). Specifically, we use the
halo occupation distribution (HOD) formalism to model the projected two-point
correlation function of LRGs on scales well within the sizes of their host
halos (0.016 Mpc/h < r < 0.42 Mpc/h). We start by varying P(N|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
NFW dark matter density profile. We find that varying P(N|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.
