Semi-empirical catalog of early-type galaxy-halo systems: dark matter density profiles, halo contraction and dark matter annihilation strength

With Sloan Digital Sky Survey galaxy data and halo data from up-to-date N-body simulations within the Lambda CDM framework we construct a semi-empirical catalog (SEC) of early-type galaxy-halo systems by making a self-consistent bivariate statistical match of stellar mass (M-*) and velocity dispersion (sigma) with halo virial mass (M-vir) as demonstrated here for the first time. We then assign stellar mass profile and velocity dispersion profile parameters to each system in the SEC using their observed correlations with M-* and sigma. Simultaneously, we solve for dark matter density profile of each halo using the spherical Jeans equation. The resulting dark matter density profiles deviate in general from the dissipationless profile of Navarro-Frenk-White or Einasto and their mean inner density slope and concentration vary systematically with M-vir. Statistical tests of the distribution of profiles at fixed M-vir rule out the null hypothesis that it follows the distribution predicted by dissipationless N-body simulations for M-vir less than or similar to 10(13.5-14.5) M-circle dot. These dark matter profiles imply that dark matter density is, on average, enhanced significantly in the inner region of halos with M-vir less than or similar to 10(13.5-14.5) M-circle dot supporting halo contraction. The main characteristics of halo contraction are: (1) the mean dark matter density within the effective radius has increased by a factor varying systematically up to approximate to 3-4 at M-vir = 10(12) M-circle dot, and (2) the inner density slope has a mean of approximate to 1.3 with rho(dm)(r) proportional to r(-alpha) and a halo-to-halo rms scatter of rms(alpha) similar to 0.4-0.5 for 10(12) M-circle dot less than or similar to M-vir less than or similar to 10(13-14) M-circle dot steeper than the NFW profile (alpha = 1). Based on our results we predict that halos of nearby elliptical and lenticular galaxies can, in principle, be promising targets for gamma-ray emission from dark matter annihilation.