Density profiles and clustering of dark matter halos

The density profile and the clustering of dark matter (DM) halos are two very important ingredients for understanding many observations of galaxies. In this talk, I present our new results for these two quantities from a large set of high quality N-body simulations. We show that in an Einstein de Sitter Universe about 35 percent of the halos could not be fitted by the Navarro, Frenk & White (NFW) profile because of too significant substructures, another 50 percent with less substructures can be reasonably described by the NFW profile, and the rest with the least substructures can be fitted by the NFW profile very nicely. For the halos which can be reasonably or better fitted by the NFW profile, the probability distribution function of the concentration parameter $c$ could be well described by a lognormal function with a dispersion $\sigma=0.27$. The mean value of $c$ is quite close to that predicted by NFW, though it decreases with the increase of the substructures. Our clustering analysis shows a significantly stronger clustering for low mass halos than Mo & White predict. A formula is therefore presented for the two-point correlation function of halos which can fit our simulation results (both CDM models and scale-free clustering models) very accurately.