Structure of Dark Matter Halos from Hierarchical Clustering

We investigate the structure of the dark matter halo formed in the cold darkmatter scenario using $N$-body simulations. We simulated 12 halos with the massof $6.6\times 10^{11}M_{\odot}$ to $8.0\times 10^{14}M_{\odot}$. In almost allruns, the halos have density cusps proportional to $r^{-1.5}$ developed at thecenter, which is consistent with the results of recent high-resolutioncalculations. The density structure evolves in a self-similar way, and isuniversal in the sense that it is independent of the halo mass and initialrandom realization of density fluctuation. The density profile is in goodagreement with the profile proposed by Moore et al. (1999), which has centralslope proportional to $r^{-1.5}$ and outer slope proportional to $r^{-3}$. Thehalo grows through repeated accretion of diffuse smaller halos. We argue thatthe cusp is understood as a convergence slope for the accretion of tidallydisrupted matter.Comment: 34 including 23 figures, revised version, accepted for publication in Ap