The Structure of Cold Dark Matter Halos

We investigate the internal structure of cold dark matter halos using high resolution N-body simulations. As the mass and force resolution are increased, halo density profiles become steeper, asymp-toting to a slope of ∼ −4/3 in the central regions and may not have converged to a unique result. At our highest resolution we have nearly 3 million particles within the virial radius, R 200 , and force softening that is ∼ 0.2%R 200. This resolution has also allowed us to resolve a large part of the overmerging problem-we find over 1000 surviving dark halos orbiting within a single cluster potential. These data have given us unprecedented insights into the dynamics and structure of " halos within halos " , allowing us for the first time, to compare the distribution of dark matter with observations of galaxies in clusters.