The density profiles of the dark matter halo are not universal

We perform a series of high-resolution N-body simulations designed to exami ne the density profiles of dark matter halos. From 12 simulated halos rangi ng in mass from 2 x 10(12) to 5 x 10(14) h(-1) M., (represented by similar to 1 million particles within the virial radius), we find a clear systemati c correlation between the halo mass and the slope of the density profile at 1% of the virial radius, in addition to the variations of the slope among halos of similar mass. More specifically, the slope is similar to-1.5, -1.3 , and -1.1 for galaxy-, group-, and cluster-mass halos, respectively. While we confirm the earlier simulation results that the inner slope is steeper than the universal profile originally proposed by Navarro, Frenk, & White, this mass dependence is inconsistent with several analytical arguments atte mpting to link the inner slope with the primordial index of the fluctuation spectrum. Thus, we conclude that the dark matter density profiles, especia lly in the inner region, are not universal.