The Density Profile of Cluster-scale Dark Matter Halos

Abstract

We measure the average gravitational shear profile of 6 massive clusters (M_vir ~ 10^15 M_sun) at z=0.3 out to a radius ~2h^-1 Mpc. The measurements are fitted to a generalized NFW-like halo model ρ(r) with an arbitrary r -> 0 slope α. The data are well fitted by such a model with a central cusp with α~ 0.9 - 1.6 (68% confidence interval). For the standard-NFW case α= 1.0, we find a concentration parameter c_vir that is consistent with recent predictions from high-resolution CDM N-body simulations. Our data are also well fitted by an isothermal sphere model with a softened core. For this model, our 1σupper limit for the core radius corresponds to a limit σ_star \leq 0.1 cm^2 g^-1 on the elastic collision cross-section in a self-interacting dark matter model.