The Density Profile of Cluster-scale Dark Matter Halos

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 \rho(r) with an arbitrary r -> 0 slope \alpha. The data are well fitted by such a model with a central cusp with \alpha ~ 0.9 - 1.6 (68% confidence interval). For the standard-NFW case \alpha = 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 1\sigma upper limit for the core radius corresponds to a limit \sigma_star \leq 0.1 cm^2 g^-1 on the elastic collision cross-section in a self-interacting dark matter model.Comment: 4 pages, 3 figures; version accepted for publication by ApJ Letters. Three figures omitted to allow space for new fig. 3 and expanded results and discussion sections, including NSIS model fi

Optical Photometry of GRB 021004 : The First Month

Original article can be found at: http://www.iop.org/EJ/journal/aj Copyright American Astronomical Society DOI: 10.1086/374235 [Full text of this article is not available in the UHRA]Peer reviewe