A detailed statistical analysis of the mass profiles of galaxy clusters
  The distribution of mass in the halos of galaxies and galaxy clusters has
been probed observationally, theoretically, and in numerical simulations. Yet
there is still confusion about which of several suggested parameterized models
is the better representation, and whether these models are universal. We use
the temperature and density profiles of the intracluster medium as measured by
X-ray observations of 11 relaxed galaxy clusters to investigate mass models for
the halo using a thorough Bayesian statistical analysis. We make careful
comparisons between two- and three-parameter models, including the issue of a
universal third parameter. We find that, of the two-parameter models, the NFW
is the best representation, but we also find moderate statistical evidence that
a generalized three-parameter NFW model with a freely varying inner slope is
preferred, despite penalizing against the extra degree of freedom. There is a
strong indication that this inner slope needs to be determined for each cluster
individually, i.e. some clusters have central cores and others have steep
cusps. The mass-concentration relation of our sample is in reasonable agreement
with predictions based on numerical simulations.
