Chandra X-ray galaxy clusters at z < 1.4: Constraints on the inner slope of the density profiles

A reconstruction of the total mass (the fraction of dark matter, intercluster gas, and the brightest galaxy of the cluster) of 128 X-ray galaxy clusters at redshifts 0.01–1.4 based on Chandra observations is presented. The total mass M 200 and the baryonic mass M b have been measured for all the sample objects, as well as the concentration parameter c 200, which characterizes the size of the dark matter halo. The existence of a tight correlation between c 200 and M 200 is confirmed, c ∝ M vir /(1 + z) b with a = −0.56 ± 0.15 and b = 0.80 ± 0.25 (95% confidence level), in good agreement with the predictions of numerical simulations and previous observations. Fitting the inner dark-matter density slope α with a generalized NFW model yields α = 1.10 ± 0.48 at the 2σ confidence level, combining the results for the entire sample, for which the model gives a good description of the data. There is also a tight correlation between the inner slope of the dark-matter density profile α and the baryonic mass contentM b for massive galaxy clusters, namely, α decreases with increasing baryonic mass content. A simple power-law model is used to fit the α − M b distributions, yielding the break point for the inner slope of the dark-matter density profile b = 1.72 ± 0.37 (68% confidence level).