X-ray measurements of the dark matter distribution in clusters of galaxies with Chandra

We investigate the dark matter distributions in the central region of two clusters of galaxies (A1835 and MKW3S) using Chandra data. N-body simulations in the standard cold dark matter (CDM) model predict the dark matter distribution shows a cuspy dark matter profile: p(r) proportional to r(alpha), with alpha in the range 1-2, while observations of dwarf and low surface brightness galaxies seem to favor the presence of a relatively flat core: 0 < alpha < 1. To investigate the dark matter distributions in the central region of clusters of galaxies. we analyze the Chandra data of A 1835 and MKW3S with a deprojection method. We derive the mass profiles without the assumption of analytical models. We examine the inner slope of derived mass profiles assuming the dark matter profile is described with a power-law expression. The values of the slope alpha are 0.95 +/- 0.10 for A1835 and 1.33 +/- 0.12 for MKW3S within the radius of 200 kpc. These are consistent with the result of the CDM simulations. However. within the radius of 100 kpc, the value of alpha is less than unity for A1835 (0.47 +/- 0.31). Our result implies that the central dark matter profile of some clusters cannot be described by CDM halos. (C) 2004 Published by Elsevier Ltd on behalf of COSPAR.