Spartan 1 X-ray observations of the perseus cluster. III. The distribution of iron in the intracluster gas

The Spartan 1 instrument has resolved the spatial and spectral distribution of the 1-10 keV X-ray emission from the Perseus cluster in a region extending 50′ (1.6 Mpc) from the center. The data were fitted with a spherically symmetric three-dimensional model which included separate components for the cooling flow, the extended cluster emission, and a possible point source located at NGC 1275. A careful study has been made of the abundance distribution of iron as a function of radius. We confirm the existence of a gradient where the best-fit central abundance is 0.77^+0.30_-0.38 times the solar value and the linear gradient is -1.10^+0.89_-2.24 Mpc^-1 (90% confidence for a single interesting parameter in both cases). Joint 90% confidence limits to the abundance parameters have been established, and the resulting limits to the abundance distribution have been applied to theoretical models of cluster structure and evolution. We find that our results are consistent with a gas-removal mechanism with enhanced efficiency at the cluster center such as ram-pressure stripping or thermal exaporation. Our results are also in agreement with cluster evolution models in which the initial density of primordial gas in the cluster formation region is high (≥ 10²⁸ g cm^-3). The integrated mass of iron out to a radius of 1.6 Mpc is about 3 × 10¹⁰ M_⊙, about 5 times smaller than that deduced from X-ray observations under the assumption of a constant abundance.