X‐Ray Properties of the Abell 644 Cluster of Galaxies

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Abstract
We use new ASCA observations and archival ROSAT PSPC data to determine the X-ray spectral properties of the intracluster gas in Abell 644. From the overall spectrum, we determine the average gas temperature to be 8.64 keV and an abundance of 0.32 ± 0.04 Z☉. The global ASCA and ROSAT spectra imply a cooling rate of 214 M☉ yr-1. The PSPC X-ray surface brightness profile and the ASCA data suggest a somewhat higher cooling rate. We determine the gravitational mass and gas mass as a function of radius. The total gravitating mass within 1.2 Mpc is 6.2 × 1014 M☉, of which 20% is in the form of hot gas. There is a region of elevated temperature 15-5' to the west of the cluster center. The south-southwest region of the cluster also shows excess emission in the ROSAT PSPC X-ray image, aligned with the major axis of the optical cD galaxy in the center of the cluster. We argue that the cluster is undergoing or has recently undergone a minor merger. The combination of a fairly strong cooling flow and evidence for a merger make this cluster an interesting case to test the disruption of cooling flow in mergers.
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