ChandraObservation of Abell 2065: An Unequal Mass Merger?

Abstract

We present an analysis of a 41 ks Chandra ACIS-I observation of the merging cluster Abell 2065. Previous ROSAT and ASCA observations provided evidence for an ongoing merger and suggested that there were two surviving cooling cores, which were associated with the two cD galaxies at the center of the cluster. The Chandra observation reveals only one X-ray surface brightness peak. Its gas is cool and displaced slightly from the more luminous, southern cD galaxy. Combined with the surface brightness profile, this suggests that this cool material has formed a cold front. In the higher spatial resolution Chandra image, the second feature to the north is not associated with the second cD; rather, it appears to be a trial of gas behind the main cD. We argue that only one of the two cooling cores has survived the merger. The survival of the cool core constrains the merger kinematics, placing an upper limit of 1900 km s-1 on the relative merger velocity. A surface brightness discontinuity, found at ~140 kpc from the southern cD, has a Mach number of 1.66; the nature of the discontinuity (shock or cold front) is not clear fron the data. We argue that Abell 2065 is an unequal mass merger. The more massive southern cluster has driven a shock into the ICM of the infalling northern cluster, which has disrupted the cool core of the latter. We estimate that core crossing occurred a few hundred Myr ago, probably for the first time.