ChandraObservation of Abell 2065: An Unequal Mass Merger?

We present an analysis of a 41 ks Chandra observation of the merging clusterAbell 2065 with the ACIS-I detector. Previous observations with ROSAT and ASCAprovided evidence for an ongoing merger, but also suggested that there were twosurviving cooling cores, which were associated with the two cD galaxies in thecenter of the cluster. The Chandra observation reveals only one X-ray surfacebrightness peak, which is associated with the more luminous, southern cDgalaxy. The gas related with that peak is cool and displaced slightly from theposition of the cD. The data suggest that this cool material has formed a coldfront. On the other hand, in the higher spatial resolution Chandra image, thesecond feature to the north is not associated with the northern cD; rather, itappears to be a trail of gas behind the main cD. We argue that only one of thetwo cooling cores has survived the merger, although it is possible that thenorthern cD may not have possessed a cool core prior to the merger. We use thecool core survival to constrain the kinematics of the merger and we find anupper limit of ~< 1900 km/s for the merger relative velocity. A surfacebrightness discontinuity is found at ~140 kpc from the southern cD; the Machnumber for this feature is ${\cal M} = 1.66^{+0.24}_{-0.32}$, although itsnature (shock or cold front) is not clear from the data. We argue that Abell2065 is an example of an unequal mass merger. The more massive southern clusterhas driven a shock into the ICM of the infalling northern cluster, which hasdisrupted the cool core of the latter, if one existed originally. We estimatethat core crossing occurred a few hundred Myr ago, probably for the first time.Comment: 15 pages, 10 figures, ApJ in pres