Chandra Observations of A2670 and A2107: A Comet Galaxy and cDs with Large Peculiar Velocities

Abstract

We present an analysis of Chandra observations of the galaxy clusters A2670 and A2107. Their cD galaxies have large peculiar velocities (>200km/s) and thus the clusters appear to be undergoing mergers. In A2670, we find a comet-like structure around one of the brightest galaxies. At the leading edge of the structure, there is a cold front. The mass of the X-ray gas in the comet-like structure suggests that the galaxy was in a small cluster or group, and its intracluster medium (ICM) is being stripped by ram-pressure. The regions of cool interstellar medium (ISM) of the cD galaxies in A2670 and A2107 are very compact. This is similar to the brightest galaxies in the Coma cluster, which is also a merging cluster. In each galaxy, the short cooling time of the ISM requires a heating source; the compact nature of the ISM makes it unlikely that the heating source is a central active galactic nucleus (AGN).Comment: PASJ in pres