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J. C. Kempner, L. P. David, J. M. Vrtilek (Smithsonian Astrophysical Observatory)
We present a 25 ksec Chandra observation of the merging cluster of galaxies Abell 2744. The cluster has one of the most luminous radio halos known, a powerful radio relic, and a bimodal galaxy distribution in redshift space. All of these characteristics provide strong evidence for an on-going major merger. While studies with lower resolution X-ray imagers have shown an obvious second peak in the ICM, the high resolution of Chandra enables us to show that this other peak is actually a small subcluster beginning to fall into the main cluster. It is much too small and is at too great a distance from the main cluster to be the cause of the radio halo or to contribute many galaxies to the observed population. The cold core of the subcluster has a well-defined leading edge and bow shock. The Chandra data also show a great deal of substructure in the main cluster both in brightness and in temperature, including evidence for several merger shocks. This substructure, combined with the galaxy velocities and the large luminosity of the halo, suggests that the cluster is undergoing a relatively symmetric merger between two massive clusters. From the temperature structure and the galaxy distribution, we conclude that the two merging subclusters are near core passage, probably on their initial approach.
Support for this work was provided by the National Aeronautics and Space Administration through Chandra Award Number GO2-3171X issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-39073.
Bulletin of the American Astronomical Society,
© 2003. The American Astronomical Soceity.