2004ApJ...615..181H

We present a mosaic of XMM-Newton observations of the nearby major-merger cluster A754 that has either a wider field or better spectral or spatial resolution than previous observations. We construct maps of X-ray surface brightness and temperature integrated along the line of sight. From these two primary maps we derive pseudopressure and pseudoentropy maps. There is structure on a large range of scales in these maps, but the basic pattern is similar to numerical hydrodynamic simulations of cluster mergers. The high surface brightness eastern bar contains gas with the minimum entropy and temperature coupled with the highest iron abundance and density in the cluster. A new feature revealed by these observations is a plumelike structure that appears to emerge from the bar heading northwest. The diffuse radio source also occupies this region, and there is some correspondence between the two. Another new feature is a rim of hot gas to the east, south, and west. We interpret the bar as the core gas from the original main cluster flattened and displaced from the dark matter potential minimum by the merger. The hot rim is the outgoing forward shock from the merger. However, this and previous shocks were weak (M≤2.25), so they are likely only small contributors to the radio-emitting particles. These observations lend support to the merger hypothesis in A754, but some of the parameters of existing models need modification.