Chandra observation of the core of the galaxy cluster AWM7

Abstract

We present results from a Chandra observation of the core region of the nearby X-ray bright galaxy cluster AWM7. There are blob-like substructures, which are seen in the energy band 2--10 keV, within 10 kpc (20'') of the cD galaxy NGC1129, and the brightest sub-peak has a spatial extent more than 4 kpc. We also notice that the central soft X-ray peak is slightly offset from the optical center by 1 kpc. These structures have no correlated features in optical, infrared, or radio band. Energy spectrum of the hard sub-peak indicates a temperature higher than 3 keV with a metallicity less than 0.3 solar, or a power-law spectrum with photon index 1.2. A hardness ratio map and a narrow Fe-K band image jointly indicate two Fe-rich blobs symmetrically located around the cD galaxy, with the direction perpendicular to the sub-peak direction. In larger scales (r<60 kpc), the temperature gradually drops from 4 keV to 2 keV toward the cluster center and the metal abundance rises steeply to a peak of 1.5 solar at r=7 kpc. These results indicate that a dynamical process is going on in the central region of AWM7, which probably creates heated gas blobs and drives metal injection.