The heated core of the radio-quiet galaxy cluster A644.
BUOTE D.A., HUMPHREY P.J. and STOCKE J.T.
Abstract (from CDS):
We present an analysis of a Chandra ACIS-I observation of the massive galaxy cluster A644. This cluster was previously classified as a cooling flow, but no radio emission has been detected from its cD galaxy. Outside the core (R∼75 kpc∼0.03rvir) the hot ICM has properties consistent with a (relaxed) cool-core cluster out to the largest radii investigated (R∼415 kpc∼0.14rvir). Over this region the gravitating mass profile is described well by a Navarro-Frenk-White (NFW) profile with concentration parameter c=6.1±1.2 and virial radius rvir=2.9±0.4 Mpc. However, inside the core the temperature and entropy profiles reverse their inward radial decline and rise at the center; the inner temperature profile is inconsistent with a constant at the 2.3 σ level. Although the core region does not display X-ray cavities or filamentary structures characteristic of radio-loud, cool-core clusters, the peak of the X-ray emission is offset from that of the centroid of the global X-ray halo by ~60 kpc. The position of the cD galaxy lies approximately between the X-ray peak and centroid, further testifying to a merger origin for the properties of the X-ray emission in the core. We discuss the implications of A644 and the small number of radio-quiet, cool-core clusters for the AGN feedback paradigm to suppress cooling flows in clusters.