Merger Shocks in Galaxy Clusters A665 and A2163 and Their Relation to Radio Halos

We present Chandra gas temperature maps for two hot, intermediate-redshiftclusters A665 and A2163. Both show strong temperature variations in theircentral r=1 Mpc regions, naturally interpreted as product of the subclustermergers. The A665 map reveals a shock in front of the cool core, while thetemperature structure of A2163 is more complicated. On a larger linear scale,our data on A2163 indicate a radial temperature decline in agreement withearlier ASCA results, although the uncertainties are large. Both these clustersexhibit previously known synchrotron radio halos. Comparison of the radioimages and the gas temperature maps indicates that radio emission predominantlycomes from the hot gas regions, providing a strong argument in favor of thehypothesis that relativistic electrons are accelerated in merger shocks.