HEATING OF THE INTRACLUSTER GAS IN THE TRIANGULUM-AUSTRALIS CLUSTER

ASCA and ROSAT X-ray data are used to obtain two-dimensional maps of t he gas temperature, pressure, and specific entropy in the Triangulum A ustralis cluster of galaxies. We find that this hot (T-e = 10.3 +/- 0. 8 keV) system probably has a temperature peak (T-e > 12 keV) at the cl uster core, which approximately corresponds to the adiabatic relation. An underdense gas sector, found in the ROSAT cluster image eastward o f the core, has a higher temperature than average at that radius. At t his higher temperature, the gas pressure in this sector is equal to th at of the rest of the cluster at the same radius, but the specific ent ropy of this gas is significantly higher (although the temperature dif ference itself is only marginally significant). We speculate that the existence of this region of underdense high-entropy gas, as well as th e adiabatic central temperature peak, indicate recent or ongoing heati ng of the intergalactic medium in this cluster. The most probable sour ce of such heating is a subcluster merger, for which the hydrodynamic simulations predict a qualitatively similar temperature structure. We point out that entropy maps can provide a physically meaningful way of diagnosing merging clusters and comparing the predictions of merger s imulations to the data.