  ASCA and ROSAT X-ray data are used to obtain two-dimensional maps of the gas
temperature, pressure and specific entropy in the Triangulum Australis 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 cluster core, which approximately
corresponds to the adiabatic relation. An underdense gas sector, found in the
ROSAT cluster image eastward of the core, has a higher temperature than average
at that radius. At this higher temperature, the gas pressure in this region is
equal to that of the rest of the cluster at the same radius, but the specific
entropy of this gas is significantly higher (although the temperature
difference itself is only marginally significant). We speculate that the
existence of this region of underdense high-entropy gas, as well as the
adiabatic central temperature peak, indicate recent or ongoing heating of the
intergalactic medium in this cluster. The most probable source 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 simulations to the data.
