The Temperature Structure of 26 Nearby Clusters Observed with ASCA. Similarity of Temperature Profiles
Abstract
We present ASCA temperature profiles and, when possible, crude temperature maps for a sample of bright clusters with 0.04<z<0.09. Together with several previously published clusters, the sample includes A85, A119, A399, A401, A478, A754, A780, A1650, A1651, A1795, A2029, A2065, A2142, A2256, A2319, A2597, A3112, A3266, A3376, A3395, A3558, A3571, A3667, A4059, Cygnus A, and Triangulum Australis. About half of the sample shows evidence of merging in either temperature, entropy, or brightness maps. Nearly all clusters exhibit a significant radial temperature decline. For a typical 7 keV cluster, the temperature decline between 1 and 6 X-ray core radii (0.15 and 0.9/h Mpc) can be approximated by a polytropic index of 1.2-1.3. Assuming such a polytropic temperature profile, the gravitating mass within 1 and 6 core radii is 1.35 and 0.7 times the isothermal beta-model estimates, respectively. Most interestingly, we find that all temperature profiles (excluding those for the most asymmetric clusters) appear remarkably similar when the temperature is plotted against radius in units of the estimated virial radius. We compare the composite temperature profile to the published hydrodynamic simulations. The observed profiles appear steeper than those in most Lagrangian simulations (Evrard etal 1996; Eke etal 1997). The predictions for Omega=1 models are most discrepant, while models with low Omega are closer to our data. We note, however, that at least one Omega=1 Lagrangian simulation (Katz & White 1993) and the recent high-resolution Eulerian simulation (Bryan & Norman 1997) produced clusters with temperature profiles similar to those observed. Our results thus provide a constraint for testing numerical simulations and discriminating among models of cluster formation. (ABRIDGED)Keywords
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