An X‐Ray Temperature Map of the Merging Cluster Abell 2255

We present a spatially resolved map of intracluster gas temperatures in therich cluster Abell 2255, using ROSAT PSPC data. The intracluster gas isstrongly non-isothermal and the temperature distribution supports theconclusions of Burns et al. (1995) that Abell~2255 is currently undergoing amerger. The hottest regions are near the core, northwest of the center. A mapof the ratio of softer to harder X-ray photons reveals an anomalously softregion northeast of the center, coincident with a radio ridge discovered byBurns et al (1995). We suggest that this cooler region is associated with aninfalling group of galaxies which is giving rise to the radio ridge. Meanwhile,a much more substantial recent merger between comparably sized subclustercomponents can account for the more global merger signatures, which include theextensive central radio halo, the large scale gas temperature variations, thepair of central dominant ellipticals, elliptical X-ray isophotes offset fromthese dominant galaxies, and the very high velocity dispersion of galaxies inthe cluster.Comment: 11 pages, LaTex, 4 figures, Accepted Astrophysical Journal 492, January 199