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Session 52 - Clusters & Cosmology.
Oral session, Thursday, June 12
North Main Hall C/D,
We report here on X-ray and optical observations of a newly discovered cluster of galaxies, 1E 0657-56. Optical observations of an unidentified, extended Einstein X-ray source revealed the presence of a cluster of galaxies with a redshift z = 0.30, and a background gravitational arc at an undetermined redshift. X-ray data obtained with the ROSAT HRI and ASCA suggest that 1E 0657-56 is a highly luminous cluster in which a merger of subclusters is occurring. The temperature of the hot gas in 1E0657 is 14 keV, which places it in a select class of two with the cluster A2163 (Arnaud et al. 1992). As emphasized by Arnaud et al (1992) and Hattori (1994), the existence of one or more clusters with a gas temperature in excess of 10 keV has important implications for the cosmological theory of origin of clusters of galaxies, because large initial density fluctuations are required.