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Session 37 - X-ray Clusters: Implications for Cosmology.
Display session, Tuesday, June 09
Abell 963 (z = 0.2) is an X-ray luminous, centrally concentrated cluster of galaxies with a dominant central cD galaxy. A963 also has two large diametrically opposed gravitational arcs associated with it, for which the origin from a single background galaxy is still uncertain.
We will present the results from two observational programs on A963:
1) Redshifts have been obtained for a total of 79 objects in the field of A963, consisting of 56 clusters members, 21 galaxies which are either foreground or background, and 2 galactic stars. We have used a subset of 36 red cluster members, for which spectra were obtained during a single observing run, to determine the cluster velocity dispersion. We find a value of \sim1350 km s^-1 (+200,-150) for \sigma_r, the rest-frame radial velocity dispersion, which is similar to other known lensing clusters.
2) ROSAT HRI observations of A963 reveal the cluster X-ray gas to be centrally concentrated and ellipsoidal rather than spherical in shape. Preliminary values for the core radius, r_c, and the ellipticity, \epsilon, are \sim25'' and \sim0.25, respectively. While this ellipticity is less than that of the central cD galaxy, which has \epsilon = 0.5, the X-ray gas and the cD galaxy are aligned along the same axis.
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Program listing for Tuesday