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Session 37 - X-ray Clusters: Implications for Cosmology.
Display session, Tuesday, June 09
Atlas Ballroom,

[37.05] The Butcher-Oemler Effect in Three Bimodal X-Ray Clusters

A. J. Metevier (UC Santa Cruz), A. K. Romer (Carnegie Mellon U.), M. P. Ulmer (Northwestern U.)

We present the results of a Butcher-Oemler-style analysis of three clusters at low redshift. These clusters exhibit bimodality in their X-ray surface brightnesses, and we have found that they all have higher fractions of blue galaxies (f_bs) than would be expected from Butcher and Oemler's (1984) study of centrally condensed clusters. This implies that star formation is occurring in a high fraction of the galaxies in our clusters. We believe that our results support the theory that star formation can be induced by shocks in the intracluster medium. We propose that the ``Butcher-Oemler effect" therefore reflects an enhanced rate of subclustering in the past.

Program listing for Tuesday