AAS 207th Meeting, 8-12 January 2006
Session 190 Galaxy Clusters at z $>$ 0.5
Oral, Thursday, 10:00-11:30am, January 12, 2006, Maryland

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[190.06] Star Formation and the Butcher-Oemler effect in Intermediate Redshift Clusters

S. M. Crawford, M. A. Bershady, J. G. Hoessel (University of Wisconsin--Madison)

The Butcher-Oemler effect, the increasing population of blue galaxies in galaxy clusters with redshift, has been confirmed through extensive photometric and spectroscopic studies, but strong variations are seen between clusters even at similar redshifts. Furthermore, the total star formation, measured via several different methods, occurring in a small sample of intermediate redshift clusters displays trends with redshift, mass, and X-ray luminosity. We present narrow-band observations from the WIYN 3.5m telescope of six intermediate redshift (0.5 < z < 0.9) galaxy clusters to measure the total star formation in these rich clusters. These observations almost double the number of measurements of star formation occurring in intermediate redshift clusters and give a consistent measurement of un-obscured star formation through the OII[\lambda 3727] emission line down to 0.1 M\odot/yr. We investigate any trends seen between the clusters total star formation and its properties such as mass, luminosity, redshift, and virialization. We quantify the virialization through the luminosity gap statistic, the asymmetry of the galaxy distribution, and the offset from the Tx- \sigma relationship for each cluster. The recent merger history in galaxy clusters is one explanation for the excess in blue galaxies seen in some clusters. This work was supported by HST ARCHIVE grant #9917, NSF grant AST-0307417, and an award from the Wisconsin Space Grant Corportation.

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