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L Bai, G. H. Rieke, M. J. Rieke, J. L. Hinz, D. M. Kelly (Steward Observatory,, University of Arizona), K.-V. H. Tran (Institute for Astronomy, ETH Zurich, Switzerland)
Using MIPS observations and spectroscopically confirmed membership lists, we study the current star forming activity in two rich clusters: Coma at z=0.02 and MS 1054-03 at z=0.83. The shape of Coma's Infrared (IR) luminosity function (LF) is comparable to that of the field up to L~1044 erg/s; this suggests that at the current epoch, the global galaxy star formation rate (SFR) is generally independent of environment up to densities ~ 40 times greater than in field. However, the IR LF in Coma's core shows a shallower faint end slope and smaller L*IR, and there is a lack of very bright IR galaxies; these properties indicate that active star formation is depressed in very crowded regions. We compare our results on Coma to MS 1054-03, a cluster with an unusually high merger rate. We find that the MS1054 has slightly more high luminosity members but no strong evolution of the IR LF is indicated. This is in contrast to the strongly evolving field population. We also compare OII emission line strengths and infrared emissions of the cluster members as indicators of the SFR.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.