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[58.06] The SZ Effect Signature of Excess Entropy in Distant Galaxy Clusters

I. G. McCarthy, A. Babul (Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canada), G. P. Holder (School of Natural Sciences, Institute for Advanced Study, Princeton, NJ, 08540, USA), M. L. Balogh (Department of Physics, University of Durham, South Road, Durham, DH1 3LE, UK)

X-ray observations of an ``entropy floor'' in nearby groups and clusters of galaxies offer strong evidence that important non-gravitational processes, such as radiative cooling and/or ``preheating'', have significantly influenced the evolution of the intracluster medium (ICM). For the first time, we use the Sunyaev-Zeldovich (SZ) effect to test this hypothesis and estimate the level of the entropy floor in galaxy clusters. A detailed comparison of a number of predicted SZ effect scaling relations with the largest compilation of high redshift SZ effect observational data to date indicates that the presence of an entropy floor is favored by the SZ effect data and that the inferred level of the floor (K₀ > 300 keV cm²) is comparable to that found in studies of X-ray scaling relations of nearby massive clusters (which also require K₀ > 300 keV cm²). In addition, we find no evidence for evolution of the entropy floor level out to z ~0.7.

I. G. M. is supported by a postgraduate scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC).

The author(s) of this abstract have provided an email address for comments about the abstract: mccarthy@beluga.phys.uvic.ca

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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.