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Session 17 - CMB Radiation, Cosmology and Gravity.
Oral session, Monday, June 08

[17.07] The Galaxy Cluster Baryon Fraction: Cluster Physics and Cosmology

L. Grego (Caltech), J. E. Carlstrom, G. Holder, A. Cooray, E. Reese, W. Holzapfel (U. of Chicago), M. K. Joy (NASA/MSFC), S. K. Patel (U. of Alabama, Huntsville)

We present measurements of the gas mass fraction in a sample of massive, distant galaxy clusters. We infer the gas masses from measurements of the Sunyaev-Zel'dovich effect, a spectral distortion imprinted on the Cosmic Microwave Background radiation as it passes through the hot, intracluster gas, and compare these gas masses to measurements of the clusters' total gravitational masses as measured with the gas temperatures and the virial theorem, and as implied by observed gravitational lensing. A cluster's gas mass fraction constitutes a lower limit to its baryon fraction. Since galaxy clusters are large systems, the cluster baryon fraction may be representative of the universal value, and these measurements used to constrain cosmological models.

We present the gas mass fraction as a function of redshift and of x-ray temperature, and discuss the implications of these results for cluster physics and for cosmology.

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Program listing for Monday