2 00 5 WMAP constraints on the Intra - Cluster Medium

We devise a Monte-Carlo based, optimized filter match method to extract the thermal Sunyaev-Zel’dovich (SZ) signature of a catalog of 116 low-redshift X-ray clusters from the first year data release of the Wilkinson Microwave Anisotropy Probe (WMAP). We detect an over-all amplitude for the SZ signal at the ∼ 8σ level, yielding a combined constraint of fgash = 0.08 ± 0.01(ran) ± 0.01(sys) on the gas mass fraction of the Intra-Cluster Medium. We also compile X-ray estimated gas fractions from the literature for our sample, and find that they are consistent with the SZ estimates at the 2σ level, while both show an increasing trend with X-ray temperature. Nevertheless, our SZ estimated gas fraction is 30− 40% smaller than the concordance ΛCDM cosmic average. We also express our observations in terms of the SZ flux-temperature relation, and compare it with other observations, as well as numerical studies. Based on its spectral and spatial signature, we can also extract the microwave point source signal of the clusters at the 3σ level, which puts the average microwave luminosity (at ∼ 41 GHz) of bright cluster members (MK ≤ −21) at (2.4 ± 0.8) × 10herg/s/Hz . Furthermore, we can constrain the average dark matter halo concentration parameter to cvir = 3.4 +0.6 −0.9, for clusters with Tx > 5 keV. Our work serves as an example for how correlation of SZ surveys with cluster surveys in other frequencies can significantly increase our physical understanding of the intra-cluster medium. Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, MS-51, 60 Garden Street, Cambridge, MA 02138; [email protected] Princeton University Observatory, Princeton University, Princeton, NJ 08544 Department of Astronomy, University of Illinois, Urbana, IL 61801 School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK