Wilkinson Microwave Anisotropy ProbeConstraints on the Intracluster 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 overall amplitude for the SZ signal at the 8 level, yielding a combined constraint of fgash 0:08 0:01(ran) 0:01(sys) on the gas mass fraction of the intracluster 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 2 level, while both show an increasing trend with X-ray temperature. Nevertheless, our SZ estimated gas fraction is 30%–40 % smaller than the concordance CDM cosmic average. We also express our observations in terms of the SZ flux–temperature relation and compare it with other observations, as well as with numerical studies. Based on its spectral and spatial signature, we can also extract the microwave point-source signal of the clusters at the 3 level, which puts the average microwave luminosity (at 41GHz)ofbrightcluster members (MK 21) at (2:4 0:8) ; 1027 h 2 ergs s 1 Hz 1. Furthermore, we can constrain the average dark matter halo concentration parameter to cvir 3:4þ0:6 0:9 for clusters with TX> 5 keV. Our work serves as an example for how correlation of SZ surveys with cluster surveys at other frequencies can significantly increase our physical understanding of the intracluster medium. Subject headinggs: cosmic microwave background — dark matter — diffuse radiation —