The Sunyaev-Zel'dovich Array: Constraining a new pressure profile for fitting SZE observations of galaxy clusters

The Sunyaev-Zel'dovich Array (SZA), an eight element interferometer designed to probe the Sunyaev-Zel'dovich effect (SZE) from galaxy clusters, which I helped construct and operate, is described here (Part I). I then use SZA observations to investigate the utility of a new, self-similar pressure profile for fitting SZE observations of galaxy clusters (Part II). The SZA 30-GHz receiver system probes angular scales ~1-5'. A model that can accurately describe a cluster's pressure profile over a correspondingly broad range of radii is therefore required. In the analysis presented here, I fit a 2-parameter, radial pressure profile, derived from simulations and detailed X- ray analysis of relaxed clusters, to SZA observations of three clusters with exceptionally high quality X-ray data. From the joint analysis of the SZE and X-ray data, I derive physical properties of the cluster, such as gas and total mass, gas fraction and the integrated Compton y -parameter. The parameters derived from the joint fit to SZE+X-ray data agree well with a detailed, independent, X-ray-only analysis of these same clusters. When combined with X-ray imaging data, this new pressure profile yields an independent estimate of the electron temperature profile that is in good agreement with spectroscopic X-ray determinations. In addition to yielding relationships between cluster observables and physical cluster properties, this model could prove to be a useful tool in helping to constrain the temperatures of high redshift clusters, for which X-ray spectroscopic data are difficult to obtain.