Ryan Hennessy

Application of a Self-Similar Pressure Profile to Sunyaev-Zel'Dovich Effect Data from Galaxy Clusters

We investigate the utility of a new, self-similar pressure profile for fitting Sunyaev–Zel’dovich (SZ) effect observations of galaxy clusters. Current SZ imaging instruments–such as the Sunyaev–Zel’dovich Array (SZA)– are capable of probing clusters over a large range in a physical scale. A model is therefore required that can accurately describe a cluster’s pressure profile over a broad range of radii from the core of the cluster out to a significant fraction of the virial radius. In the analysis presented here, we fit a 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: A1835, A1914, and CL J1226.9+3332. From the joint analysis of the SZ and X-ray data, we derive physical properties such as gas mass, total mass, gas fraction and the intrinsic, integrated Compton y-parameter. We find that parameters derived from the joint fit to the SZ and X-ray data agree well with a detailed, independent X-ray-only analysis of the same clusters. In particular, we find that, when combined with X-ray imaging data, this new pressure profile yields an independent electron radial temperature profile that is in good agreement with spectroscopic X-ray measurements.

RADIO SOURCES FROM A 31 GHz SKY SURVEY WITH THE SUNYAEV-ZEL'DOVICH ARRAY

We present the rst sample of 31-GHz selected sources to ux levels of 1 mJy. From late 2005 to mid 2007, the Sunyaev-Zel’dovich Array (SZA) observed 7.7 square degrees of the sky at 31 GHz to a median rms of 0:18 mJy=beam. We identify 209 sources at greater than 5 signicance in the 31 GHz maps, ranging in ux from 0.7 mJy to 200 mJy. Archival NVSS data at 1.4 GHz and observations at 5 GHz with the Very Large Array are used to characterize the sources. We determine the maximumlikelihood integrated source count to be N (>S ) = (27:2 2:5 ) deg 2 (SmJy) 1:18 0:12 over the ux range 0 :7 15 mJy. This result is signicantly higher than predictions based on 1.4-GHz selected samples, a discrepancy which can be explained by a small shift in the spectral index distribution for faint 1.4 GHz sources. From comparison with previous measurements of sources within the central arcminute of massive clusters, we derive an overdensity of 6:8 4:4, relative to eld sources. Subject headings: techniques: interferometric, catalogs, surveys, cosmology: cosmic microwave background, cosmology: observations, radio continuum: general