Distribution of matter in clusters of galaxies

Abstract

We present observations of the Sunyaev-Zel'dovich effect in 5 clusters of galaxies with a Fourier synthesis telescope - the Australia Telescope. A synthesis telescope has the advantage of simultaneously imaging the discrete radio sources and the Sunyaev-Zel'dovich effect. Observations were made at 8.8 GHz and in an ultra-compact 122.4m array configuration. Extended emission either due to radio halo sources or a blend of weak radio sources below the detection threshold, limited our ability to detect the SZ effect. However, upper limits to the SZ effect obtained for the cluster MS2137-23 was useful in constraining the cluster gas temperature when combined with the X-ray measurements and gravitational lensing constraints. The advantages of a multi-wavelength analysis of cluster mass density distributions and the properties of the intra-cluster medium were demonstrated through the examples of MS2137-23 and Abell 2218. Both clusters possess a giant arc that constrains the cluster central mass. In the case of Abell 2218 where there is a large amount of good data available in various wave-bands, we combined gravitational lensing constraints, optical photometry, measurements of the Sunyaev-Zel'dovich effect, X-ray surface brightness and temperature to constrain the cluster potential. H₀ and test the usual assumptions of mass-follows- light and hydrostatic equilibrium.