Search

We have observed the Sunyaev–Zel'dovich (SZ) effect in a sample of five moderate-redshift clusters with the Ryle Telescope, and used them in conjunction with X-ray imaging and spectral data fromROSATandASCAto measure the Hubble constant. This sample was chosen with a strict X-ray flux limit using both the Bright Cluster Sample and the NorthernROSATAll-Sky Survey (RASS) cluster catalogues to be well above the surface brightness limit of the RASS, and hence to be unbiased with respect to the orientation of the cluster. This controls a major potential systematic effect in the SZ/X-ray method of measuringH0. Taking the weighted geometric mean of the results and including the main sources of error, namely the noise in the SZ measurement, the uncertainty in the X-ray temperatures and the unknown ellipticity and substructure of the clusters, we findassuming a standard cold dark matter model withorif. [ABSTRACT FROM AUTHOR]

We present new Ryle Telescope (RT) observations of the Sunyaev-Zel'dovich (SZ) decrement from the cluster Abell 773. The field contains a number of faint radio sources that required careful subtraction. We use ASCA observations to measure the gas temperature and a ROSAT HRI image to model the gas density distribution. Normalizing the gas distribution to fit the RT visibilities returns a value of H[sub 0] of 77[sup +19, sub -15] km s[sup -1] Mpc[sup -1] (1σ errors) for an Einstein-de Sitter universe, or 85[sup +20, sub -17] km[sup -1] Mpc[sup -1] for a flat model with Ω[sub Λ] = 0.7. The errors quoted include estimates of the effects of the principal errors: noise in the SZ measurement, gas temperature uncertainty and line-of-sight depth uncertainty. [ABSTRACT FROM AUTHOR]

Describes a maximum-likelihood approach to removing radio sources from observations of the Sunyaev-Zel'dovich effect. Removal of contaminating radio sources; Cosmology; Galaxies.