A measurement of H0 from Ryle Telescope, ASCA and ROSAT observations of Abell 773

Abstract

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 HQ of 77-15+19 km s-1 Mpc-1 (1σ errors) for an Einstein - de Sitter universe, or 85-17+20 km s-1 Mpc-1 for a flat model with ΩA = 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.