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 H 0 of 77 +19 -15 km s -1 Mpc -1 (1 errors) for an Einstein-de Sitter universe, or 85 +20 -17 km s -1 Mpc -1 for a flat model with = 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.