• galaxies: clusters: individual: A773;
  • cosmic microwave background;
  • cosmology: observations;
  • distance scale;
  • X-rays: general


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 H0 of 77+19−15 km s−1 Mpc−1 (1σ errors) for an Einstein–de Sitter universe, or 85+20−17 km s−1 Mpc−1 for a flat model with ΩΛ= 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.