2006ApJ...647...25B

We determine the distance to 38 clusters of galaxies in the redshift range 0.14≤z≤0.89 using X-ray data from Chandra and Sunyaev-Zeldovich effect (SZE) data from the Owens Valley Radio Observatory and the Berkeley-Illinois-Maryland Association interferometric arrays. The cluster plasma and dark matter distributions are analyzed using a hydrostatic equilibrium model that accounts for radial variations in density, temperature, and abundance, and the statistical and systematic errors of this method are quantified. The analysis is performed via a Markov chain Monte Carlo technique that provides simultaneous estimation of all model parameters. We measure a Hubble constant of H₀=76.9^+3.9_–3.4^+10.0_–8.0 km/s/Mpc (statistical followed by systematic uncertainty at 68% confidence) for an Ω_M=0.3, Ω_Λ=0.7 cosmology. We also analyze the data using an isothermal β-model that does not invoke the hydrostatic equilibrium assumption and find H₀=73.7^+4.6_–3.8^+9.5_–7.6km/s/Mpc; to avoid effects from cool cores in clusters, we repeated this analysis excluding the central 100 kpc from the X-ray data and find H₀=77.6^+4.8_–4.3^+10.1_–8.2 km/s/Mpc (statistical followed by systematic uncertainty at 68% confidence). The consistency between the models illustrates the relative insensitivity of SZE/X-ray determinations of H₀ to the details of the cluster model. Our determination of the Hubble parameter in the distant universe agrees with the recent measurement from the Hubble Space Telescope Key Project that probes the nearby universe.