Measurement of the cosmic distance scale from Chandra X-ray imaging and Sunyaev-Zel'dovich Effect mapping of high redshift clusters of galaxies
Abstract
Galaxy clusters are the most massive gravitational structures in the universe, and also provide unique probes of its expansion. Their strong X-ray emission and unique cosmic microwave background scattering signature afford an independent method to obtain distances based on the physics of ionized plasmas. In this article we determine the distance to 39 clusters of galaxies in the redshift range 0.14<z<0.89 using Chandra X-ray data and radio observations from the OVRO and BIMA interferometric arrays. We analyze the plasma and dark matter distribution in clusters using a hydrostatic equilibrium model that accounts for radial variations in density, temperature and abundance, and quantify the statistical and systematic errors of this method. 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 H_0= 77.1 +3.8-3.4 +10.0-8.0 Km/s/Mpc (statistical followed by systematic uncertainty at 68% confidence) for an Omega_M=0.3, Omega_Lambda=0.7 cosmology. We also analyze the data using an isothermal beta model that is free of the hydrostatic equilibrium assumption, and find H_0=73.4 +4.5-3.8 +9.5-7.6 Km/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 H_0= 77.2 +4.8-4.2 +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 H_0 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.Keywords
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