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 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 H 0 = 76.9 ± 3.93.4 ± 10.0 8.0 km s −1 Mpc −1 (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 H 0 = 73.7 ± 4.63.8 ± 9.5 7.6 km s −1 Mpc −1 ; 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 = 77.6 ± 4.8 4.3 ± 10.1 8.2 km s −1 Mpc −1 (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 -2cluster 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.Subject headings: cosmology: cosmic microwave background; cosmology: distance scale; X-rays: galaxies: clusters SZE/X-ray distances provide a measure of the Hubble constant that is independent of the extragalactic distance ladder and probe high redshifts, well into the Hubble flow. The 1 The clusters with t cool ≤ 0.5t Hubble are 2261. The Hubble time is approximately t Hubble ≃ H −1 0 (Carroll, Press and Turner 1992) with H 0 =72 km s −1 Mpc −1 and the cooling time (t cool ≃ 3k B T /2Λ ee n e ) is calculated using the central density and the temperature from an isothermal β model fit.

We present gas mass fractions of 38 massive galaxy clusters spanning redshifts from 0.14 to 0.89, derived from Chandra X-ray data and OVRO/BIMA interferometric Sunyaev-Zel'dovich Effect (SZE) measurements. We use three models for the gas distribution: (1) an isothermal β-model fit jointly to the X-ray data at radii beyond 100 kpc and to all of the SZE data, (2) a nonisothermal double β-model fit jointly to all of the X-ray and SZE data, and (3) an isothermal β-model fit only to the SZE spatial data. We show that the simple isothermal model well characterizes the intracluster medium (ICM) outside of the cluster core, and provides consistently good fits to clusters spanning a wide range of morphological properties. The X-ray and SZE determinations of mean gas mass fractions for the 100 kpc-cut isothermal β-model are f gas (Xray)= 0.110 +0.003 −0.003 +0.006 −0.018 and f gas (SZE)= 0.116 +0.005 −0.005 +0.009 −0.026 , where uncertainties are statistical followed by systematic at 68% confidence. For the non-isothermal double β-model, f gas (X-ray)= 0.119 +0.003 −0.003 +0.007 −0.014 and f gas (SZE)= 0.121 +0.005 −0.005 +0.009 −0.016 . For the SZE-only model, f gas (SZE)= 0.120 +0.009 −0.009 +0.009−0.027 . The agreement in the results shows that the core can be satisfactorily accounted for by either excluding the core in fits to the X-ray data (the 100 kpc-cut model) or modeling the intracluster gas with a non-isothermal double-β model. We find that the SZE is largely insensitive to structure in the core. Our results indicate that the ratio of the gas mass fraction within r 2500 to the cosmic baryon fraction, f gas Ω B /Ω M , is 0.68 +0.10 −0.16 where the range includes statistical and systematic uncertainties at 68% confidence.-2 -Finally, by assuming that cluster gas mass fractions are independent of redshift, we find that the results are in agreement with standard ΛCDM cosmology and are inconsistent with a flat matter dominated (Ω M = 1) universe.In some clusters the isothermal β model fails to provide a good description of the Xray surface brightness observed in the cluster core. This is the case, for instance, in highly relaxed clusters with sharply peaked central X-ray emission. We have therefore developed two extensions of the isothermal β-model to overcome this limitation; we describe these new models and their application to the X-ray and SZE data below.

The South Pole Telescope (SPT) is currently surveying 2500 deg 2 of the southern sky to detect massive galaxy clusters out to the epoch of their formation using the Sunyaev-Zel'dovich (SZ) effect. This paper presents a catalog of the 26 most significant SZ cluster detections in the full survey region. The catalog includes 14 clusters which have been previously identified and 12 that are new discoveries. These clusters were identified in fields observed to two differing noise depths: 1500 deg 2 at the final SPT survey depth of 18 μK arcmin at 150 GHz and 1000 deg 2 at a depth of 54 μK arcmin. Clusters were selected on the basis of their SZ signal-to-noise ratio (S/N) in SPT maps, a quantity which has been demonstrated to correlate tightly with cluster mass. The S/N thresholds were chosen to achieve a comparable mass selection across survey fields of both depths. Cluster redshifts were obtained with optical and infrared imaging and spectroscopy from a variety of ground-and space-based facilities. The redshifts range from 0.098 z 1.132 with a median of z med = 0.40. The measured SZ S/N and redshifts lead to unbiased mass estimates ranging from 9.8 × 10 14 M h −1 70 M 200 (ρ mean) 3.1 × 10 15 M h −1 70. Based on the SZ mass estimates, we find that none of the clusters are individually in significant tension with the ΛCDM cosmological model. We also test for evidence of non-Gaussianity based on the cluster sample and find the data show no preference for non-Gaussian perturbations.

We present Sunyaev-Zel'dovich Effect (SZE) scaling relations for 38 massive galaxy clusters at redshifts 0.14 ≤ z ≤ 0.89, observed with both the Chandra X-ray Observatory and the centimeter-wave SZE imaging system at the BIMA and OVRO interferometric arrays. An isothermal β-model with central 100 kpc excluded from the X-ray data is used to model the intracluster medium and to measure global cluster properties. For each cluster, we measure the X-ray spectroscopic temperature, SZE gas mass, total mass and integrated Compton-y parameters within r 2500 . Our measurements are in agreement with the expectations based on a simple self-similar model of cluster formation and evolution. We compare the cluster properties derived from our SZE observations with and without Chandra spatial and spectral information and find them to be in good agreement. We compare our results with cosmological numerical simulations, and find that simulations that include radiative cooling, star formation and feedback match well both the slope and normalization of our SZE scaling relations.