We determine the distances to 18 galaxy clusters with redshifts ranging from z ∼ 0.14 to z ∼ 0.78 from a maximum likelihood joint analysis of 30 GHz interferometric Sunyaev-Zel'dovich effect (SZE) and X-ray observations. We model the intracluster medium (ICM) using a spherical isothermal β model. We quantify the statistical and systematic uncertainties inherent to these direct distance measurements, and we determine constraints on the Hubble parameter for three different cosmologies. These distances imply a Hubble constant of 60 +4 −4 +13 −18 km s −1 Mpc −1 for an Ω M = 0.3, Ω Λ = 0.7 cosmology, where the uncertainties correspond to statistical followed by systematic at 68% confidence. With a sample of 18 clusters, systematic uncertainties clearly dominate. The systematics are observationally approachable and will be addressed in the coming years through the current generation of X-ray satellites (Chandra & XMM-Newton) and radio observatories (OVRO, BIMA, & VLA). Analysis of high redshift clusters detected in future SZE and X-ray surveys will allow a determination of the geometry of the universe from SZE determined distances.

We derive correlations between X-ray temperature, luminosity, and gas mass for a sample of 22 distant, z > 0.4, galaxy clusters observed with Chandra. We detect evolution in all three correlations between z > 0.4 and the present epoch. In particular, in the Ω = 0.3, Λ = 0.7 cosmology, the luminosity corresponding to a fixed temperature scales approximately as (1 + z) 1.5±0.3 ; the gas mass for a fixed luminosity scales as (1 + z) −1.8±0.4 ; and the gas mass for a fixed temperature scales as (1 + z) −0.5±0.4 (all uncertainties are 90% confidence). We briefly discuss the implication of these results for cluster evolution models.

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We present serendipitous observations of radio sources at 28.5 GHz (1 cm), which resulted from our program to image thermal Sunyaev-Zeldovich (SZ) effect in 56 galaxy clusters. In a total area of ∼ 0.8 • sq., we find 64 radio sources with fluxes down to ∼ 0.4 mJy (> 4σ), and within 250 ′′ from the pointing centers. The spectral indices (S ∝ ν −α ) of 54 sources with published low frequency flux densities range from −0.6 α 2 with a mean of 0.77 ± 0.06, and a median of 0.84. Extending low frequency surveys of radio sources towards galaxy clusters CL 0016+16, Abell 665, and Abell 2218 to 28.5 GHz, and selecting sources with S 1.4GHz ≥ 7 mJy to form an unbiased sample, we find a mean spectral index of 0.71 ± 0.08 and a median of 0.71. We find 4 to 7 times more sources predicted from a low frequency survey in areas without galaxy clusters. This excess cannot be accounted for by gravitational lensing of a background radio population by cluster potentials, indicating most of the detected sources are associated with galaxy clusters. The differential source count slope, γ ∼ 1.96 (dN/dS ∝ S −γ ), is flatter than what is expected for a nonevolving Euclidean population (γ = 2.5). For the cluster Abell 2218, the presence of unsubtracted radio sources with S 28.5GHz ≤ 0.5 mJy (∼ 5 σ), can only contribute to temperature fluctuations at a level of ∆T ∼ 10 to 25 µK. The corresponding error due to radio point source contamination in the Hubble constant derived through a combined analysis of 28.5 GHz SZ images and X-ray emission observations ranges from 1% to 6%.

We determine the distances to the z 0.55 galaxy clusters MS 0451.6 − 0305 and CL 0016 + 16 from a maximum likelihood joint fit to interferometric Sunyaev-Zel'dovich effect (SZE) and X-ray observations. We model the intracluster medium (ICM) using a spherical isothermal β-model. We quantify the statistical and systematic uncertainties inherent to these direct distance measurements, and we determine constraints on the Hubble parameter for three different cosmologies. For an Ω M = 0.3, Ω Λ = 0.7 cosmology, these distances imply a Hubble constant of 63 +12 − 9 +21 −21 km s −1 Mpc −1 , where the uncertainties correspond to statistical followed by systematic at 68% confidence. The best fit H • is 57 km s −1 Mpc −1 for an open Ω M = 0.3 universe and 52 km s −1 Mpc −1 for a flat Ω M = 1 universe. Subject headings: cosmic microwave background-cosmology: observations-distance scalegalaxies: clusters: individual (MS 0451.6 − 0305; CL 0016 + 16)-techniques: interferometric