Sunyaev‐Zeldovich Effect–derived Distances to the High‐Redshift Clusters MS 0451.6−0305 and Cl 0016+16

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-Zeldovich 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 km s -1 Mpc -1 , where the uncertainties correspond to statistical followed by systematic at 68% confidence. The best-fit H 0 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.