ASCAObservation of the Distant Cluster of Galaxies Cl 0016+16 and Implication forH0

We report the 0.5-10 keV X-ray image and spectrum of Cl 0016+16, which, at a redshift of 0.541, is one of the most distant clusters of galaxies observed with ASCA . The ASCA X-ray image is well represented by an isothermal β model. The best-fit parameters for the core radius (θ c ) and β are 0 6 and 0.7, respectively. However, because of ASCA 's moderate spatial resolution, these two parameters are strongly correlated. The observed spectrum within a 6' radius is well fitted by a thin thermal emission model with a plasma temperature of 8.0 ± 1.0 keV. The Sunyaev-Zeldovich (SZ) effect in Cl 0016+16 has been observed by Carlstrom et al. using an interferometer and by Birkinshaw et al. using a single-dish radio telescope. Combining the SZ microwave decrement with the plasma density and temperature profiles derived from our X-ray observation, we obtained a value of the Hubble constant of 47 ± 14 km s -1 Mpc -1 with the profile parameters obtained by interferometric data, and 52 ± 20 km s -1 Mpc -1 with our best-fit shape parameters and single-dish telescope data.