MEASUREMENT OF THE SUNYAEV-ZELDOVICH EFFECT TOWARD ABELL-2163 AT A WAVELENGTH OF 2.2 MILLIMETERS

We report the first significant detection of the Sunyaev-Zel'dovich (S -Z) effect at millimeter wavelengths. Drift scans of the cluster of ga laxies Abell 2163 were performed using a novel bolometric array receiv er at a wavelength of 2.2 millimeters. The measured decrement in sky b rightness corresponds to a peak Comptonization of the cosmic microwave background radiation at the cluster of center y = (3.78(0.74/-0.65)) x 10(-4). Measurements at millimeter wavelengths are necessary to sepa rate the thermal and kinetic S-Z effects. The value of the Hubble cons tant can be derived from the amplitude of the thermal effect in combin ation with the measured X-ray properties of the cluster. The radial pe culiar velocity of the cluster relative to its local CMB rest frame ca n be derived from the relative amplitude of the kinetic and thermal ef fects and the X-ray temperature.