ABSTRACT 9503226 LANGE, Andrew E. The Cosmic Microwave Background (CMB) radiation provides an extremely uniform back light to the observable universe. Through photon-electron (Compton) scattering of the CMB photons with the hot, ionized plasma that is gravitationally bound in clusters of galaxies a distortion known as the Sunyaev-Zel'dovich (SZ) effect alters the spectrum of the CMB when viewed through a cluster. The thermal and bulk velocities of the electrons in the intra-cluster medium produce distinct spectral distortions that can be distinguished from one another by multifrequency observations in the 100 to 300 GHz range. Separation of these two components allows the direct determination of the peculiar velocity of the cluster relative to the quasi-inertial CMB rest frame. The invariance of the surface brightness of the SZ effect with red shift allows this technique to be extended to red shifts limited only by the existence of rich clusters. Also, measurements of the thermal component of the intra-cluster medium combined with measurements of the X-ray surface brightness of the cluster yields a value of the very fundamental Hubble constant, Ho. The PI will construct a new, multi-frequency array (SuZIE II) which employs frequency correlation and an increased number of pixels to greatly increase the sensitivity of observations to the SZ effect and to CMB anisotropy on arcminute scales. SuZIE II will measure the peculiar velocity field of many high red shift clusters, measure the arcminute scale anisotropy of the CMB with high precision, and determine a value for Ho based on a large and carefully selected sample of clusters. ***
