Observations of the Sunyaev-Zel'dovich effect at millimeter wavelengths from the caltech submillimeter observatory

The Sunyaev-Zel'dovich (SZ) effect - the inverse-Compton scattering of Cosmic Microwave Background (CMB) photons by the hot gas in the potential well of galaxy clusters - is a powerful cosmological probe. The thermal and bulk velocities of the electrons in the plasma produce two distinct spectral distortions to the CMB that can be separated from one another by multi-frequency observations spanning 100-400 GHz. Separation of the two components allows the direct determination of the peculiar velocity of the cluster relative to the CMB rest frame. The invariance of the surface brightness of the SZ effect with redshift allows this technique to be extended to redshifts limited only by the existence of rich clusters. In addition, measurements of the thermal component, combined with measurements of the X-ray surface brightness of the cluster, yield a value for the Hubble constant, H ₀. SuZIE, the Sunyaev-Zel'dovich Infrared Experiment, is a bolometric array receiver in use at the Caltech Submillimeter Observatory, that makes observations at 143, 217 and 269 GHz. This instrument is specifically designed to measure both components of the SZ effect at millimeter wavelengths with high precision in galaxy clusters at z > 0.1, and thus to determine cluster peculiar velocities Instruments such as SuZIE will provide important follow-up measurements to the all-sky survey of SZ clusters that will be obtained by the Planck Surveyor satellite and will complement the higher frequency maps of individual clusters that will be available from FIRST.