THE SUNYAEV-ZELDOVICH INFRARED EXPERIMENT - A MILLIMETER-WAVE RECEIVER FOR CLUSTER COSMOLOGY

Measurements of the Sunyaev-Zeldovich (S-Z) effect toward distant clus ters of galaxies can be used to the Hubble constant and the radial com ponent of cluster peculiar velocities. Determination of the cluster pe culiar velocity requires the separation of the two components of the S -Z effect, which are due to the thermal and bulk velocities of the int racluster plasma. The two components can be separated practically only at millimeter wavelengths. Measurements of the S-Z effect at millimet er wavelengths are subject to minimal astrophysical confusion and, the refore, provide an important test of results obtained at longer wavele ngths. We describe the instrument used to make the first significant d etections of the S-Z effect at millimeter wavelengths. This instrument employs new filter, detector, and readout technologies to produce sen sitive measurements of differential sky brightness stable on long time scales. These advances allow drift-scan observations that achieve high sensitivity while minimizing common sources of systematic error.