COMPTONIZATION OF THE COSMIC MICROWAVE BACKGROUND BY GAS IN SUPERCLUSTERS OF GALAXIES

Our systematic X-ray searches in the HEAO 1 A-2 database have yielded- for the first time-a direct bound on the properties of hot gas in supe rclusters (SCs) of galaxies. The bound translates to a mean Comptoniza tion parameter whose value is lower than a few x 10(-7) in a SC. The i mplied anisotropy in the spatial distribution of the cosmic microwave background (CMB) radiation due to gas in SCs is DELTAT/T less-than-or- equal-to 10(-7) on a characteristic angular scale of a few degrees. CM B Comptonization by gas in SCs is an unlikely source of the anisotropy on scales of approximately 10-degrees detected by COBE.