COSMIC MICROWAVE BACKGROUND ANISOTROPY INDUCED BY GAS IN CLUSTERS OF GALAXIES

The spectral change induced by Compton scattering of the cosmic microw ave background radiation off hot electron gas in clusters of galaxies is an important component of the anisotropy on arcminute scales. The l evel and spatial characteristics of this anisotropy are explored in de tail in the context of flat cold (taking 0.8 and 1 for the index of th e density fluctuation power spectrum) and mixed dark matter models. Pr operties of intracluster gas and its evolution are directly modeled ba sed on X-ray measurements, with an implied decrease in the gas mass fr action with increasing redshift. Our calculations yield levels of rms temperature anisotropy, (DELTAT/T)rms, almost-equal-to a few 10(-6) fo r a wide range of angular scales and in the context of realistic model s for the intracluster gas evolution and spatial distribution. This is the minimum level of anisotropy expected on subdegree angular scales if the universe underwent a phase of late reheating.