COSMIC MICROWAVE BACKGROUND ANISOTROPY INDUCED BY GAS IN CLUSTERS OF GALAXIES

The spectral change induced by Compton scattering of the cosmic microwave background radiation off hot electron gas in clusters of galaxies is an important component of the anisotropy on arcminute scales. The level and spatial characteristics of this anisotropy are explored in detail in the context of flat cold (taking 0.8 and 1 for the index of the density fluctuation power spectrum) and mixed dark matter models. Properties of intracluster gas and its evolution are directly modeled based on X-ray measurements, with an implied decrease in the gas mass fraction with increasing redshift. Our calculations yield levels of rms temperature anisotropy, (DELTAT/T)rms, almost-equal-to a few 10(-6) for a wide range of angular scales and in the context of realistic models 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.