Galaxy clusters and microwave background anisotropy

Previous estimates of the microwave background anisotropies produced byfreely falling spherical clusters are discussed. These estimates are based onthe Swiss-Cheese and Tolman-Bondi models. It is proved that these models giveonly upper limits to the anisotropies produced by the observed galaxy clusters.By using spherically symmetric codes including pressureless matter and a hotbaryonic gas, new upper limits are obtained. The contributions of the hot gasand the pressureless component to the total anisotropy are compared. Theeffects produced by the pressure are proved to be negligible; hence,estimations of the cluster anisotropies based on N-body simulations arehereafter justified. After the phenomenon of violent relaxation, any realisticrich cluster can only produce small anisotropies with amplitudes of order$10^{-7}$. During the rapid process of violent relaxation, the anisotropiesproduced by nonlinear clusters are expected to range in the interval$(10^{-6},10^{-5})$. The angular scales of these anisotropies are discussed.Comment: 31 pages, 3 postscript figures, accepted MNRA