REIONIZATION AND THE COSMIC MICROWAVE BACKGROUND IN AN OPEN UNIVERSE

If the universe was reionized at high redshift (z greater-than-or-similar-to 30) or never recombined, then photon-electron scattering can erase fluctuations in the cosmic microwave background at scales greater-than-or-similar-to 1-degree. Peculiar motion at the surface of last scattering will then have given rise to new anisotropy at the 1' level through the Vishniac effect. Here the observed fluctuations in galaxy counts are extrapolated to high redshifts using linear theory, and the expected anisotropy is computed. The predicted level of anisotropies is a function of OMEGA0 and the ratio of the density in ionized baryons to the critical density and is shown to depend strongly on the large- and small-scale power. It is not possible to make general statements about the viability of all reionized models based on current observations, but it is possible to rule our specific models for structure formation, particularly those with high baryonic content or small-scale power. The induced fluctuations are shown to scale with cosmological parameters and optical depth.