Impact of inhomogeneous reionization on cosmic microwave background anisotropy

It is likely that the reionization of the Universe did not occur homogeneously. Using a model that associates ionized patches with overdense regions, we find that the resulting cosmic microwave background (CMB) anisotropy power spectrum peaks at angular scales corresponding to the extent of the ionized regions, and has a width that reflects the correlations between them. There is considerable uncertainty in the amplitude. Neglecting inhomogeneous reionization in the determination of cosmological parameters from high resolution CMB maps may cause significant systematic error.