Constraints on Features in the Cosmological Power Spectrum from Observations of the Epoch of Reionization

Cosmological models with a power spectrum of perturbations featuring an enhanced amplitude on dwarf galaxy scales (with a ‘‘bump’’ or a ‘‘tilt’’) are considered. Early formation of a large number of galaxies in such models, compared to the standard spectrum, can shift the epoch of reionization to higher redshifts compared to observations. It is shown that for moderate bump amplitude A<1.5-2 , the considered models are not ruled out by observations of reionization at z≈ 8 due to existing uncertainties in the fraction of ultraviolet photons escaping galaxies, fesc , and inhomogeneity of the neutral hydrogen distribution.