Imprint of Inhomogeneous Reionization on the Power Spectrum of Galaxy Surveys at High Redshifts

Abstract

We consider the effects of inhomogeneous reionization on the distribution of galaxies at high redshifts. Modulation of the formation process of the ionizing sources by large-scale density modes makes reionization inhomogeneous and introduces a spread to the reionization times of different regions with the same size. After sources photoionize and heat these regions to a temperature ≳104 K at different times, their temperatures evolve as the ionized intergalactic medium (IGM) expands. The varying IGM temperature makes the minimum mass of galaxies spatially nonuniform with a fluctuation amplitude that increases toward small scales. These scale-dependent fluctuations modify the shape of the power spectrum of low-mass galaxies at high redshifts in a way that depends on the history of reionization. The resulting distortion of the primordial power spectrum is significantly larger than changes associated with uncertainties in the inflationary parameters, such as the spectral index of the scalar power spectrum or the running of the spectral index. Future surveys of high-redshift galaxies will offer a new probe of the thermal history of the IGM but might have a more limited scope in constraining inflation.