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

TL;DR

This paper investigates how features in the primordial power spectrum, such as bumps or tilts, affect the timing of reionization, and finds that certain models with moderate enhancements remain consistent with current observations.

Contribution

It introduces constraints on features in the cosmological power spectrum based on reionization epoch observations, considering uncertainties in galaxy photon escape fractions.

Findings

Models with moderate bump amplitude are not ruled out by current reionization data.

Enhanced power on dwarf galaxy scales can lead to earlier galaxy formation.

Uncertainties in photon escape fraction affect constraints on power spectrum features.

Abstract

We consider cosmological models with a power spectrum of perturbations featuring an enhanced amplitude on dwarf galaxy scales (with a "bump" or a "tilt"). 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. We show that for moderate bump amplitude $\mathcal{A}<1.5-2$, the considered models are not ruled out by observations of reionization at $z \approx 8$ due to existing uncertainties in the fraction of ultraviolet photons escaping galaxies, $f_{esc}$, and inhomogeneity of the neutral hydrogen distribution.