Warm Dark Matter and Cosmic Reionization

TL;DR

This paper investigates how warm dark matter with keV-scale particles affects cosmic reionization, using galaxy luminosity functions and Gunn-Peterson observations to constrain models and highlight the model dependence of dark matter inferences.

Contribution

It provides new constraints on warm dark matter models near 3 keV by analyzing reionization signatures and emphasizes the importance of star formation modeling.

Findings

Delayed reionization signature in WDM models.

Reionization observables are sensitive to star formation and feedback models.

Current data cannot definitively distinguish dark matter types due to model uncertainties.

Abstract

In models with dark matter made of particles with keV masses, such as a sterile neutrino, small-scale density perturbations are suppressed, delaying the period at which the lowest mass galaxies are formed and therefore shifting the reionization processes to later epochs. In this study, focusing on Warm Dark Matter (WDM) with masses close to its present lower bound, i.e. around the $3$ keV region, we derive constraints from galaxy luminosy functions, the ionization history and the Gunn-Peterson effect. We show that even if star formation efficiency in the simulations is adjusted to match the observed UV galaxy luminosity functions in both CDM and WDM models, the full distribution of Gunn-Peterson optical depth retains the strong signature of delayed reionization in the WDM model. However, until the star formation and stellar feedback model used in modern galaxy formation simulations is constrained better, any conclusions on the nature of dark matter derived from reionization observables remain model-dependent.