The Role of Dark Matter in Structure Formation during the Epoch of Reionization

Abstract

The Epoch of Reionization represents a pivotal phase in cosmic evolution, during which the first luminous structures ionized the intergalactic medium. While dark matter is established as governing the gravitational collapse that exerts a determinative influence on cosmic structure formation, the precise impact of its particle nature on the morphology and progression of the Epoch of Reionization remains incompletely understood. This investigation examines the role of dark matter during this epoch through comparative analysis of different dark matter scenarios. This study synthesizes results from complementary simulation methodologies—including N-body simulations, hydrodynamical simulations, and semi-numerical techniques—to generate predictive signatures for the evolution of both the 21-cm power spectrum and the galaxy luminosity function during the Epoch of Reionization. Results synthesized from multiple simulation methodologies demonstrate that the Cold Dark Matter framework, with its abundant population of low-mass halos, readily produces rapid reionization consistent with the optical depth measurements from Planck. In contrast, both Warm and Fuzzy Dark Matter models, which suppress small-scale halo formation, predict a characteristically delayed and inhomogeneous reionization process that shows poorer agreement with existing observational constraints.