A Portrait of the Cosmic Reionization History in the Context of the Early Dark Energy Model

Abstract Recent JWST observations of Ly α emission at z ∼ 11–6 indicate a rapid reionization of the intergalactic medium within the first ∼700 Myr. The required Lyman continuum (LyC) photon budget may naturally arise from the unexpectedly high galaxy number densities revealed by JWST, reducing the need for scenarios invoking very high LyC escape fractions ( f esc ≳ 0.2) or dominant contributions from ultrafaint galaxies ( M UV > −15) in the standard ΛCDM framework. In this work, we model the reionization history under the early dark energy (EDE) paradigm—originally proposed to ease the Hubble tension—which also explains the observed overabundance of high- z galaxies without extreme star formation efficiencies. The EDE model yields reionization histories consistent with current constraints while requiring only moderate LyC escape fractions and UV luminosity densities ( f esc ∼ 0.05–0.1, M UV ≲ −17 to −15). Our results suggest that, once key astrophysical parameters are better constrained, the reionization history could serve as an independent and complementary probe of EDE cosmologies.