Consistently Reproducing Early Galaxy Observations and 21-cm Signal during the Epoch of Reionization
Year: 2026
Type: preprint
Abstract: In the standard cosmological model, galaxies forming within dark matter haloes are the primary drivers of the Epoch of Reionization (EoR). The complex physics of galaxy formation introduces scatter in the relation between halo mass and star-formation activity, with implications for the production and escape of ionising photons. In this work, we implement a stochastic source model in our cosmological radiative transfer simulations. We calibrate our model against the high-redshift ultraviolet luminosity function observed by JWST and observational constraints on Lyman-continuum leakage to constrain the ionising escape fraction. We find that stochastic star formation redistributes ionising emissivity toward lower-mass haloes, producing a more fragmented ionisation topology and delaying the growth of the largest ionised regions relative to the deterministic, observationally calibrated model. However, when the two models match total ionising photon production, their global neutral fractions and 21-cm power spectrum remain nearly indistinguishable, despite small differences in the morphology of individual ionised regions. Additionally, we establish a unified framework that lets us apply source models derived from computationally expensive hydrodynamical simulations (SPICE, FIRE-2 and Thesan) and investigate their impact on large-volume reionisation simulations, extending their prescriptions to scales of >100 Mpc. We find that these prescriptions produce distinct ionisation topologies and 21-cm statistical signatures, even when their global reionisation histories are similar. Our results highlight the importance of combining physically motivated galaxy formation prescriptions from hydrodynamical simulations with large-volume radiative transfer simulations to interpret forthcoming 21-cm observations and constrain the sources of cosmic reionisation.
Source: arXiv (Cornell University)
Institutions: ETH Zurich, Institute for Particle Physics and Astrophysics, Stockholm University, AlbaNova, Centre National de la Recherche Scientifique, Centre de Recherche Astrophysique de Lyon, University of Zurich, Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7222995676