POLAR

II. Modeling the star formation history of galaxies on the 21 cm signal from the Epoch of Reionization

¹ School of Physics and Electronic Science, Guizhou Normal University, Guiyang 550001, PR China
² Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing, Guizhou Normal University, Guiyang 550001, PR China
³ Department of Physical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, WB 741 246, India
⁴ Max-Planck Institute für Astrophysics, Karl-Schwarzschild-Straße 1, 85748 Garching bei München, Germany
⁵ Berkeley Center for Cosmological Physics, Department of Physics, University of California, Berkeley, CA 94720, USA
⁶ National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing, 100101, China
⁷ State Key Laboratory of Radio Astronomy and Technology, Beijing 100101, China
⁸ Astronomy Centre, Department of Physics and Astronomy, University of Sussex, Falmer, Brighton BN19QH, UK
⁹ Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, NL-9700AV, Groningen, The Netherlands
¹⁰ The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-10691 Stockholm, Sweden
¹¹ ARCO (Astrophysics Research Center), Department of Natural Sciences, The Open University of Israel, 1 University Road, PO Box 808 Ra’anana, 4353701, Israel

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 20 December 2025
Accepted: 4 March 2026

Abstract

Context. Galaxies may suffer some starburst and quenched periods in their history due to galaxy mergers and feedback. However, semi-numerical simulations of the Epoch of Reionization (EoR) do not accurately model the effects of the star formation history (SFH) of galaxies.

Aims. Keeping the same total ionizing photon budget from galaxies, we investigate how the ionization and heating of the intergalactic medium (IGM), as well as the associated 21 cm signal during the EoR, depend on the variations in modeling the SFH of galaxies.

Methods. We adopted the JIUTIAN-300 N-body dark matter simulation and the semi-analytic model L-GALAXIES 2020 to model galaxy formation. Using the galaxy catalog from L-GALAXIES 2020 as input, we post-processed the JIUTIAN-300 density field with the 1D radiative transfer code GRIZZLY to model the reionization process and the 21 cm signal.

Results. We find that the ionized regions produced by galaxies with a SFH derived from L-GALAXIES 2020 are slightly larger and warmer than the ones obtained with a constant star formation rate. For a fixed stellar mass, galaxies produce smaller ionized regions with increasing stellar-mass-weighted stellar age τ_age. This results in a different topology and timing of the IGM ionization and heating obtained from GRIZZLY.

Conclusions. The SFH of galaxies is highly dependent on τ_age and redshift. Different models of the galactic SFH affect the gas heating and ionizing processes during the EoR and, as a consequence, also affect the 21 cm global signal and power spectrum.