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

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.