Prospects of fast radio bursts and large-scale 21 cm power spectra in constraining the Epoch of Reionization

The Epoch of Reionization (EoR) is a crucial link through which the complete evolutionary history of the Universe can be grasped. Several attempts with a variety of observables have been used to understand the thermal and ionization evolution of the intergalactic medium during EoR. In this study, we explore the simultaneous prospects of two important observables that are expected to be available in the near future, that is, the dispersion measure (DM) of high-redshift fast radio bursts (FRBs) and large-scale 21 cm power spectra. For this purpose, we used a previously developed explicitly photon conserving seminumerical model, SCRIPT, which includes realistic recombination and radiative feedback effects. We verified that the DM evolution of 100 mock FRBs at high redshift (7.0 <= z <= 15.0) is sufficient to recover the underlying reionization model, while 1000 FRB mocks at this redshift range can constrain the reionization timeline within the percentage level uncertainties at the 68% confidence limit. Furthermore, we studied the effect of including large-scale 21 cm power spectra (using only a single bin, k similar to 0.14 h/cMpc) at three redshifts along with the FRB DM distribution. The joint exploration using these two observables can significantly improve the constraints on the various parameters ( an uncertainty of less than or similar to 8% for the reionization interval and midpoint at the 95% confidence), alleviate the degeneracies, and can narrow down the thermal history of the Universe by discarding some of the extreme heating models.