Abstract
Abstract
We present a study of the transition of neutral hydrogen (HI) gas from the end of the Epoch of Reionization (EoR) to late-time large-scale structure. We examine the signature of the transition as traced through the redshifted 21-cm line with SKA-Low at 3 < z < 7. To do so, we use the semi-numerical simulation 21cmFAST to model the HI during the EoR, adding a HI-halo based post-processing model of the late-time HI. This approach gives a robust estimate of the amplitude of the HI temperature field and predicts the observable power spectrum during the transition period. We find that our simulation pipeline reproduces the expected power spectrum trends from existing observations and theory, in addition to replicating observational constraints on ΩHI. Our simulations predict a drop in power of four orders of magnitude between 4 < z < 7. Assuming an inhomogeneous recombination model, we find a flattening of the power, due to lingering neutral islands masking the late-time HI signal, for 5 < z < 6.5. Using SKA-Low deep survey parameters, we find HI power spectrum detectability at scales k ≤ 1hMpc−1 across redshifts 3 < z < 7, even when using the horizon limit to mitigate foregrounds. Our results suggest that the resulting ΩHI constraints can trace different reionization scenarios such as a decreased escape fraction. This study implies that deep SKA-Low observations post-reionization will be an important probe to constrain reionization parameters as well as cosmological models.