Predictions for the 21cm-galaxy cross-power spectrum observable with LOFAR and Subaru

TL;DR

This paper assesses the potential to observe the 21cm-galaxy cross-power spectrum during the Epoch of Reionization using LOFAR and Subaru, predicting detectable anti-correlations on large scales through simulations.

Contribution

It provides the first detailed simulation-based predictions of the 21cm-galaxy cross-power spectrum for LOFAR and Subaru observations during the EoR, including noise and projection effects.

Findings

Detectable anti-correlation on scales > 60 h$^{-1}$ Mpc with significance p≈0.04-0.048.

Predicted contamination of the signal on smaller scales.

Simulation results guide observational strategies for EoR studies.

Abstract

The 21cm-galaxy cross-power spectrum is expected to be one of the promising probes of the Epoch of Reionization (EoR), as it could offer information about the progress of reionization and the typical scale of ionized regions at different redshifts. With upcoming observations of 21cm emission from the EoR with the Low Frequency Array (LOFAR), and of high redshift Lyalpha emitters (LAEs) with Subaru's Hyper Suprime Cam (HSC), we investigate the observability of such cross-power spectrum with these two instruments, which are both planning to observe the ELAIS-N1 field at z=6.6. In this paper we use N-body + radiative transfer (both for continuum and Lyalpha photons) simulations at redshift 6.68, 7.06 and 7.3 to compute the 3D theoretical 21cm-galaxy cross-power spectrum, as well as to predict the 2D 21cm-galaxy cross-power spectrum expected to be observed by LOFAR and HSC. Once noise and projection effects are accounted for, our predictions of the 21cm-galaxy cross-power spectrum show clear anti-correlation on scales larger than ~ 60 h$^{-1}$ Mpc (corresponding to k ~ 0.1 h Mpc$^{-1}$), with levels of significance p=0.04 at z=6.6 and p=0.048 at z=7.3. On smaller scales, instead, the signal is completely contaminated.