The cross-power spectrum between 21cm emission and galaxies in hierarchical galaxy formation models

TL;DR

This paper models the evolution of the cross-power spectrum between 21cm emission and galaxies during reionization, highlighting how feedback processes influence its shape and amplitude, and assesses its detectability with upcoming surveys.

Contribution

It combines hierarchical galaxy formation models with ionization structure simulations to study the cross-power spectrum's evolution and its sensitivity to feedback processes.

Findings

Feedback processes alter the cross-power spectrum shape and amplitude.

Supernovae feedback significantly impacts the ionized region features.

The cross-power spectrum can be detected with upcoming galaxy surveys and MWA data.

Abstract

The correlation between 21cm fluctuations and galaxies is sensitive to the astrophysical properties of the galaxies that drove reionization. Thus, detailed measurements of the cross-power spectrum and its evolution could provide a powerful measurement both of the properties of early galaxies and the process of reionization. In this paper, we study the evolution of the cross-power spectrum between 21cm emission and galaxies using a model which combines the hierarchical galaxy formation model GALFORM implemented within the Millennium-II dark matter simulation, with a semi-numerical scheme to describe the resulting ionization structure. We find that inclusion of different feedback processes changes the cross-power spectrum shape and amplitude. In particular, the feature in the cross-power spectrum corresponding to the size of ionized regions is significantly affected by supernovae feedback. We calculate predicted observational uncertainties of the cross-correlation coefficient based on specifications of the Murchison Widefield Array (MWA) combined with galaxy surveys of varying area and depth. We find that the cross-power spectrum could be detected over several square degrees of galaxy survey with galaxy redshift errors less than 0.1.