Studying the Sources of Cosmic Reionization with 21-cm Fluctuations

TL;DR

This paper investigates how 21-cm power spectrum measurements during reionization can simultaneously constrain the history of reionization and the properties of ionizing sources, using simulations and analytical modeling.

Contribution

It introduces a flexible six-parameter model and demonstrates that one-year observations can accurately measure ionization fractions and source properties.

Findings

Reionization fraction can be measured to ~1% accuracy at the end of reionization.

Halo mass of ionizing sources can be measured to 10-20% accuracy during reionization.

MWA array observations can effectively constrain reionization and galaxy formation histories.

Abstract

We explore the ability of measurements of the 21-cm power spectrum during reionization to enable the simultaneous reconstruction of the reionization history and the properties of the ionizing sources. For various sets of simulated 21-cm measurements, we perform maximum likelihood fits in order to constrain the reionization and galaxy formation histories. We employ a flexible six-parameter model that parametrizes the uncertainties in the properties of high-redshift galaxies. The computational speed needed is attained through the use of an analytical model that is in reasonable agreement with numerical simulations of reionization. We find that one-year observations with the MWA array should measure the cosmic ionized fraction to ~ 1% accuracy at the very end of reionization, and a few percent accuracy around the mid-point of reionization. The mean halo mass of the ionizing sources should be measureble to 10% accuracy when reionization is 2/3 of the way through, and to 20% accuracy throughout the central stage of reionization, if this mass is anywhere in the range 1/3 to 100 billion solar masses.