Measuring the X-ray Background in the Reionization Era with First Generation 21 cm Experiments

TL;DR

This paper proposes using first-generation 21 cm experiments to constrain the poorly known X-ray background during reionization, demonstrating detectability and parameter degeneracy breaking.

Contribution

It introduces a method to calibrate the X-ray background using 21 cm power spectrum measurements from first-generation experiments.

Findings

21 cm signal detectable in redshift 8-14 range

No degeneracy between X-ray and Lyman-Alpha efficiencies

Degeneracy with ionization fraction can be broken

Abstract

The X-ray background during the epoch of reionization is currently poorly constrained. We demonstrate that it is possible to use first generation 21 cm experiments to calibrate it. Using the semi-numerical simulation, 21cmFAST, we calculate the dependence of the 21 cm power spectrum on the X-ray background flux. Comparing the signal to the sensitivity of the Murchison Widefield Array (MWA) we find that in the redshift interval z=8-14 the 21 cm signal is detectable based on the upper limit set by the present-day unresolved soft X-ray background. We show that there is no degeneracy between the X-ray production efficiency and the Lyman-Alpha production efficiency and that the degeneracy with the ionization fraction of the intergalactic medium can be broken.