New simulation of QSO X-ray heating during the Cosmic Dawn

TL;DR

This paper presents advanced simulations of X-ray heating during the Cosmic Dawn, highlighting the impact of QSO-like sources on the 21-cm signal and its non-Gaussian features, which are detectable by upcoming radio telescopes.

Contribution

It introduces the first large-volume simulations including QSO-like sources, demonstrating their significant effect on the 21-cm signal's non-Gaussianity during the Cosmic Dawn.

Findings

QSO-like sources increase non-Gaussianity of the 21-cm signal.

Simulated images are distinguishable at SKA1-LOW resolution.

Inclusion of QSOs results in RMS fluctuations above expected noise.

Abstract

The upcoming radio interferometer Square Kilometre Array is expected to directly detect the redshifted 21-cm signal from the Cosmic Dawn for the first time. In this era temperature fluctuations from X-ray heating of the neutral intergalactic medium can impact this signal dramatically. Previously, in (Ross et al, 2017), we presented the first large-volume, 244 $h^{-1}$Mpc = 349 Mpc a side, fully numerical radiative transfer simulations of X-ray heating. This work is a follow-up where we now also consider QSO-like sources in addition to high mass X-ray binaries. Images of the two cases are clearly distinguishable at SKA1-LOW resolution and have RMS fluctuations above the expected noise. The inclusion of QSOs leads to a dramatic increase in non-Gaussianity of the signal, as measured by the skewness and kurtosis of the 21-cm signal. We conclude that this increased non-Gaussianity is a promising signature of early QSOs.