Measuring the History of Cosmic Reionization using the 21-cm PDF from Simulations

TL;DR

This paper uses simulations to analyze the 21-cm brightness temperature distribution during cosmic reionization, proposing a method to extract the reionization history with high accuracy from upcoming experiments.

Contribution

It introduces an empirical fit to the 21-cm PDF from simulations and assesses the potential of future experiments to measure reionization history.

Findings

Upcoming experiments can measure reionization history to 1-10% accuracy.

A simple empirical fit effectively models the 21-cm PDF during reionization.

Higher noise levels require more flexible models for accurate measurements.

Abstract

The 21-cm PDF (i.e., distribution of pixel brightness temperatures) is expected to be highly non-Gaussian during reionization and to provide important information on the distribution of density and ionization. We measure the 21-cm PDF as a function of redshift in a large simulation of cosmic reionization and propose a simple empirical fit. Guided by the simulated PDF, we then carry out a maximum likelihood analysis of the ability of upcoming experiments to measure the shape of the 21-cm PDF and derive from it the cosmic reionization history. Under the strongest assumptions, we find that upcoming experiments can measure the reionization history in the mid to late stages of reionization to 1-10% accuracy. Under a more flexible approach that allows for four free parameters at each redshift, a similar accuracy requires the lower noise levels of second-generation 21-cm experiments.