Astro2020 Science White Paper: Insights Into the Epoch of Reionization with the Highly-Redshifted 21-cm Line

TL;DR

This white paper discusses how the 21-cm line of neutral hydrogen serves as a vital probe for understanding the epoch of reionization, emphasizing the need for advanced analysis techniques and models to interpret upcoming measurements.

Contribution

It highlights the importance of improved 21-cm analysis methods and theoretical models for imaging and understanding the reionization era.

Findings

Upcoming experiments will provide precise statistical measurements.

Enhanced analysis techniques can enable imaging of neutral hydrogen.

Improved models are essential for interpreting reionization data.

Abstract

The epoch of reionization, when photons from early galaxies ionized the intergalactic medium about a billion years after the Big Bang, is the last major phase transition in the Universe's history. Measuring the characteristics of the transition is important for understanding early galaxies and the cosmic web and for modeling dwarf galaxies in the later Universe. But such measurements require probes of the intergalactic medium itself. Here we describe how the 21-cm line of neutral hydrogen provides a powerful probe of the reionization process and therefore important constraints on both the galaxies and intergalactic absorbers at that time. While existing experiments will make precise statistical measurements over the next decade, we argue that improved 21-cm analysis techniques - allowing imaging of the neutral gas itself - as well as improved theoretical models, are crucial for testing our understanding of this important era.