Probing galaxy evolution through HI 21-cm emission and absorption: current status and prospects with the Square Kilometre Array

TL;DR

This paper reviews current knowledge of atomic hydrogen (HI) in galaxy evolution through 21-cm line observations and discusses future prospects with the Square Kilometre Array (SKA) and its precursors.

Contribution

It provides a comprehensive overview of HI 21-cm emission and absorption studies and outlines the potential scientific advancements with SKA in understanding galaxy evolution.

Findings

Current understanding of HI gas in galaxies

Potential of SKA for high-redshift HI studies

Future capabilities of SKA and precursors

Abstract

One of the major science goals of the Square Kilometre Array (SKA) is to understand the role played by atomic hydrogen (HI) gas in the evolution of galaxies throughout cosmic time. The hyperfine transition line of the hydrogen atom at 21-cm is one of the best tools to detect and study the properties of HI gas associated with galaxies. In this article, we review our current understanding of HI gas and its relationship with galaxies through observations of the 21-cm line both in emission and absorption. In addition, we provide an overview of the HI science that will be possible with SKA and its pre-cursors and pathfinders, i.e. HI 21-cm emission and absorption studies of galaxies from nearby to high redshifts that will trace various processes governing galaxy evolution.