Quasars as probes of cosmological reionization

TL;DR

This review discusses how high-redshift quasars serve as powerful tools to study the epoch of reionization, detailing observational techniques, absorption phenomena, and future research directions.

Contribution

It provides a comprehensive overview of methods and findings related to using quasars to probe the reionization history of the universe.

Findings

Identification of high-redshift quasars constrains reionization timeline.

Analysis of absorption features reveals properties of the intergalactic medium.

Future surveys will enhance understanding of reionization through quasar observations.

Abstract

Quasars are the most luminous non-transient sources in the epoch of cosmological reionization (i.e., which ended a billion years after the Big Bang, corresponding to a redshift of z ~ 5), and are powerful probes of the inter-galactic medium at that time. This review covers current efforts to identify high-redshift quasars and how they have been used to constrain the reionization history. This includes a full description of the various processes by which neutral hydrogen atoms can absorb/scatter ultraviolet photons, and which lead to the Gunn-Peterson effect, dark gap and dark pixel analyses, quasar near zones and damping wing absorption. Finally, the future prospects for using quasars as probes of reionization are described.