Observational Searches for Galaxies at z > 6

TL;DR

This review summarizes recent observational efforts to detect and analyze galaxies at redshifts greater than six, highlighting techniques, findings, and future prospects for understanding early galaxy formation and cosmic reionization.

Contribution

It provides a comprehensive overview of methods, discoveries, and insights into galaxy evolution at z > 6, emphasizing recent advancements and future observational opportunities.

Findings

Large samples of high-redshift galaxies have been identified.

Spectroscopic confirmation of galaxies up to z ≈ 9.

Insights into galaxy formation and cosmic reionization processes.

Abstract

Although the universe at redshifts greater than six represents only the first one billion years (<10%) of cosmic time, the dense nature of the early universe led to vigorous galaxy formation and evolution activity which we are only now starting to piece together. Technological improvements have, over only the past decade, allowed large samples of galaxies at such high redshifts to be collected, providing a glimpse into the epoch of formation of the first stars and galaxies. A wide variety of observational techniques have led to the discovery of thousands of galaxy candidates at z > 6, with spectroscopically confirmed galaxies out to nearly z = 9. Using these large samples, we have begun to gain a physical insight into the processes inherent in galaxy evolution at early times. In this review, I will discuss i) the selection techniques for finding distant galaxies, including a summary of previous and ongoing ground and space-based searches, and spectroscopic followup efforts, ii) insights into galaxy evolution gleaned from measures such as the rest-frame ultraviolet luminosity function, the stellar mass function, and galaxy star-formation rates, and iii) the effect of galaxies on their surrounding environment, including the chemical enrichment of the universe, and the reionization of the intergalactic medium. Finally, I conclude with prospects for future observational study of the distant universe, using a bevy of new state-of-the-art facilities coming online over the next decade and beyond.