Galaxies and Black Holes in the First Billion Years

TL;DR

This paper summarizes recent observational progress using JWST in understanding early galaxies and black holes within the first billion years, focusing on cosmic reionisation, galaxy properties, and Population III stars.

Contribution

It provides an overview of JWST findings on high-redshift galaxies and black holes, emphasizing observational results, methods, and future goals in early universe studies.

Findings

Advances in observing galaxies during reionisation era

Detection of early black hole activity

Insights into Population III star candidates

Abstract

I present written notes from three lectures given at the 54th Saas-Fee Advanced Course of the Swiss Society of Astrophysics and Astronomy in January 2025 entitled "Galaxies and Black Holes in the First Billion Years as seen by the JWST". I focused my lectures on progress in studies of cosmic reionisation, the properties of galaxies in the reionisation era, topics related to the redshift frontier and the search for Population III stars. The lectures were given to graduate students in astrophysics and cover both pedagogical material as well as observational results from the first two and half years of JWST science operations. The pace of discovery with JWST is, of course, rapid and so my lectures discuss long-term goals, analysis methods and their assumptions and limitations in the hope that the underlying material will retain value in the near future. In this written version, the visual material is that presented at Saas-Fee in January 2025 but I have provided updates on progress from the literature up to August 2025. The material is aimed at early career researchers and should not be considered as a scholarly review of the entire JWST literature on high redshift galaxies