Witnessing galaxy formation in the most distant galaxy clusters

Galaxy clusters are the densest places a galaxy can live, containing thousands of individual galaxies bound together by their mutual gravitational attraction. Cluster galaxies typically differ in colour and shape from galaxies that reside in the less dense field implying that galaxies are influenced by their environment. Some of these differences are caused by the dense environment acting on the galaxies today, but there are also subtle differences that must have been set long ago. For example, cluster galaxies are typically more massive, older and larger than field galaxies, implying that a galaxy's surroundings during its birth also have an important and lasting influence. Determining the environment of a galaxy in the early Universe is extremely challenging, so we currently know very little about the role of environment during a galaxy's birth. This has resulted in a large gap in our understanding of how the Universe evolved. In this Ph.D. project we will use state-of-the-art observations of the most distant galaxy clusters in the Universe to understand how galaxies are influenced by their surroundings whilst they are forming.