The impact of environment on galaxy evolution: starburst and AGN activity

This thesis aims to understand the processes driving galaxy evolution across a range of environments, focusing on submillimeter-radio interferometric observations to characterise the interstellar medium (ISM) of galaxies. I investigate the formation of the first massive, passive galaxies in clusters, as a key step towards establishing the prominent environmental trends seen at low redshift. Cl J1449+0856 is an excellent case to study this - a galaxy cluster at z=2 with an already virialised atmosphere. Thanks to the significant over-density of galaxies in Cl J1449+0856, we have uncovered a diverse range of cluster members at z=2. I use multi-wavelength observations to study how dust-obscured star-formation, ISM content and Active Galactic Nuclei (AGN) are linked to environment during this crucial phase of cluster evolution. I find that the dense cluster environment significantly increases the star-formation efficiency and gas excitation of the massive galaxies, and conclude that these effects are driven by the high number of mergers, interactions and AGN in the cluster core. I then examine the sub-M* population in the cluster, probing this important and so-far poorly characterised ISM regime. I place these low-enrichment galaxies on ISM scaling relations, and find evidence for increased gas-to-dust ratios in this regime at z=2, compared with the local Universe. I quantify the effect of low metallicity on high-J CO transitions, finding that both the diffuse and denser gas phases are significantly photo-dissociated at z=2. Finally, looking towards future surveys of obscured star-formation across all environments, I start preparations for the Square Kilometer Array (SKA). I construct high-resolution mock images of an entire survey field as observed by the SKA, containing galaxies with a variety of morphologies and star-formation rates at 0