The Role of the Environment in Galaxy Evolution

Although the general picture of how galaxies have formed and evolved through cosmic time is already in place, still many details are missing. An example is represented by the role of environment in determining their observed properties. Local environment has been thoroughly explored through observations at low redshift and it has recently started to being investigated also in the distant Universe. Moreover, general attention has been increasingly focused on the cosmic web. This work explores how environment is observationally related to galaxy properties such as their stellar mass, their star-formation activity, or the presence of AGN phenomena in a large redshift range (0.2 < z < 3). To perform this study, both spectroscopic redshift data sets as well as photometric redshift surveys have been deployed. The picture that emerges is that high-density environments are favored places for galaxy evolution, showing an enhanced fraction of massive galaxies which have stopped forming stars. Galaxies in high-density environments have an increased probability of hosting radio-AGNs (belonging to the ensemble of processes that turn off the star-formation in massive galaxies) and these effects are visible since the start of the decline in the cosmic star-formation history. Large-scale structures, such as the filaments of the cosmic web, have also a role in shaping galaxy evolution and they may represent key places for the pre-processing of galaxies before they enter higher density regions such as the cluster or group environment. As an increasing amount of observational evidence on the relation between the evolution of galaxies and their environment is gathered, a complete solution to the problem of how the local galaxy population has evolved approaches, and the history of galaxies from their formation at the dawn of time to the present day gets closer to being traced.