The role of cosmic filaments in galaxy evolution

The main goal of this thesis is to shed light on the role of filaments in galaxy evolution. It is now well established that galaxies are distributed non-uniformly, and those that appear inside groups and clusters are redder, more massive, and less star-forming than those found in less dense environments. However, groups and clusters do not exist in isolation—they are embedded within an intricate web of filaments that link galaxy clusters and create large-scale structure, and the impact of filaments, which act as bridges in the large-scale structure, on galaxy evolution remains poorly understood.  One of the key challenges in establishing the role of filaments in galaxy evolution is identifying the filaments themselves and establishing which galaxies are filament members. Real data are subject to peculiar velocities distortions, and biases of observations, such as stellar mass incompleteness. Also, we typically assume that galaxies correctly reflect the underlying dark-matter filaments, even though galaxies are biased indicators of dark matter. Chapter 3 is dedicated to testing the reliability of the choice of galaxies as tracers of filaments and checking how the properties of galaxies, such as stellar mass, affect the reconstruction of underlying dark-matter filaments.  My main aim is to examine the impact of galaxy bias in filament identification.  I then focus on the role of filaments in affecting galaxy properties. I investigate whether filaments affect the cold gas content. While it is known that galaxies within dense environments, such as groups and clusters,  usually have less cold gas, controversial results have been reported for galaxies in filaments. Some studies found a deficiency of cold gas in galaxies within filaments, and others found an excess with respect to field galaxies of similar mass.  In Chapter 4, I investigate the gas content of galaxies in the Virgo Cluster and surrounding filaments, making use of observational data collected by the Virgo Filament Collaboration and model data drawn from the GAEA semi-analytical model. I test whether current state-of-the-art theoretical models can reproduce the observed gas properties of galaxies across different environments and understand the role of filaments in regulating the gas content of galaxies from a theoretical point of view. Finally, filaments are assumed to be a pathway of accretion of dark matter and gas into the groups. However, there is a lack of understanding of the role of filament in the evolution of groups of galaxies.  I examine the connection between quenching and the orientation of group members with respect to the central galaxies of their group, a phenomenon called anisotropic satellite galaxy quenching (ASGQ). I connect this phenomenon with the orientation of the filaments feeding the groups and, to a larger extent, to the large-scale structure.  To conclude, the role of cosmic filament in galaxy evolution is still debated. By combining observational and simulated data, this thesis addresses key unresolved questions in galaxy evolution as a function of the environment. My thesis sheds new light on the biases in the filament identification process using galaxies as tracers, offers insights into the impact of filaments on the gas content of galaxies, and links filament orientation to the quenching of galaxies in groups. These findings clarify the role of the filaments in galaxy evolution and provide a framework for future studies aimed at uncovering the intricate connection between galaxies and large-scale structure.