Colloquium – Gianluca Castignani: Processing of gas in galaxies within the cosmic web

Galaxies are distributed in a complex filamentary network of matter called the cosmic web. Several studies showed that galaxy properties can be influenced by their large scale environments: spiral galaxies may interact and merge into an elliptical galaxy, they can be stripped from their gas by ram pressure and see their star formation quenched, they can be harassed in small groups, even before entering into clusters. However, it remains debated which is the overall impact of the cosmic web in processing cold gas of galaxies, as they move through large-scale filaments around the clusters down to the densest regions of the cluster cores. To evaluate the degree of such processing it is essential to study the reservoirs of molecular gas as it is the raw material from which stars form. I will present the results of a large observational campaign, mainly exploiting IRAM millimeter facilities, with the goal of quantifying the processing of galaxies’ gas in the cosmic web and with cosmic time. I will discuss the degree of such processing in a variety of dense megaparsec-scale environments for: i) galaxies in the cosmological filaments around Virgo, the nearest cluster in the Universe, ii) galaxies in and around clusters at intermediate redshifts, iii) distant brightest cluster galaxies (BCGs) at the center of clusters. Finally, I will discuss the potential of such studies for next generation multi-wavelength facilities. Thousands of distant clusters and BCGs will be detected with Euclid, enabling an unprecedented leverage to constrain galaxy evolution in clusters.