When many galaxies crowd together in a small space, the environment gets harsher and more stressful for them. As a result, they wear out more quickly and retire younger than their peers in less populated areas: their star formation is quenched rapidly. This is why in galaxy clusters we find a large fraction of early-type galaxies compared to late-type spirals, which are much more common in the field.
It has been known for a while that the responsible mechanisms for this early quenching, such as ram pressure stripping, galaxy-galaxy interactions, and starvation, play a significant role in removing the atomic gas from galaxies. If they are able to also directly affect the much more tightly bound and centrally located molecular gas, is less obvious. Since this gas is the direct fuel for star formation, this would have important implications for the evolution of cluster galaxies, and, with many galaxies residing in clusters and groups, galaxy evolution in the universe. With the ALMA Fornax Cluster Survey we study the molecular gas in Fornax cluster galaxies to find out whether the molecular gas in cluster galaxies can be removed directly through these processes, and how this affects their star formation.