The evolution of the cold gas fraction in nearby clusters ram-pressure stripped galaxies

Cluster galaxies are affected by the surrounding environment, which influences, in particular, their gas, stellar content and morphology. In particular, the ram-pressure exerted by the intracluster medium promotes the formation of multi-phase tails of stripped gas detectable both at optical wavelengths and in the sub-mm and radio regimes, tracing the cold molecular and atomic gas components, respectively. In this work we analyze a sample of sixteen galaxies belonging to clusters at redshift \(\sim 0.05\) showing evidence of an asymmetric HI morphology (based on MeerKAT observations) with and without a star forming tail. To this sample we add three galaxies with evidence of a star forming tail and no HI detection. Here we present the galaxies \(\rm H_{2}\) gas content from APEX observations of the CO(2-1) emission. We find that in most galaxies with a star forming tail the \(\rm H_{2}\) global content is enhanced with respect to undisturbed field galaxies with similar stellar masses, suggesting an evolutionary path driven by the ram-pressure stripping. As galaxies enter into the clusters their HI is displaced but also partially converted into \(\rm H_{2}\), so that they are \(\rm H_{2}\) enriched when they pass close to the pericenter, i. e. when they develop the star forming tails that are visible in UV/B broad bands and in H\(\alpha\) emission. An inspection of the phase-space diagram for our sample suggests an anticorrelation between the HI and \(\rm H_{2}\) gas phases as galaxies fall into the cluster potential. This peculiar behaviour is a key signature of the ram-pressure stripping in action.