Kinematic and environmental regulation of atomic gas in galaxies

This thesis investigated the removal of atomic cold gas (HI) from galaxies in dense cluster environments. A novel, angular momentum-based estimator was used to quantify the deficiency of HI. By applying this estimator to radio observations in the Virgo cluster and to numerical simulations, we found that cluster galaxies are strongly HI deficient and that this deficiency must have been caused by an external mechanism, such as stripping by the hot gas of the intra-cluster medium. Interestingly, the simulation reveals that only strongly stripped galaxies stop forming stars, because most of the stripping occurs at large non-star­forming radii.