The impact of environment on the Fall relation

In a Lambda cold dark matter (DM) Universe, the stellar specific angular momentum (j) and the stellar mass (M) of a galaxy are tightly correlated as a consequence of the scaling existing for DM haloes. This correlation, a.k.a. Fall relation, is one of the most fundamental scaling relations of galaxies and represents a useful benchmark for analytical models and numerical simulations of galaxy formation and evolution. Indeed, galaxies living in dense environments, such as clusters and groups, and in filaments are affected by physical processes (e.g. mergers, ram pressure stripping, pre-processing) that leave indelible and distinct marks on their angular momentum and mass distributions. Thus, the Fall relation can be used as a powerful tool to get insights on the evolutionary path of galaxies in different environments. In particular, if pre-processing and ram pressure stripping are efficient in filaments, recently-accreted cluster members are expected to lie below the Fall relation of field galaxies.

We use a sample of star-forming galaxies in different environments (from field to cluster) and investigate their position in the j-M plane. These galaxies were observed with MUSE/VLT as part of the survey GASP (“Gas stripping phenomena in galaxies with MUSE”), which was designed to probe the galaxy disc up to 4-5 effective radii. This is essential to trace the whole angular momentum distribution of galaxy discs. Our sample includes both old and recently-accreted cluster members. We model the distribution and kinematics of the stellar and ionised gas components of our galaxies to extract robust rotation curves and surface density profiles, and we use these observables to calculate the stellar j and M of our galaxies. We find that our sample follows the Fall relation, with compelling implications for their evolutionary path based on the theoretical expectations.