Galactic magnetic field and spiral arms against gas quenching due to Ram pressure

Abstract

Interaction between the intracluster medium (ICM) and the interstellar medium (ISM) plays a crucial role in galaxy evolution. Surveys of galaxy clusters have shown that ram pressure stripping (RPS) is a dominant mechanism that removes the cold gas reservoir from cluster galaxies. We extend the analytical model for ram pressure stripping by Singh et al. (2019) to include asymmetries in the disc, such as spiral arms and regular magnetic fields along the spiral arms. Non-thermal pressure from magnetic fields acts against the ram pressure and leads to greater gas retention in galaxies. Our analytical modelling of spiral galaxies with magnetic fields shows that a strong magnetic field, with a strength of $10^{-5}$ G, significantly enhances gas retention at the centre of a galaxy as it approaches the core of a cluster, thereby suppressing the stripping rates. We find that magnetic fields stronger than $10^{-6}$ G are critical for retaining gas all the way to the cluster centre. While both magnetic fields and galaxy mass contribute to the retention of gas, the influence of magnetic fields is particularly significant, especially in typical spiral galaxies where unusually high masses are not present. Our results may help in explaining why gas-rich galaxies can still be observed in dense cluster environments despite the strong stripping forces.