2014MNRAS.438..444B

We investigate how ram pressure of intragroup and intracluster medium can influence the spatial and temporal variations of star formation (SF) of disc galaxies with halo masses (Mh) ranging from 10¹⁰ to 10¹²M_☉ (i.e. from dwarf irregular to Milky Way-type) in groups and clusters with 10¹³ ≤ Mh/M_☉ ≤ 10¹⁵ by using numerical simulations with a new model for time-varying ram pressure. The long-term evolution of SF rates and Hα morphologies corresponding to the distributions of star-forming regions are particularly investigated for different model parameters. The principal results are as follows. Whether ram pressure can enhance or reduce SF depends on Mh of disc galaxies and inclination angles of gas discs with respect to their orbital directions for a given orbit and a given environment. For example, SF can be moderately enhanced in disc galaxies with Mh = 10¹²M_☉ at the pericentre passages in a cluster with Mh = 10¹⁴M_☉ whereas it can be completely shut down (`quenching') for low-mass discs with Mh = 10¹⁰M_☉. Ram pressure can reduce the Hα-to-optical-disc-size ratios of discs and the level of the reduction depends on Mh and orbits of disc galaxies for a given environment. Disc galaxies under strong ram pressure show characteristic Hα morphologies such as ring-like, one-sided and crescent-like distributions.