2019MNRAS.486.2020D

We explore numerically the effects of mass inflow on barred spiral galaxies in the context of high-velocity clouds accreting on to galactic discs. To assess whether such events are detectable, we quantify their effect on the disc's gas distribution by calculating the lopsidedness parameter A₁, and by deriving position-velocity plots of H I emission. The impact of an accretion event strongly depends on the parameters of the high-velocity cloud. For cloud mass >=10⁷ M_☉, infall can have a lasting impact on the gaseous disc, with A₁ >= 0.05 for ∼1.5 Gyr. We discuss the time-variability of the lopsidedness parameter and consequences for detecting gas infall. Accretion events will be marginally noticeable in position-velocity diagrams, again depending on cloud parameters. Our models provide a possible explanation for low-amplitude lopsidedness observed in galaxies without nearby companions.