2016MNRAS.461.2630M

We use the eagle suite of cosmological hydrodynamical simulations to study how the H i content of present-day galaxies depends on their environment. We show that eagle reproduces observed H i mass-environment trends very well, while semi-analytic models typically overpredict the average H i masses in dense environments. The environmental processes act primarily as an on/off switch for the H i content of satellites with M_* > 10⁹ M_☉. At a fixed M_*, the fraction of H i-depleted satellites increase with increasing host halo mass M₂₀₀ in response to stronger environmental effects, while at a fixed M₂₀₀ it decreases with increasing satellite M_* as the gas is confined by deeper gravitational potentials. H i-depleted satellites reside mostly, but not exclusively, within the virial radius r₂₀₀ of their host halo. We investigate the origin of these trends by focusing on three environmental mechanisms: ram pressure stripping by the intragroup medium, tidal stripping by the host halo and satellite-satellite encounters. By tracking back in time the evolution of the H i-depleted satellites, we find that the most common cause of H i removal is satellite encounters. The time-scale for H i removal is typically less than 0.5 Gyr. Tidal stripping occurs in haloes of M₂₀₀ < 10¹⁴ M_☉ within 0.5 x r₂₀₀, while the other processes act also in more massive haloes, generally within r₂₀₀. Conversely, we find that ram pressure stripping is the most common mechanism that disturbs the H i morphology of galaxies at redshift z=0. This implies that H i removal due to satellite-satellite interactions occurs on shorter time-scales than the other processes.