MUFASA: Time-scales for HI consumption and SFR depletion of satellite galaxies in groups

We investigate the connection between the HI content, star formation rate (SFR), and environment of galaxies using a hydrodynamic simulation that incorporates scaling relations for galactic wind and a heuristic halo mass based quenching prescription.We run two zoom-in simulations of galaxy groups with M_halo > 10¹³M⊙ at z = 0, selected to have quiet merger histories. We track galaxies as they become satellites, and compute the delay time τ_d during which the satellites are similar to central galaxies at a given stellar mass, and a fading time τf during which satellites go from gas-rich and star-forming to gas-poor and quiescent. We find 0.7 ≲ τ_d ≲ 3Gyr at z = 0, and depends inversely on the satellite halo mass at infall. At z ~ 1 we find ~0.3 ≲ τ_d ≲ 2Gyr, broadly consistent with a positive correlation with the Hubble time. For low halo mass at infall, lower stellar mass galaxies at infall time have higher τ_d. We generally find τf ≈ τ_d, ranging between ~150 Myr at z ~ 0 and ~80 Myr at z ~ 1 based on linear interpolation, with some uncertainty because they are smaller than our simulation output frequency (200.300 Myr). τf has no obvious dependence on infall halomass. Both time-scales show little difference between HI depletion and SF quenching, indicating that using up the gas reservoir by star formation without refilling is the main mechanism to transform satellite galaxies at these halo masses. At a given physical distance from the centre of the main halo of interest, higher redshift galaxies have on average higher cold gas content, but the ratio of gas (HI or H2) to SFR is similar, indicating that star formation is consistently fed through reservoirs of HI then H2. For a given amount of HI, galaxies have shorter consumption times in more massive halo structures at infall. Our results suggest that group-scale simulations naturally yield a delayed-then-rapid satellite quenching scenario as inferred from observations both today and at earlier epochs, though we highlight some quantitative discrepancies.