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要旨:
We investigate the connection between the H i 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 Mhalo>1013M⊙ at z = 0, selected to have quiet merger histories. We track galaxies as they become satellites, and compute the delay time τd 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 ≲ τd ≲ 3 Gyr at z = 0, and depends inversely on the satellite halo mass at infall. At z ∼ 1 we find ∼0.3 ≲ τd ≲ 2 Gyr, 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 τd. We generally find τf ≪ τd, 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 halo mass. Both time-scales show little difference between H i 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 (H ı or H2) to SFR is similar, indicating that star formation is consistently fed through reservoirs of H ı then H2. For a given amount of H ı, 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.
