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We have used the NIHAO (Numerical Investigation of a Hundred Astrophysical Objects) simulations to explore how supernovae (SNe) affect star formation in galaxies. We find that SN feedback operates on all scales from the interstellar medium (ISM) to several virial radii. SNe regulate star formation by preventing condensation of Hi into h 2 and by moving cold neutral gas to the hot Hii phase. The first effect explains why the cold neutral gas in dwarf galaxies forms stars inefficiently. The second maintains the hot ISM of massive galaxies (Hii vents out at lower masses). At |$v_{\rm vir}\lower.5ex{\,\, \buildrel\gt \over \sim \,\,}67{\rm \, km\, s}^{-1}$|⁠, the outflow rate follows the relation: |$\skew4\dot{M}_{\rm out}=23\, (v_{\rm vir}/67{\rm \, km\, s}^{-1})^{-4.6}\, {\rm SFR}$|⁠. |$20{{\ \rm per\ cent}}$| – |$70{{\ \rm per\ cent}}$| of the gas expelled from galaxies escapes from the halo (ejective feedback) but outflows are dominated by cold swept-up gas, most of which falls back on to the galaxy on a |${\sim } 1\,$| Gyr time-scale. This 'fountain feedback' reduces the masses of galaxies by a factor of 2–4, since gas spends half to three quarter of its time in the fountain. Less than |$10{{\ \rm per\ cent}}$| of the ejected gas mixes with the hot circumgalactic medium and this gas is usually not reaccreted. On scales as large as 6 r vir, galactic winds divert the incoming gas from cosmic filaments and prevent it from accreting on to galaxies (pre-emptive feedback). This process is the main reason for the low baryon content of ultradwarves. [ABSTRACT FROM AUTHOR]

We estimate the stellar mass that satellite galaxies lose once they enter groups (and clusters) by identifying groups in a high-resolution cosmological N-body simulation, assigning entry masses to satellite galaxies with halo abundance matching at the entry time and comparing the predicted conditional stellar mass function of satellite galaxies at z ≃ 0 with observations. Our results depend on the mass of the stars that form in satellite galaxies after the entry time. A model in which star formation shuts down completely as soon a galaxy enters a group environment is ruled out because it underpredicts the stellar masses of satellite galaxies even in the absence of tidal stripping. The greater is the stellar mass that can form, the greater the fraction that needs to be tidally stripped. The stellarmass fraction lost by satellite galaxies after entering a group or cluster environment is consistent with any value in the range 0-40 per cent. To place stronger constraints, we consider a more refined model of tidal stripping of galaxies on elongated orbits (where stripping occurs at orbit pericentres). Our model predicts less tidal stripping: satellite galaxies lose ~20-25 per cent of their stellar mass since their entry into the group. This finding is consistent with a slow-starvation delayed-quenching picture, in which galaxies that enter a group or cluster environment keep forming stars until at least the first pericentric passage. [ABSTRACT FROM AUTHOR]