2019MNRAS.490.5375K

The difference in stellar metallicity between red and blue galaxies with the same mass constrains the time-scale over which red galaxies ceased to form stars. Here we investigate this constraint with the GALICS 2.0 semi-analytic model of galaxy formation. The advantage of this approach is that the time of pericentric passages for satellite galaxies and the mass-loading factor for galactic winds are not free parameters of the chemical evolution model. The former is determined by the N-body simulation used to construct the merger trees, the latter by the requirement that GALICS 2.0 should reproduce the stellar mass function of galaxies. When we compare our theoretical predictions with observations, we find that GALICS 2.0 can reproduce the observed metallicity difference only if quenching is preceded by a burst of star formation, which contributes to the chemical enrichment of the stellar population. Physically, this burst can be explained as tidally induced star formation or as an effect of ram pressure, which not only strips gas from galaxies but also compresses it, accelerating its conversion into stars.