Semi-analytic galaxies – II. Revealing the role of environmental and mass quenching in galaxy formation

We use the semi-analytic model of galaxy formation SAG on the MultiDark simulation MDPL2 to study the relevance of mass quenching and environmental quenching on passive satellite galaxies. We find that environmental processes dominate the star formation (SF) quenching of low mass satellites ($M_{\star} \lesssim 1.3 \times 10^{10}\, {\rm M}_{\odot}$), while mass quenching gains relevance on more massive galaxies ($M_{\star} \gtrsim 3 \times 10^{10}\, {\rm M}_{\odot}$), consistent with previous results in the literature. For a given stellar mass, SF quenching is less efficient in galaxies accreted by lower mass haloes both before and after first infall, because of the lower efficiency of both environmental and mass quenching processes, in contradiction with analysis of observational data. Quenching time-scales estimated for satellites that are active at first infall support the delay-then-rapid quenching scenario. The environment dominates the period of delayed quenching acting on the hot gas, while mass quenching is responsible for the fast decline of SF as the cold gas is consumed. The former stage is characterized by delay time-scales that range from $\approx 4\,{\rm Gyr}$ to $\approx 0.5\,{\rm Gyr}$ for low ($M_{\star} \approx 10^{10}\, {\rm M}_{\odot}$) and high ($M_{\star} \approx 10^{11}\, {\rm M}_{\odot}$) mass satellites, respectively. SF fading time-scales have the opposite trend with stellar mass, being $\approx 0.5\, {\rm Gyr}$ for low mass satellites and $\approx 2 \, {\rm Gyr}$ for high mass ones.