Start time of the gas infall (left), gas infall timescale (middle), and outflow strength as indicated by the wind parameter factor (right) of our sample galaxies as functions of their stellar mass, obtained from best-fit models of the stacked spectra and SEDs. The results from galaxies in X-ray groups are shown with dark red lines, while galaxies in non-X-ray groups are shown in orange and field galaxies in blue. The shaded regions are 1σ scatters estimated from bootstrapping.