sSFR-Σ₁ sequence interpreted as an age–Σ₁ sequence. We show in a schematic diagram the sSFR vs. Σ₁ comparing the field with satellite galaxies in the mass range ﹩10.0\lt \mathrm{log}\,{M}_{\star }/{M}_{\odot }\lt 10.25﹩, based on Figure 4 of Woo et al. (2017). Interpreting the sSFR values for the QGs as stellar ages, one finds that denser QGs are older (the average trend indicated by the red lines). A flattening of the satellites’ relation can be caused by the additional contribution of environmental quenching, which appears to be able to switch off star formation in galaxies of lower Σ₁ relative to the field. In this paper, we seek to constrain the age distribution of QGs in the ﹩{{\rm{\Sigma }}}_{1}\mbox{--}{M}_{\star }﹩ plane.