Left panel: mass-sSFR relation for MAC0416 cluster galaxies (blue symbols) and zCOSMOS field galaxies (green) at z ~ 0.4. The oblique solid thick black line shows the MS at z ~ 0.4 and its dispersion (indicated by the gray area), and the dashed red line depicts the local SDSS MS, using Eq. (1) in Peng et al. (2010a) for z ~ 0.4 and z ~ 0.06, respectively. Right panel: median values of the mass-sSFR relations at z ~ 0.4 are shown as blue (cluster) and green (field) solid lines and big symbols, while the corresponding dashed oblique lines enclose 68% of the data. The dashed thick light green line shows the completeness limit of our Zgals cluster sample, SFR ~ 0.3 M_⊙/yr.