age_f-redshift relations for the four mass bins. Solid and dotted curves (colour coded as in Fig. 10) are the ages of formation as a function of redshift referring, respectively to BC03 and MS11 spectral synthesis models. Dark-grey and light-grey shaded regions are the 1σ dispersions calculated starting from the 16th (P16) and 84th (P84) percentiles of the mass fraction cumulative function for BC03 and MS11 models, respectively.