(U − B)_rest-mass diagram. In gray is shown the original (U − B)_rest-mass criterion as defined by Peng et al. (2010), and in cyan are highlighted the galaxies presenting a sSFR or emission lines in excess with respect to the passive cuts. The empty cyan histograms show the distribution of the contaminants with the old definitions, while the shaded cyan histograms show the distribution of the contaminants with the new selection criterion as defined in Sect. 4.5. The upper plot shows the diagram obtained for z ≤ 0.5, and the lower plot shows the diagram obtained for z > 0.5.