Bimodal d4000 distribution of galaxies as a function of stellar mass and redshift. Panels a–c show the d4000 distribution of VIPERS galaxies in 0.2 dex wide bins of stellar mass (coloured curves), colour coded as indicated for three redshift bins: 0.8–1.0, 0.65–0.80, and 0.50–0.65. Panel d does the same, but for galaxies at 0.02 ≤ z< 0.08 taken from SDSS-DR7. The curves become dotted in regions of parameter space below the 90% stellar mass completeness limits of the VIPERS survey, shown as the dashed curves in Fig. 2. For some stellar mass bins, the d4000 distributions are also shown via histograms with bins of width 0.05 in d4000. The y-axis scale indicates the fraction of galaxies within these bins of width 0.05 in d4000. The coloured numbers down the right-hand side indicate the number of galaxies in each stellar mass bin. The vertical dashed line indicates the d4000 = 1.55 limit used to separate the blue cloud and red sequence galaxy populations. Example Gaussian fits to the d4000 distributions of blue cloud and red sequence populations in a single mass bin are shown by the solid coloured areas.