WISE W1 − W2 vs. W2 − W3 diagram for the PSS-CSO (top) and the ECS (middle) sample. The symbols and colours have the same meaning as in Fig. 11. The dotted vertical demarcation lines are from Jarrett et al. (2017), the horizontal line marks the AGN threshold from Stern et al. (2012). Bottom: Histogram distributions of W2 − W3 for the PSS-CSO-G (blue) and ECS-G (green) galaxies with W1 − W2 < 0.8. Only sources with S/N > 5 in the bands W1 and W2 and with S/N > 3 in the band W3 are plotted.