log(L_bol)–z plane with R shown as coloured dots (see colour bar at right). The black arrow points in the direction given by the PCA, evaluated in the bins within the black rectangle, while the dashed arrows show the uncertainty on the direction. The coloured rectangles highlight the bins of the parameter space shown in Fig. 8. We recall that the bins between 46.4 ≤ log(L_bol)≤47.4 and 1.0 ≤ z ≤ 2.8 are included in the SED evolution analysis described in Sect. 4.1.