Morphological parameters vs. redshift (top panel) and mass (bottom panel) of all the clusters used in this work. High-z and Low-z sample clusters are colour-coded in blue and orange, respectively, following the sample colour code of Fig. 3. Left panels: centroid shift, ⟨w⟩. The solid red line is the mean ⟨w⟩ derived by Jeltema et al. (2008) from numerical simulations. The dotted lines correspond to the ±68% dispersion, Middle panel: concentration, C_SB. Right panel: M parameter. In each panel, the horizontal dotted line identifies the corresponding threshold, as defined in Fig. 3. The symbols ρ and p-value correspond to the Spearman’s rank correlation factor and the corresponding null hypothesis p-value, respectively. Errors on these quantities are computed through 1000 bootstrap resampling. The figure corroborates the lack of evolution with redshift of ⟨w⟩ and C_SB shown in Fig. 3. However, there is a mild but significant evolution of the combined parameter M. There is no dependence on mass of the morphological parameters.