Left: same as Fig. 5 with the colour of each data point corresponding to the intrinsic UV slope β₀, ranging from  −2.32 to  −1.19. Data points lower than  −2.32 (resp. higher than  −1.19) are shown in dark blue (resp. dark red) allowing a wider dynamic range for the bulk of the data points. Right: intrinsic UV slope β₀ versus the perpendicular distance d_⊥. The Spearman correlation coefficient is ρ = 0.87.