Trend of Γ parameter (see Eq. (1)) as a function of velocity dispersion, for normal (mean stellar mass density Σ < 2500M_⊙ pc^-2) local ETGs (dark grey solid line) and for the whole local ETG population (long-dashed dark grey line). Dashed grey lines are the scatter around the best-fit relation of normal local ETGs, while grey open squares are the average values of the Γs of local normal ETGs in bin of ~50 km s^-1. Magenta points are the upper limits of Γ we have derived for high-z ETGs in our spectroscopic sample at ⟨ z ⟩ = 1.4, and magenta solid line is their best-fit relation (magenta dashed lines indicate the rms around the relation). The black small-dotted lines are the best-fit relations of 100 subsamples of local ETGs, randomly extracted from the local sample by Tortora et al. (2013), in order to have the same Σandσ_e distribution of our spectroscopic sample at ⟨ z ⟩ = 1.4 (filled dark grey squares are an example of one local subsample). In this procedure we excluded three galaxies of the high-z sample (identified with magenta points with a black contour) since the local sample is missing ETGs with similar Σ and σ_e. The black point indicates the typical error on Γs of our spectroscopic sample at ⟨ z ⟩ = 1.4.