Correlations between NIR indices and velocity dispersion (upper panel), and between the indices (lower panel), as presented in Figs. 2 and 3 of Gasparri et al. (2021). Red lines represent the best-fitting linear relations derived by the authors, along with the corresponding Pearson correlation coefficients. Sample galaxies are colour-coded by morphological type and in the index-index plots, the symbol sizes are proportional to their central velocity dispersion. The values for IC 4296 are superimposed as a black square.