Spearman correlation matrix for the physical and spectroscopic parameters considered. The lower-left half of squares show the Spearman correlation coefficient (ρ_c), color-coded from –1 (dark blue) to +1 (light brown), with the numerical values reported inside each cell. The upper-right half of squares show the associated p-values, color-coded according to significance level (from green for high significance to red for non–significant values). The diagonal reports the labels of the parameters. In addition to the parameters discussed in the previous sections, we also include [O/H] = 12+log(O/H) listed in Table 2.