Distribution of the subsamples of galaxies across different diagnostic diagram. Top panels: Classical BPT diagrams (Baldwin et al. 1981), showing the distribution of O III/Hβ line ratio as a function of N II/Hα ratio (left panel), S II/Hα (middle panel), and O I/Hα (right panel). Solid and dot-dashed lines correspond to the demarcation lines proposed by K03 and K01 to distinguish between the different ionizing sources. Bottom panels: Diagrams comparing the distribution of Equivalent-width of Hα (WHα) as a function of (i) the N II/Hα ratio (left panel) WHaN diagram (Cid Fernandes et al. 2010; ii) the Hα velocity dispersion (σ_Hα, middle panel), WHaD diagram (Sánchez et al. 2024); and (iii) the O III/O II line ratio (right panel), proposed here as the WHaO diagram. In each panel, the black dots correspond to the full NMJ sample and each successive grey contour represents the area encircling the 90%, 65%, and a 15% of these points. The blue (red) contour represent the area that encircles 90% of the values corresponding to the LT (ET) subsamples of galaxies, as defined in the text. Finally, the location of the X-ray-selected AGNs are shown as dark-blue stars. The D parameter derived for a set of 2D KS-tests comparing the distributions of the different subsamples are included on top of each panel, using the nomenclature L/E when comparing LTGs versus ETGs, E/A for ETGs versus X-AGNs, and L/A for LTGs versus X-AGNs.