ELGs in the ξ versus [N ii]/Hα diagram, colour coding PGs, LINERS, Seyferts and SF, as in Fig. 1. Also as in Fig. 1, orange points are sources with either or both of Hα and [N ii] weaker than 0.5 Å. Solid contours are for the full sample V, while the dashed ones are for galaxies with less than X₈ = 10 per cent of their flux at λ = 4020 Å due to populations younger than 10⁸ yr (for clarity, only the two outer contours are plotted in this case). Dotted horizontal lines mark a range of ×2 around the prediction of the RG model (ξ = 1).