Line ratio diagrams from CLOUDY AGN models for solar metallicity, α_ox = −1.4 with A_V = 10¹ mag (labeled as A, grid with dashed lines), and α_ox = −0.8 with A_V = 10^2.5 mag (labeled as B, grid with dash-dotted lines). Both grids span the full range of values explored in this work for the ionization parameter and the density, as shown in the legend and Fig. 3. The observed line ratios for W2246–0526 are indicated with a red square, or a red triangle for upper limits.