Scatter density plots and corresponding histograms of the resulting values for α_OX and log U as obtained from HCM-TEFF assuming a stopping criterion of 99.9% of free electrons and with dust grains for the studied sample. The left panel shows those galaxies where the code used [O III], while the right panel shows the results using [S III]+[S IV]. The different symbols correspond to type 1 Seyferts or optical Seyferts (Sy1 or 1B in Spoon et al. 2022; red triangles), intermediate type Seyferts (Sy1.2 to Sy1.9; orange diamonds), hidden broad-line Seyferts (Sy1h; purple thin diamonds), type 2 Seyferts (Sy2; green squares), LINERs (blue circles), and IR-bright AGNs (1A, 2A, 2B, 3B in Spoon et al. 2022; grey crosses). The histograms also show the marginal distributions together with the mean values obtained in the resulting bimodal distributions.