Dereddened NLR ratios of [O III]/Hβ versus R_OIII for the same observational dataset as in Fig. 4. The gray dotted line consists of radiation pressure stratified ionization-bounded models with U_o = 0.1 assuming the Fg97 SED with T_cut = 10⁶ K. The frontal density along the sequence varies from up to 10⁷ cm⁻³, in steps of 0.5 dex (as in Fig. 7). The black line represents a similar density sequence but assuming a non-Maxwellian κ-distribution of electron kinetic energies with κ = 7. The light-green dashed arrows describe the change in R_OIII ratios resulting from the selected κ-distribution with κ = 7.