[NeV]/[NeII] versus [NeIII]/[NeII] diagram. The five QSO2s are shown with the same symbols as in Fig. 3, and the six GATOS Seyfert galaxies from Zhang et al. (2024a) are shown as black crosses. The green dashed curve is the AGN photoionization model from Feltre et al. (2016) with gas metallicity Z = 0.017, density of gas cloud n_H = 10³ cm⁻³, dust-to-metal mass ratio ξ_d = 0.3, UV spectral index α = –1.7, and log U varying from –1.5 to –4.5 from top to bottom. Green contours are the full grid of AGN models from Feltre et al. (2016) with Z > 1/3 Z_⊙. Purple asterisks are AGN+SF models with 90% of star formation contribution to H_β, with log U increasing from –3 to 0 from left to right. Brown diamonds are AGN+shocks models with 90% of shock contribution to H_β, with shock velocity increasing from 200 to 1000 km s⁻¹ counterclockwise, pre-shock density of 100 cm⁻³, and transverse magnetic field strength  =  1 μG. Adapted from Fig. 5 in Feltre et al. (2023). See also Hermosa Muñoz et al. (2024).