[O iii]/[O ii] versus [Ar iv]/[Ar iii] (left), [O iii]/[O ii] versus [O i]/[O iii] (middle) and [O iii]/[O ii] versus He ii/Hβ (right) diagnostic diagrams. The red and blue points represent the DR10 and DR7 objects respectively. The curves represent our grid of models computed with the SED from PopStar models at an age of 1 Myr and with a metallicity 12 + log O/H = 8. The dashed lines link models with the same values of , the continuous lines link models with the same value of the trimming parameter f_Hβ, the ionization-bounded models corresponding to f_Hβ = 1. The key for the colors is given in the bottom right panel. Upper row of panels: our filled sphere models (f_S = 0.03), while the lower row corresponds to our bubble models (f_S = 3).