BPT diagrams of [O III]λ5007/Hβ versus [N II]λ6584/Hα (left panel) and [O III]λ5007/Hβ versus ([S II]λ6717+[S II]λ6731)/Hα (right panel). Both panels show the diagrams for three different cuts as a function of the velocity dispersion measured on the Hα line (from top to bottom): < 30 km s⁻¹, between 30 and 70 km s⁻¹, and > 70 km s⁻¹. In the left panel, the dashed, dotted, dash-dotted, and solid lines represent the Kewley et al. (2001), Kauffmann et al. (2003), Stasińska et al. (2006), and Espinosa-Ponce et al. (2020) demarcation curves, respectively. In the right panel, the dashed, dotted, and solid lines represent the Kewley et al. (2001, 2006), and Espinosa-Ponce et al. (2020) demarcation curves, respectively. The size of the points in the left and right panels depends on the S/N measured at the peak of the [N II]λ6584 line and [S II]λ6717, respectively. Grey dots in the backgrounds correspond to all points in the sample.