Left: diagnostic diagram to separate SFG, AGN and composite, comparing [O ii]λ3727/Hβ and [O iii]λ5007/Hβ. The starburst region is in the bottom-left part, while AGNs lie in upper-right part. The red line is the empirical separation by Lamareille et al. (2004) with 0.15 dex uncertainty. Right: MEx diagnostic diagram for our sample of emission-line galaxies. The diagram compares the excitation, that is, the emission line ratio [O iii]λ5007/Hβ, and the stellar mass M_∗. The violet curve is the empirical separation limit between starburst, AGN, and composite regions according to Juneau et al. (2014). In both diagrams, we mark, with blue squares, the four galaxies that lie completely (also including the errors) in the AGN region according to Lamareille et al. (2004).