Diagram of [O III]/Hβ compared to [S II]6717+6731/Hα (top) and [O III]5007/[O II]3727+3729 vs. [N II]6583/Hα (bottom) for 8 galaxies of our sample with optical spectra available and contemporary detection of [O III] and one between [S II]+Hβ or [O II]. The two diagrams are also called the S2 and the O2 BPT diagrams, respectively. As in the classical BPT diagram in Fig. 5, they show that our starbursts have different line excitation properties, and those with higher line velocity widths are generally shifted toward the AGN and LINER regions, according to empirical separation lines derived in the local (z ≲ 0.3) Universe.