Location of the Hα bright regions illustrated in Fig. 5 on BPT diagnostic diagrams. The coloured grid indicates the models for low metallicity SF galaxies from Levesque et al. (2010) (0 Myr instantaneous burst with n_e = 100 cm⁻³); the black dashed line shows for reference the extreme starburst line from Kewley et al. (2001). Circles and stars correspond to regions in Fig. 5; blue stars indicate regions located > 0.1 dex from the Levesque model grid in both diagrams; filled stars indicate regions with a high ratio of [OIII]5007/Hα (orchid) or [SII]6731/Hα (green).