BPT (Baldwin et al. 1981) diagram of the EW_Hα≥ 60 Å starburst galaxy candidate sample based on line peak intensity ratios. The solid red line is the empirical dividing line (a modified version of the equation given by Kauffmann et al. (2003a) shown in hatched green) between starburst galaxies (lower part, grey symbols) and galaxies containing an AGN contributing significantly to the flux in the strong emission lines (upper part, green dots). As a complementary AGN criterion we also used FWHM(Hα_em) > 540 km s^-1.