BPT diagram of the 13 sources with prominent narrow emission lines in their optical spectra (FWHM (Balmer) < 500 km s⁻¹). The continuous curve denotes the star-forming and AGN division of Kauffmann et al. (2003), while the dashed curve the respective source separation of Kewley et al. (2001). Based on this scheme, all the sources fall in the AGN part (above the continuous curve), while four of them may also include contribution from star formation (between the curves).