Emission line diagnostic diagrams using [NII] /H_α and [OIII] /H_β line ratios for A983 and A1731 in the left and right panel, respectively. The dotted line separates the HII star-forming regions, below, from the AGN, above, following the modelling by Kewley et al. (2001). The selected AGN candidates are plotted as red asterisks. The triangle identifies the source without and [NII] emission lines. As a comparison, we also plotted the Kauffmann et al. (2003) cut as dashed line, that selects less fiercely star-forming galaxies.