Diagnostic diagram introduced by Cid Fernandes et al. (2010) as an alternative to the BPT classification (see Fig. 1). A topological separation classifies galaxies into star forming galaxies (SF), strong and weak AGNs (sAGN and wAGN) and retired galaxies (RG; Cid Fernandes et al. 2011). We compute the two double-peak components of the merger candidates individually: we display the component dominating the [OIII]λ5008 line as triangles and the suppressed component as circles. We adapt the colour-coding according to the BPT classification in Fig. 1. We highlight galaxies with off-centred weak [OIII] lines by empty markers (Sect. 2.3). The majority of our classified components can be seen to be situated in the AGN region. A shift is also recognisable between the two components which correlates with the [OIII]λ5008 strength. The component dominating the [OIII] is more likely classified as a sAGN (45) and only some are wAGNs (13). The suppressed [OIII] component shows 26 sAGNs, 21 wAGNs, 8 SF and 4 RGs.