Top: [O iii] map (left) and Hα map with overplotted [O iii] contours (right). The colour ranges are 0.17–0.98 for Hα and 0.19–1.85 for [O iii], in units of 10^-16 erg cm^-2 s^-1.Bottom: [O i] λ6300 (left), and [S ii] λ6716 (right) maps, all with Hα contours overplotted. In the [SII] image we have indicated the transition region over which the [SII] over [NII] ratio increases from 2.3 to 3.5 see Sect. 4.2. The colour ranges are 0.015–0.288 for [O i] and 0.106–0.454 for [S ii], in units of 10^-16 erg cm^-2 s^-1. Colour bar at the bottom indicates the normalised colour range. E is top and N is right, and the FoV is 25.5′′    ×     25.5′′ (7.5    ×    7.5 pc²). The spatial PSF is about 3 spaxels in height and 2 spaxels width.