Spatially resolved BPT diagrams of ESO 338 (see Fig. 10). The different colours represent different selections made in the BPT diagrams. Red: data points with a very high [O III]/Hβ ratio, selected in the SII diagram as being above the star formation line, but not originating in shocks log([S II]/Hα) < −0.8. Green: high ionization (log([O III]/Hβ) > 0.4), star formation dominated gas (selected in the [O I] diagram). Blue: data points which cover the same area in the [O I] diagram as the shock models of Allen et al. (2008) and are located above the star formation line. Pink: low-ionization (log([O III]/Hβ) < 0.4), star formation dominated gas selected in the [O I] diagram. Orange: nitrogen enhanced gas detected as high [N II]/Hα ratio in the [N II] diagram. Black: data points which do not fulfil any of the selection criteria. Bottom right panel: in greyscale the [O III]/[S II] line ratio, tracing the ionization (Fig. 7) with over-plottted the location of the different selections made in the BPT diagrams.