Line diagnostic BPT diagrams log([OIII]_λ5007/Hβ) vs. log ([NII]_λ6583/Hα) (upper left panel) and log([OIII]_λ5007/Hβ) vs. log ([OI]_λ6300/Hα) (lower left panel) derived from MUSE pixels with S/N > 5. The different points are colour-coded according to their distance from the dashed lines defined by Kauffmann et al. (2003; upper panels) and Kewley et al. (2001; lower panels) to separate AGN from star forming regions. The grey contours show the distribution of a random sample of nuclear spectra of SDSS galaxies in the redshift range 0.01–1 and stellar mass 10⁹–10¹¹. The solid thick lines in the upper left panel show the expected behaviour of star forming regions as derived from the photo-ionisation models of Kewley et al. (2001) for three different metallicities (0.2, 0.4, 1 Z_⊙). Lower left panel: shock models of Rich et al. (2011) for increasing shock fraction (from left to right) in a twice solar gas. Right panels: distribution of the same points colour-coded as in the left panels over the disc of the galaxy. The cross shows the centre of the galaxy, the grey contours the distribution of the Hα emitting gas.