Shirazi & Brinchmann (2012) diagram including their AGN diagnostic (green dashed line). Blue squares represent the IMPs, whereas the position of their stack is shown as a black downward-facing open triangle. Red diamonds and yellow circles mark the AGN contaminated galaxies and star-forming objects classified as outliers (see text). The grey scale density diagram represents all eligible galaxies from the SDSS DR12 with AoN > 2 in the utilised emission lines, binned in 0.02 × 0.02 dex bins for the line ratios shown. Lower contrast indicates lower bin occupancy.