BPT for all eDIG bins of IC1553, with the colours coding the vertical distance (both above and below) from the midplane. The plotted hybrid models correspond to 40% of the flux due to fast shocks with preionisation (curves lines) and with front shock only (blue curves), and 60% of the flux due to star formation with Z = Z_⊙ and q = 10⁷ cm/s. Solid curves correspond to the shock winds from 200 to 1000 km/s, and dashed curves represent magnetic field intensities from 0.0001 to 10 μG cm^3/2. The Kopsacheili et al. (2020) and Kewley et al. (2001) lines are also plotted, as in Figure 6.