Same line ratio diagram as Figure 3, but with the shock model grids (Allen et al. 2008) superposed. The AGN-dominated sources (PAH _6.2 μm EQW ⩽0.3 μm or [Ne v]/[Ne ii] ⩾1.0) are indicated with the red circles. The black crosses (×) denote the sources with at least one of the neon lines having a line width (FWHM) of >600 km s ⁻¹ (see also Section 4.2.2 and Figure 15 for details). The parameters of shock velocities V and the magnetic fields B increase with the directions of the arrows, in steps of 100, 200 km s ⁻¹ (the pink and red lines, respectively) and 1, 5, 10, 20, 40, 50, 100 μG (from the light blue to the dark blue lines), respectively.