Top panels: σ_[NII] against log([N II]/)Hα, log([S II]/)Hα, and log([O I]/)Hα, from left to right, obtained from the fitted total line profiles. The plotted measurements are colour-coded from purple to red, going from low to high flux ratios and line widths. Dashed and solid lines represent shock model grids from MAPPING V (Sutherland & Dopita 2017; Sutherland et al. 2018; see Fig. 16 for details). We assumed a one-to-one correlation between V_s and σ. For comparison, we also display the shock model predictions derived by Ho et al. (2014, dot-dashed red lines) and by Rich et al. (2011, magenta and purple curves, considering an 80% shock fraction); none of these predictions, derived assuming a pre-shock density of 10 cm⁻³ and different metallicities and magnetic field strengths (see Sect. 6.2.1 in Ho et al. 2014 and Sect. 7.1 in Rich et al. 2011 for details), match the majority of the Arp220 measurements. Bottom panels: Arp220 maps associated with the top panel diagrams, using the same colour codes.