NW (left panel) and SE (right panel) outflow-integrated spectra extracted from the spaxels associated with high-velocity gas in the neutral and/or ionised phases (ΔV₀₂([O III]) <  −550 km s⁻¹ and/or ΔV₀₂(Na ID) <  − 900 km s⁻¹, for the NW system; ΔV₉₈([O III]) >  450 km s⁻¹ and/or ΔV₀₂(Na ID) <  − 750 km s⁻¹, for the SE galaxy; see Sect. 4.2). The shell-like region spaxels are not included in these integrated spectra. The stellar continuum emission has been previously modelled and subtracted from each spaxel. The red curves overplotted on the spectra represent the best-fit solutions that reproduce the line profiles; NC and OC Gaussians are also shown as in Fig. 2. The outflow-integrated spectra extracted from the original MaNGA datacube (hence without pPXF best-fit model subtraction) and the integrated pPXF best-fit spectra are also shown in the figure with solid and dotted grey curves, respectively. For the two grey curves we applied a downward shift for visualisation purposes.