Comparison between the observed spectrum and the fitted model for Fe II, Ni II, and Si II lines. The observed spectrum is shown with a blue line; errors bars reflect the uncertainties tabulated by the STIS pipeline (see Sect. 4.8). The solid orange line shows the reference spectrum. Absorptions from the LVCs, the disc, and the ISM are shown in dashed, solid, and dotted grey lines, respectively. The full model, convolved by the STIS LSF, is shown as a solid black line. Red ticks indicate the central velocities of the three LVCs, while the green tick at 0 km/s indicates the RV of the disc.