Electron temperature and density estimates. Top panel: diagnostic diagram employing line ratios sensitive to electron temperature (0.927 μm/1.257 μm, X axis) and density (1.600 μm/1.644 μm, Y axis). The grid displays a T_e range from 10 000 to 20 000 K (red solid lines), and an n_e range from 10 000 to 60 000 cm^-3 (blue dotted lines). Triangle and square indicate the logarithmic dereddened line ratios and uncertainties observed in the blue- and red-shifted HVC of the jet, respectively. Bottom panel: predicted 1.677 μm/1.644 μm [Fe ii] line ratio as a function of the electron density n_e. The solid curve corresponds to T_e = 17 500 K. The dashed horizontal lines show the range of ratios observed for the blue and the red lobe. The intersections between the curve and the dashed lines illustrate the range of n_e allowed by the ratios observed in the two lobes.