Measurement of the PN’s expansion velocity. Left panel: Measurement of the X-shooter resolution (black points with error bars) from arc-lamp lines with the wavelength dependence modeled with a quadratic function (blue line, with the shaded region showing 1σ uncertainty). Right panel: The Hα line of the PN in the X-shooter spectra (emerald points). The error bars are too small to be seen here. The best-fit post-pixelized Gaussian profile is shown in red, while the width of the X-shooter LSF, as determined by the best fit in the left panel, is shown in blue for comparison. Both sets of illustrated datapoints are simultaneously fit to infer the PN’s expansion velocity σ_PN = 6.90 ± 0.49 km s⁻¹.