Giraffe HR15N Th–Ar lamp line (black), and best-fit one-Gaussian (red) and two-Gaussian (blue) models. To facilitate comparison with earlier results the abscissa is shown on a velocity scale. Best-fit residuals, scaled up three times, are shown in green and orange for the one- and two-Gaussian models, respectively. The vertical dashed gray lines correspond to those shown in Fig. 17; the horizontal dotted lines indicate amplitudes in the residuals of ± 1% of peak, like the horizontal lines in Fig. 17.