Example of the fit that produces Fig. 5 for a single pixel. The data points from the cube are plotted in blue, the initial guess for the fit in dashed black, and the fit result is in red. The x-axis is in units of the cube velocity channels, where channel 200 corresponds to 0 km s⁻¹, and channelsare 0.5 km s⁻¹ apart. For this pixel the peaks are 0.785 K at − 21.6 km s⁻¹ (channel 156.7), and at 0.508 K at − 4.2 km s⁻¹ (channel 191.5).