One-dimensional velocity structure function. The structure function S₂ is plotted against the spatial lag l for all four observed gas tracers. The red, blue, yellow, and green lines correspond to the HISA, ¹³CO(1–0), [CI], and ¹³CO(3–2) data, respectively. The gray-shaded area is the spatial-resolution limit corresponding to the 46″ beam of the ¹³CO(1–0) data. The slopes are fitted outside that limit and are shown as dashed lines. The corresponding fit results are presented in the legend.