Cumulative distribution functions illustrating the NH₃ (1, 1) linewidth (upper panel) and rotational temperature (lower panel) for the three largest subsamples in Table 6. The distribution of IRDCs from Peretto & Fuller (2009) is shown as a solid red line, the CH₃OH sample found within the large search radius is plotted as a dashed blue curve and the H II regions envelope as a dotted black curve.