Predictions for the wing intensity ratios between the observed ¹³CO lines and the ¹³CO J = 2–1 transition obtained from our non-LTE calculations for our three lines, J = 6–5, J = 10–9, and J = 16–15, dashed (black in electronic version), dotted (red), and dash-dot (green) lines. Intensity ratios are shown as functions of the kinetic temperature in the three panels for densities equal to 10⁷, 10⁶, and 10⁵ cm^-3.