Intensity ratio between ¹²CO and ¹³CO radially averaged over the cone region: (a) as a function of the velocity on two slices of width = 0.7″ at δz = 2.2″ (black) and δz = 4.2″ (blue); and (b) as a function of height in the velocity bins (V − V_sys) = 2.15 km s⁻¹ (blue) and (V − V_sys) = 3.1 km s⁻¹ (black). The arrows represent the 5σ lower limit on the ratio when no ¹³CO is detected. (c) Resulting mass flux under different opacity hypothesis assuming optically thin ¹²CO (in red with errorbars at 30%), applying opacity correction based on ¹²CO/¹³CO and assuming either optically thin emission (lower limit: black solid) or the last detected value (upper limit: black dashed) when no ¹³CO is detected (see text for more details).