SO line temperature ratio T_R(SO 10₁₁−10₁₀)/T_R(SO 9₈−8₇) versus intrinsic line temperature T_R(SO 9₈−8₇) predicted by RADEX slab models at T_K = 50, 500 K (black and red points/curves). Each curve corresponds to the labelled column density N_SO/ ΔV increasing from 10¹² to 10¹⁵ cm^-2 (km s^-1)^-1 by factors of 10 (left to right). Each dot along the curves corresponds to the labelled log(n_H2) (from 10⁵ to 10⁷ cm^-3). Optically thin models are marked with a cross, and optically thick models with a star. The black points indicate the upper limit of the SO line ratio and the SO 9₈−8₇ intensity corrected for beam dilution in the B2, B3, and R2 knots over the HV_jet velocity range.