Rest frequencies and upper level energies are adopted from the Cologne Database for Molecular Spectroscopy (CDMS, Müller et al. 2005), and the Leiden Atomic and Molecular Database (LAMDA, Schöier et al. 2005).

Beam size (resolution) used to create the respective map. This beam is ~6% larger than the actual HPBW at the corresponding frequencies, as defined by the kernel used in the gridding algorithm of GILDAS/CLASS.

Critical densities for temperature ranges 40–300 K (¹²CO, ¹³CO) and 10–30 K (HCN, HCN, HCO⁺, HCO⁺). As the main collisional transitions for HCN occur with ΔJ = 2, the traditional two-level formula for the critical density is not appropriate here. This formula generally overestimates the critical density. This also applies to the other molecules where ΔJ = 2 transitions are at least comparable. A better estimate for the actual population of the molecule is obtained here by adding the coefficients for ΔJ = 1 and ΔJ = 2.