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Table A.1

Spectroscopic properties of the observed transitions.

Transition ncrit Eu/kB A B C
[cm-3] [K] [D2] [MHz] [MHz] [MHz]

SiO(5−4) 2.3 × 106 31.3 48.14651 ... 21 711.96 ...
DCN(3−2)  ~107 20.9 80.50709 ... 36 207.46 ...
13CO(2−1) 8.9 × 103 15.9 0.02437 ... 55 101.01 ...
C17O(2−1) 9.5 × 103 16.2 0.02432 ... 56 179.99 ...
CH3OH(5−1,5 − 4−1,4)-E 9.5 × 105 40.4 3.88240 127 484.0 24 679.98 23 769.70
CH3OH(50,5 − 40,4)-A+ 1.1 × 106 34.8 4.04297  − || −   − || −   − || − 
CH3OH(54,∗ − 44,∗)-A+/−a 3.5 × 105 115.2 1.45278  − || −   − || −   − || − 

Notes. Column (2) gives the critical density of the transition, ncrit = Aul/Cul, where Aul is the spontaneous decay rate and Cul is the collisional de-excitation rate. It was calculated at T = 15 K using the collisional-rate data available in the Leiden Atomic and Molecular Database (LAMDA; http://www.strw.leidenuniv.nl/~moldata/) (Schöier et al. 2005). For DCN, there is no molecular datafile available, so we used the collisional rate coefficient of HCN to estimate ncrit. Columns (3) and (4) give the upper-state energy and the product , where μel is the permanent electric dipole moment, and S is the line strength. Columns (5)–(7) list the rotational constants of the molecules. The data were compiled from the Jet Propulsion Laboratory (JPL; Pickett et al. 1998) and CDMS (Müller et al. 2005) databases.

(a)

A blend of CH3OH(54,1 − 44,0)-A+ and CH3OH(54,2 − 44,1)-A, which have the same spectroscopic parameters.

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