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Table 1

Molecular line transitions analyzed in this paper.

Molecule Transition Frequency (a) Velocity resolution EukB Critical density (b) rms noise (c)
(MHz) (km s−1) (K) ncrit (cm−3) (mJy beam−1)
13CO (d) 2–1 220 398.68 2.7 15.9 9.87 × 103 1.99 (d)
H2CO 30,3–20,2 218 222.19 0.5 21.0 3.36 × 106 5.29
32,2–22,1 218 475.63 0.5 68.1 2.96 × 106 4.58
CH3OH 4+2,2,0–3+1,2,0 218 440.05 0.5 45.5 7.81 × 107 4.95
CH3CN 120–110 220 747.26 0.5 68.9 4.46 × 106 4.06
121–111 220 743.01 0.5 76.0 4.13 × 106 4.06
122–112 220 730.26 0.5 97.4 4.19 × 106 4.06
123–113 220 709.02 0.5 133.1 4.27 × 106 4.06
124–114 220 679.29 0.5 183.1 3.96 × 106 4.06
125–115 220 641.08 0.5 247.3 3.62 × 106 4.06
126–116 220 594.42 0.5 325.8 3.68 × 106 4.06
DCN 30,0–20,0 217 238.54 2.7 20.9 1.82 × 107 1.76
SO 56–45 219 949.44 2.7 35.0 2.31 × 106 2.58

Notes. (a) The rest frequencies were extracted from the Cologne Database for Molecular Spectroscopy (CDMS). (b) The critical density was estimated from the approximation ncritA∕Γ (Shirley 2015), for collision rates at T = 100 K. Both, the Einstein A and the Γ coefficients were taken from the Leiden Atomic and Molecular Database (LAMDA). DCN is approximated by the corresponding values for HCN in the database. (c)The rms noise of the images was estimated from line-free channels. The beam size is 0.43′′ × 0.35′′. (d) Only for 13CO we also imaged the interferometric data merged with the single-dish data. The resulting cube has an rms noise of 2.15 mJy beam−1, with a synthesized beam of 0.8′′ × 0.67′′.

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