Table 1
Molecular transitions detected from the NOEMA+30 m combined data toward DR18.
| Molecule | Transition | Rest frequency | θmaj × θmin | PA | Eu/k | Aul | ncr | 1σrms |
|---|---|---|---|---|---|---|---|---|
| (GHz) | (″×″) | (°) | (K) | (s–1) | (cm–3) | (mJy beam–1) | ||
| HCO+ | J = 1 – 0 | 89.189 | 3.33 × 2.65 | 12.55 | 4.28 | 4.19 × 10–5 | 1.69 × 105 | 7.416 |
| HCN | J = 1 – 0, F = 2 – 1(†) | 88.632 | 3.35 × 2.67 | 12.61 | 4.25 | 2.41 × 10–5 | 2.19 × 106 | 6.595 |
| HNC | J= 1–0 | 90.664 | 3.28 × 2.65 | 13.44 | 4.35 | 2.69 × 10–5 | 2.76 × 105 | 7.490 |
| C2H | N = 1 – 0, J = 3/2 – 1/2, F = 2 – 1(†) | 87.317 | 3.40 × 2.74 | 13.50 | 4.19 | 1.53 × 10–6 | 1.02 × 105 | 7.725 |
| H2CO |  |
72.838 | 4.04 × 3.19 | –162.77 | 3.50 | 8.15 × 10–6 | 1.51 × 105 | 9.469 |
| SiO | J=2–1 | 86.847 | 3.41 × 2.75 | 13.62 | 6.25 | 2.93 × 10–5 | 6.38 × 105 | 6.365 |
| N2H+ | J= 1–0 | 93.174 | 3.20 × 2.54 | –165.80 | 4.47 | 3.63 × 10–5 | 1.40 × 105 | 8.512 |
| HC3N | J = 8 – 7 | 72.784 | 4.04 × 3.19 | –162.77 | 15.72 | 2.94 × 10–5 | 1.10 × 106 | 9.454 |
| HC3N | J = 10 – 9 | 90.979 | 3.27 × 2.64 | 13.42 | 24.01 | 5.81 × 10–5 | 9.48 × 105 | 6.764 |
| H13CO+ | J= 1–0 | 86.754 | 3.42 × 2.75 | 16.70 | 4.16 | 3.85 × 10–5 | 1.55 × 105 | 6.162 |
| H13CN | J = 1 – 0, F = 2 – 1 | 86.340 | 3.43 × 2.76 | 13.66 | 4.14 | 2.23 × 10–5 | 2.03 × 106 | 6.836 |
| HN13C | J= 1–0 | 87.091 | 3.41 × 2.72 | 12.55 | 4.18 | 1.87 × 10–5 | 1.93 × 105 | 6.515 |
| 13CS | J=2–1 | 92.494 | 3.22 × 2.56 | 13.39 | 6.66 | 1.41 × 10–5 | 5.26 × 105 | 7.572 |
| DCN | J= 1–0 | 72.415 | 4.07 × 3.23 | –162.78 | 3.48 | 1.32 × 10–5 | 5.38 × 105 | 9.920 |
| DNC | J= 1–0 | 76.306 | 3.89 × 3.03 | –165.94 | 3.66 | 1.60 × 10–5 | 1.51 × 105 | 6.781 |
| NH2D |  |
85.926 | 3.45 × 2.77 | 13.51 | 20.68 | 1.76 × 10–5 | 3.79 × 106 | 7.757 |
Notes. For lines with hyperfine structure (hfs), the dagger (†) marks the frequency of one of the hfs components. The spectroscopic information on these transitions is taken from Jet Propulsion Laboratory (JPL)2 and the Cologne Database for Molecular Spectroscopy (CDMS)3 catalogs. The 1 σrms values are determined with a spectral resolution of 0.8 km s–1. The critical densities (ncr) are estimated with the collisional rates at a temperature of 10 K taken from the Leiden Atomic and Molecular Database (LAMDA) (van der Tak et al. 2020). The collisional rates of isotopologues and deuterated species are assumed to be the same as their main isotopologue. θmaj and θmin are the major and minor FWHM sizes of a beam, respectively. PA is the position angle (east of north) of a beam. Finally, Eu and Aul are the energy of the upper state for a chosen transition and the Einstein coefficient, respectively.
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