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Table 1
Transition frequencies, upper energy levels, Einstein coefficients, and critical densities discussed in this work (sorted by frequencies).
| Species | Transition | Frequency | Eu ∕k | Aul |  |
Telescope | HPBW | Herschel |
|---|---|---|---|---|---|---|---|---|
| (GHz) | (K) | (s−1) | (cm−3) | /Instrument | (′′) | ObsID | ||
| CH+ | J = 5–4 | 4155.8719 | 599.6 | 1.05 | 8 × 1010 | Herschel/PACS | ~12 | 342218571/2 |
| CH+ | J = 4–3 | 3330.6297 | 400.1 | 0.53 | 2 × 1010 | /PACS | ~12 | 342218571/2 |
| CH+ | J = 3–2 | 2501.4404 | 240.3 | 0.22 | 5 × 109 | /PACS | ~12 | 342218571/2 |
| C+† | 2P3∕2–2P1∕2 | 1900.5369 | 91.3 | 2.3 × 10−6 | 4 × 103 | Herschel/HIFI | 12.0 | 1342250412/4/5 |
| o-H2O | 312–221 | 1153.1268 | 215.2 | 2.7 × 10−3 | ~6 × 107 | /HIFI | 19.8 | 1342250465 |
| 12CO | J = 10–9 | 1151.9854 | 304.2 | 1.0 × 10−4 | 1 × 106 | /HIFI | 19.8 | 1342250465 |
| HCN | J = 13–12 | 1151.4491 | 387.0 | 7.6 × 10−2 | 6 × 109 | /HIFI | 19.8 | 1342250465 |
| CH+ | J = 1–0 | 835.1375 | 40.1 | 6.2 × 10−3 | 1 × 108 | /HIFI | 27.3 | 1342250217 |
| HCO+ | J = 6–5 | 535.0616 | 89.9 | 1.2 × 10−2 | 3 × 107 | /HIFI | 42.6 | 1342244307 |
| CH | N, J = 1, 3/2–1, 1/2 | 532.7933 | 25.7 | 4.1 × 10−4 | ~3 × 108 | /HIFI | 42.8 | 1342244307 |
| HCN | J = 6–5 | 531.7164 | 89.3 | 7.2 × 10−3 | 7 × 108 | /HIFI | 42.8 | 1342244307 |
| A-CH3OH | 110,11–100,10 | 531.3193 | 153.1 | 6.8 × 10−4 | ~5 × 106 | /HIFI | 42.9 | 1342244307 |
| HCO+ | J = 3–2 | 267.558 | 25.7 | 1.4 × 10−3 | 4 × 106 | IRAM 30m/HERA | 9.2 | |
| 12CO‡ | J = 2–1 | 230.538 | 16.6 | 6.9 × 10−7 | 1 × 104 | /HERA | 10.7 | |
| 13CO‡ | J = 2–1 | 220.399 | 15.9 | 6.1 × 10−7 | 1 × 104 | /HERA | 11.2 | |
| C18O | J = 2–1 | 219.560 | 15.8 | 6.0 × 10−7 | 1 × 104 | /HERA | 11.2 | |
Notes. (a) Critical density, Aul ∕γul(Tk), in collisions with H2 at 100 K.
References. † Published in Goicoechea et al. (2015a). ‡Published in Berné et al. (2014).
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