Table 2
Observed tracers and their corresponding critical and effective densities.
| Tracer | Eu ∕k(a) | ncrit(b) | neff(c) |
|---|---|---|---|
| (K) | (cm−3) | (cm−3) | |
| 13CO(1–0) | 5.3 | 720. | – |
| HCO+(1–0) | 4.3 | 6.8 × 104 | 9.5 × 102 |
| H13CO+(1–0) | 4.2 | 6.2 × 104 | 3.9 × 104 |
| HCN(1–0) | 4.3 | 4.7 × 105 | 8.4 × 103 |
| HNC(1–0) | 4.4 | 1.4 × 105 | 3.7 × 103 |
| HN13C(1–0) | 4.2 | 9.6 × 104 | – |
| N2H+(1–0) | 4.5 | 6.1 × 104 | 1.0 × 104 |
Notes. (a) Eu∕k are from the Cologne Database for Molecular Spectroscopy (CDMS, Müller et al. 2001, 2005; Endres et al. 2016). (b) ncrit are from Shirley (2015) assuming Tk = 10 K, except for 13CO(1–0) and HN13C(1–0), which were calculated following the method described by Shirley (2015). We also assume HN13C(1–0) shares the same collision rate coefficients as HNC. The relevant data used for the calculation are from Yang et al. (2010) and Dumouchel et al. (2010), and the Python script can be found at https://github.com/ZhiyuZhang/critical_densities. (c) neff assuming Tk = 10 K are from Shirley (2015).
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