Table 1
Transitions of H2CO observed with the IRAM 30-m and the APEX 12-m telescopes.
| Telescope | H2CO JKa,Kc | Frequency [GHz] | Eup/k [K] | Aij [s−1] | gup | ncrit [cm−3] | Detection rate [%] and noise [mK] | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cygnus-X 78 sources | GLOSTAR 12 sources | M8 37 sources | ||||||||||
| IRAM 30-m | 10,1 → 00,0 | 72.838 | 3.5 | 8.2(−6) | 3 | 2.8 ∙ 104 a | 100% | 30 | 100% | 23 | 95% | 30 |
| APEX | 30,3 → 20,2 | 218.222 | 21.0 | 2.8(−4) | 7 | 7.8 ∙ 105 a | 100% | 23 | 100% | 24 | 95% | 25 |
| APEX | 32,2 → 22,1 | 218.475 | 68.1 | 1.6(−4) | 7 | 3.2 ∙ 105 b | 83% | 96 | 92% | 72 | 49% | 53 |
| APEX | 32,1 → 22,0 | 218.760 | 68.1 | 1.6(−4) | 7 | 3.1 ∙ 105 b | 83% | 90 | 92% | 61 | 65% | 46 |
Notes. The rest frequencies, upper energies, and critical densities of the four observed transitions of H2CO. The detection rates for each line in each region are also presented. The Einstein coefficients are written in the form of A(−x) = A × 10−x. References. (a) Shirley (2015); critical density at T = 20 K. (b) Order of critical density estimated based on collisional rates of Wiesenfeld & Faure (2013), assuming optically thin conditions and considering p-H2 as the main collider. Molecular properties were taken from the Cologne Database for Molecular Spectroscopy (CDMS; Müller et al. 2001).
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