Open Access

Table 1.

Line excitation.

Frequency Eu/k (a) ncrit(b)
J (GHz) (K) (cm−3)
(1) (2) (3) (4) (5)

13CO 12CO
1–0 110.201 115.271 5.5 2e3
2–1 220.399 230.538 16.6 1e4
3–2 330.588 345.796 33.2 4e4
4–3 440.765 461.041 55.3 9e4
5–4 550.926 576.278 83.0 2e5
6–5 661.067 691.473 116.2 3e5
7–6 771.184 806.652 154.9 5e5
8–7 881.273 921.800 199.1 6e5

HCN HCO+

1–0 88.632 4.3 2e5
1–0 89.189 4.3 3e4
3–2 265.886 25.5 4e6
3–2 267.558 25.5 8e5

Notes. (a)Jansen (1995), Schöier et al. (2005); (b)Calculated for kinetic temperatures T kin ( CO ) = 100 $ T_{\mathrm{kin}}(\rm CO) = 100 $ K in the optically thin limit ignoring radiative trapping; Carilli & Walter (2013).

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.