Table 8
Mean values of column density and excitation temperature of CH3CN for different evolutionary classes in literature works.
| Reference |  |
Tex | θ(a) | Telescope | Type of sources |
|---|---|---|---|---|---|
| [cm−2] | [K] | [′′] | |||
| Hung et al. (2019) | 5.2 × 1015 | 102 | –(*) | SMT | EGO** |
| Giannetti et al. (2017b)(b) | 1.2 × 1013 | 33 | –(*) | IRAM 30 m, APEX, Mopra | 70 μm-weak |
| 3.5 × 1013 | 32 | –(*) | IR-weak | ||
| 4.4 × 1013 | 43 | –(*) | IR-bright | ||
| 7.4 × 1013 | 53 | –(*) | HII | ||
| Rosero et al. (2013)(c) | 8.0 × 1013 | 145 | 10 | SMT | HMPO |
| Purcell et al. (2006)(d) | 5.0 × 1012 | 30 | 36 | Mopra | No maser cores |
| 2.3 × 1013 | 55 | 36 | Maser cores | ||
| 3.0 × 1013 | 57 | 36 | UC HII | ||
| Araya et al. (2005)(e) | 4.4 × 1014 | 53 | 10 | SEST | UC HII |
Notes. (a) θ: assumed source size or the dimension of the beam if the emission has been assumed to fill the beam; (b) data of the cool component of methyl cyanide (for details see Giannetti et al. 2017b) taken from the VizieR On-line Data Catalog J/A+A/603/A33 (Giannetti et al. 2017a); (c) G34.26+0.15 has been excluded from the mean value beeing the only UC HII region in the sample; (d) data from the CH3CN(5K−4K) rotational diagram; (e)data from CH3CN(5K−4K), and of the lowest available (J+1)−J transition if 5−4 is not available; (*)corrected for beam dilution, evaluating the size of the emission of each source; (**) Extended Green Objects, emitting at 4.5 μm. This emission may come from H2 (ν = 0−0, S(9, 10, 11)) or CO (ν = 1−0) band heads which can be excited by shocks from protostellar outflows (Cyganowski et al. 2008).
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