Table 6.
Integrated intensity isotopic ratios toward NGC 253 in the literature.
| Isotopes | Ratio | Proxy | Beam | Reference |
|---|---|---|---|---|
| 12C/13C | 16 ± 3 | HCN/H13CN | 26″ | 1 |
| 10.7 ± 1.7 | HCO+/H13CO+ | 26″ | 1 | |
| 28 ± 6 | HNC/HN13C | 26″ | 1 | |
| 14 ± 3 (a) | CS/13CS | 16″ | 1 | |
| > 40 | CN/13CN | 22″ | 1 | |
| > 60 | C18O/13C18O | 23″ | 2 | |
| > 56 | CCH/13CCH | 14″ | 2 | |
| > 46 | CCH/C13CH | 14″ | 2 | |
| 36 (b) | CN/13CN | 22″ | 3 | |
| 13.7 ± 0.5 | HCN/H13CN | 24″ | 8 | |
| 14 ± 2 | HCO+/H13CO+ | 24″ | 8 | |
| 17 ± 1 | HNC/HN13C | 27″ | 8 | |
| 34 ± 2 | CS/13CS | 25″ | 8 | |
| 28 ± 2 (c) | CN/13CN | 24″ | 8 | |
| 10 − 20 | HCN/H13CN | 2″ | 11 | |
| 10 − 20 | HCO+/H13CO+ | 2″ | 11 | |
| 21 | C18O/13C18O | 3″ | 4 | |
| 19 − 53 (d) | CN/13CN | 2.5″ | 5 | |
| 16O/18O | ∼150 (e) | 13CO/C18O | 12″ | 6 |
| > 300 (e) | 13CO/C18O | 12 | 2 | |
| 130 | 13CO/13C18O | 3″ | 4 | |
| 69 ± 2 | HCO+/HC18O+ | 28″ | 8 | |
| 18O/17O | 10 | C18O/C17O | 16″ | 7 |
| ∼6.5 | C18O/C17O | 12″ | 6 | |
| 7.6 ± 0.5 | C18O/C17O | 23″ | 8 | |
| 4.5 | C18O/C17O | 3″ | 4 | |
| 16O/17O | ∼300 − 500 | CO | 2″ | 11 |
| 32S/34S | 16 | CS/C34S | 24″ | 9 |
| 8 | CS/C34S | 16″ | 9 | |
| 8 (e) | 13CS/C34S | 16″ | 10 | |
| > 16 (e) | 13CS/C34S | 16″ | 2 | |
| 7.5 ± 0.3 | CS/C34S | 24″ | 8 |
Notes.
With this line ratio, Henkel et al. (1993) (see their Sect. 5) estimated a column density ratio of > 40 on opacity grounds, under the assumption that previously measured CS/C34S∼8 by Mauersberger & Henkel (1989) should actually be equal to the average Galactic and solar system sulfur ratio of 23.
Based on a hyperfine structure derived opacity estimate of 0.5 for the main J = 2–1 feature, which results in an opacity corrected ratio of 40.
Column density ratio estimated using a fit to the CN profiles with MADCUBA (Martín et al. 2019a).
When corrected by an average estimated opacity based on the CN hyperfine structure the authors derive a ratio ranging 30 − 67, with notable difference between that at the emission peak (30 − 40) and the galaxy outskirts (47 − 67).
Indirect measurement using the 13C isotopologue and multiplying by an assumed 12C/13C ratio which differs among studies.
References. (1) Henkel et al. (1993, and references therein); (2) Martín et al. (2010); (3) Henkel et al. (2014); (4) Martín et al. (2019b); (5) Tang et al. (2019); (6) Harrison et al. (1999); (7) Sage et al. (1991); (8) Aladro et al. (2015); (9) Mauersberger & Henkel (1989); (10) Martín et al. (2006); (11) Meier et al. (2015).
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