Table 7
Interstellar C, N, O, and S isotope ratios.
| Molecule | CMZ | Inner disk | Local ISM | Outer Galaxy | Solar System (*) | |
|---|---|---|---|---|---|---|
| 12C/13C | C34S (a) | 27 ± 3 | 41 ± 9 | 66 ± 10 | 74 ± 8 | 89 |
| CN (b) | … | 44 ± 12 | 41 ± 11 | 66 ± 19 | ||
| C18O (c) | 24 ± 1 | 41 ± 2 | 60 ± 5 | 70 ± 10 | ||
| H2CO (d) | … | 40 ± 7 | 50 ± 13 | 64 ± 10 | ||
| average | 25 ± 2 | 42 ± 9 | 54 ± 10 | 69 ± 12 | ||
| 14N/15N | CN (e) | … | 269 ± 59 | 314 ± 104 | 289 ± 85 | 270 |
| HCN (f) | … | 284 ± 63 | 398 ± 48 | 388 ± 32 | ||
| HNC(f) | … | 363 ± 100 | 378 ± 79 | 395 ± 74 | ||
| N2H+ (g) | … | 900 ± 250 | 496 ± 65 | 581± 140 | ||
| NH3 (h) | 40 ± 13 | 175 ± 46 | 297 ± 99 | 96 ± 44 | ||
| 16O/18O | H2CO (i) | 263 ± 45 | 327 ± 32 | 560 ± 25 | 625 ± 144 | 490 |
| 18O/17O | CO (j) | 3.4 ± 0.1 | 3.6 ± 0.2 | 3.9 ± 0.4 | 4.8 ± 0.6 | 5.5 |
| 160/17O (**) | 894 ±155 | 1177 ± 132 | 2184 ± 244 | 3000 ± 786 | 2625 | |
| 32S/34S (a) | 19 ± 2 | 18 ± 4 | 24 ± 4 | 28 ± 3 | 23 | |
| 34S/33S (a) | 4.2 ± 0.2 | 4.3 ± 0.4 | 4.2 ± 0.5 | 4.1 ± 0.3 | 5.6 | |
| 32S/33S (a) | 70 ± 16 | 82 ± 19 | 88 ± 21 | 105 ± 19 | 127 | |
| 34S/36S (a) | 41 ± 4 | 122 ± 18 | 111 ± 16 | 161 ± 32 | 200 | |
| 32S/36S (a) | 884 ± 104 | 2382 ± 368 | 2752±458 | 4150 ± 828 | 4525 | |
Notes. The inner disk values refer to the mean values at galactocentric distances of 2.0 kpc ≤ RGC ≤ 6.0 kpc. The local ISM values refer to 7.5 kpc ≤ RGC ≤ 8.5 kpc. The outer Galaxy values point to 9.0 kpc ≤ RGC ≤ 11.0 kpc. (*)From Anders & Grevesse (1989). (a)This work. (b)From Savage et al. (2002) and Milam et al. (2005). (c)From Langer & Penzias (1990, Langer & Penzias 1993), Wouterloot & Brand (1996), and Keene et al. (1998). (d)From Henkel et al. (1980, 1982, 1983, 1985) and Yan et al. (2019). (e)From Adande & Ziurys (2012), Ritchey et al. (2015), and Fontani et al. (2015). (f)From Adande & Ziurys (2012) and Colzi et al. (2018) (g)From Ritchey et al. (2015). (h)From Chen et al. (2021). (i)From Gardner & Whiteoak (1981) and Wilson & Rood (1994). (j)From Zhang et al. (2020a). (**)The 16O/17O ratios are derived with values of 16O/18O and 18O/17O.
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