Table 4.
Column density ratios in the CMZ of NGC 253 based on the ACA data.
| Isotopes | Ratio (a) | Proxy |
|---|---|---|
| 12C/13C | 13.3 ± 1.4 (b) | CO/13CO |
| 21.2 ± 1.5 | HCO+/H13CO+ | |
| 26.1 ± 1.3 | HCN/H13CN | |
| 17.4 ± 1.1 | HNC/HN13C | |
| 21 ± 2 | CN/13CN | |
| 23 ± 2 | CS/13CS | |
| 18 ± 4 | H2CO/H CO |
|
| 100 ± 10 | C18O/13C18O | |
| 46 ± 18 | CCH/13CCH | |
| 80 ± 20 | CCH/C13CH | |
| 60 ± 40 | CH3OH/13CH3OH | |
| 30 ± 40 | HC3N/HC13CCN | |
| 30 ± 40 | HC3N/H13CCCN | |
| 20 ± 30 | HC3N/HCC13CN | |
| 20 ± 7 | CH3CCH/CH CCH |
|
| 22 ± 3 | CH3CCH/CH3C13CH | |
| 40 ± 20 | CH3CCH/13CH3CCH | |
| 16O/18O | 48 ± 5 (b) | CO/C18O |
| 520 ± 60 | 13CO/ 13C18O | |
| 100 ± 20 | HCO+/HC18O+ | |
| 18O/17O | 8.7 ± 1.2 | C18O/C17O |
| 16O/17O | 400 ± 40 (b) | CO/C17O |
| 13 ± 4 | SiO/Si17O | |
| 14N/15N | 147 ± 15 | HCN/HC15N |
| 220 ± 50 | HNC/H15NC | |
| 32S/34S | 9.7 ± 0.5 | CS/C34S |
| 14 ± 4 | SO/34SO | |
| 28Si/29Si | 9 ± 4 | SiO/29SiO |
| 28Si/30Si | 40 ± 20 | SiO/30SiO |
Notes.
Isotopic ratios are based on the column density LTE fits which, though opacity corrected, is close to the optically thin regime. Higher opacity could result in ratios up to a factor of two larger (see Sect. 5.4 and Table 5).
This column density ratio has been re-calculated for a common source size of 10″ in order to match the size required to fit the main CO isotopologue emission (see Sect. 5.4)
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