Table 3
Estimated HCO+ column densities towards the source centre.
| Offseta | Transition | Velocity | T mb | FWHM | T ex | τ | N | N(HCO+)b |
( ) |
(km s-1) | (K) | (km s-1) | (K) | (1012 cm-2) | (1014 cm-2) | ||
|
|
||||||||
| 15.0, –7.5 | H13CO+J = 4–3 | 5.0 | 1.2 | 10.0 | 37.6 | 0.04 | 4.5 | 3.5 |
| 15.0, 0.0 | H13CO+J = 4–3 | 4.0 | 2.6 | 8.4 | 38.3 | 0.08 | 8.3 | 6.4 |
| 15.0, 7.5 | H13CO+J = 4–3 | 4.0 | 2.2 | 11.1 | 38.1 | 0.07 | 9.5 | 7.3 |
| 15.0, 15.0 | H13CO+J = 4–3 | 8.8 | 1.4 | 14.2 | 37.7 | 0.04 | 7.3 | 5.6 |
| 7.5, –15.0 | H13CO+J = 4–3 | 4.2 | 0.6 | 10.4 | 37.3 | 0.02 | 2.4 | 1.9 |
| 7.5, –7.5 | H13CO+J = 4–3 | 4.0 | 3.0 | 8.7 | 38.5 | 0.10 | 9.9 | 7.7 |
| 7.5, 0.0 | HC18O+J = 4–3 | 4.2 | 0.5 | 7.4 | 38.6 | 0.01 | 1.3 | 7.2 |
| 7.5, 7.5 | HC18O+J = 4–3 | 4.3 | 0.4 | 8.1 | 38.6 | 0.01 | 1.3 | 7.3 |
| 7.5, 15.0 | H13CO+J = 4–3 | 5.5 | 1.9 | 10.6 | 38.0 | 0.06 | 7.7 | 6.0 |
| 0.0, –15.0 | H13CO+J = 4–3 | 3.8 | 0.7 | 8.2 | 37.3 | 0.02 | 2.1 | 1.7 |
| 0.0, –7.5 | HC18O+J = 4–3 | 4.4 | 0.4 | 7.8 | 38.6 | 0.01 | 1.1 | 6.0 |
| 0.0, 0.0 | HC18O+J = 4–3 | 6.2 | 0.5 | 9.7 | 38.7 | 0.02 | 2.0 | 11. |
| 0.0, 7.5 | HC18O+J = 4–3 | 6.9 | 0.5 | 10.2 | 38.6 | 0.02 | 1.9 | 11. |
| 0.0, 15.0 | H13CO+J = 4–3 | 5.5 | 1.7 | 12.3 | 37.9 | 0.06 | 8.0 | 6.2 |
| –7.5, –15.0 | H13CO+J = 3–2 | 6.4 | 1.7 | 27.3 | 86.2 | 0.02 | 20. | 16. |
| –7.5, –7.5 | H13CO+J = 4–3 | 8.8 | 1.2 | 12.7 | 37.6 | 0.04 | 5.7 | 4.4 |
| –7.5, 0.0 | H13CO+J = 4–3 | 8.3 | 2.8 | 11.5 | 38.4 | 0.09 | 12. | 9.4 |
| –7.5, 7.5 | HC18O+J = 4–3 | 8.9 | 0.4 | 8.6 | 38.6 | 0.01 | 1.2 | 7.0 |
| –7.5, 15.0 | H13CO+J = 4–3 | 6.1 | 1.0 | 13.3 | 37.5 | 0.03 | 4.9 | 3.8 |
| –15.0, –15.0 | H13CO+J = 4–3 | 9.6 | 0.5 | 5.6 | 37.2 | 0.02 | 1.0 | 0.8 |
| –15.0, –7.5 | H13CO+J = 4–3 | 9.4 | 0.6 | 9.6 | 37.3 | 0.02 | 2.2 | 1.7 |
| –15.0, 0.0 | H13CO+J = 4–3 | 9.4 | 1.0 | 11.1 | 37.5 | 0.03 | 4.0 | 3.1 |
| –15.0, 7.5 | H13CO+J = 4–3 | 7.4 | 1.0 | 12.0 | 37.5 | 0.03 | 4.4 | 3.4 |
| –15.0, 15.0 | H13CO+J = 4–3 | 6.4 | 0.6 | 8.4 | 37.3 | 0.02 | 1.8 | 1.4 |
Notes. HCO+ column densities are calculated with RADEX assuming Tkin = 100 K and n(H2) = 2 × 106 cm-3. For the offset positions where HC18O+ was not detected, the data for H13CO+ J = 4−3 were used, except for (− 7.5′′, −15.0′′), where H13CO+ J = 4−3 was not detected and H13CO+ J = 3−2 was used. For the other positions, where all transitions were detected, data for the HC18O+ J = 4−3 transition are listed and we note that the column density determinations from the H13CO+ J = 4−3 line agree with these to within ± 50%.
based on 12C/13C = 77; 16O/18O = 560 (Wilson & Rood 1994).
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