Table 6
Estimate the beam filling factor ηbf(Tex) for different excitation temperatures, assuming that the 12CO(2–1) line is optically thick.
| Positions | ηbf(25 K) | ηbf(20 K) | ηbf(15 K) | ηbf(10 K) | ηbf(5 K) |
|
τ C18O | τ HCO + | τ HCN |
|
|
|
|
|||||||||||
| I(1) | 2.1 ×10-2 | 2.9 × 10-2 | 4.2 ×10-2 | 8.0 ×10-2 | 3.6 ×10-1 | 0.049 | 2.57 | 0.97 | |||
| I(2) | 7.4 ×10-3 | 9.9 × 10-3 | 1.5 ×10-2 | 2.8 ×10-2 | 1.2 ×10-1 | 0.033 | 0.021 | 0.012 | 1.77 | 0.67 | |
| I(3) | 3.9 ×10-3 | 5.2 × 10-3 | 7.7 ×10-3 | 1.5 ×10-2 | 6.6 ×10-2 | 0.056 | 0.038 | 2.97 | 1.12 | ||
| I-B(1) | 1.8 ×10-2 | 2.4 × 10-2 | 3.6 ×10-2 | 6.7 ×10-2 | 3.0 ×10-1 | 0.033 | 0.016 | 0.016 | 1.74 | 0.66 | |
| I-B(2) | 2.5 ×10-3 | 3.3 × 10-3 | 4.9 ×10-3 | 9.3 ×10-3 | 4.2 ×10-2 | 0.089 | 4.73 | 1.78 | |||
| 2d-a(1) | 5.1 ×10-3 | 6.7 × 10-3 | 1.0 ×10-2 | 1.9 ×10-2 | 8.5 ×10-2 | 0.059 | 3.12 | 1.18 | |||
| 2d-a(2) | 5.3 ×10-3 | 7.1 × 10-3 | 1.1 ×10-2 | 2.0 ×10-2 | 9.0 ×10-2 | 0.051 | 2.69 | 1.02 | |||
| 2d-b(1) | 8.9 ×10-3 | 1.2 × 10-2 | 1.8 ×10-2 | 3.3 ×10-2 | 1.5 ×10-1 | 0.018 | 0.97 | 0.37 | |||
| 2d-b(2) | 2.2 ×10-3 | 3.0 × 10-3 | 4.4 ×10-3 | 8.3 ×10-3 | 3.8 ×10-2 | 0.063 | 3.36 | 1.27 | |||
| 2d-b(3) | 1.9 ×10-3 | 2.6 × 10-3 | 3.8 ×10-3 | 7.2 ×10-3 | 3.2 ×10-2 | 0.135 | 7.16 | 2.70 | |||
| 2c-a(1) | 3.1 ×10-3 | 4.1 × 10-3 | 6.1 ×10-3 | 1.2 ×10-2 | 5.2 ×10-2 | 0.071 | 3.78 | 1.43 | |||
| 2c-a(2) | 2.7 ×10-3 | 3.7 × 10-3 | 5.4 ×10-3 | 1.0 ×10-2 | 4.6 ×10-2 | ||||||
| 2c-a(3) | 5.0 ×10-3 | 6.6 × 10-3 | 9.8 ×10-3 | 1.9 ×10-2 | 8.4 ×10-2 | ||||||
Notes. The next four columns provide the optical depths for 13CO(2–1), C18O(2–1), HCO+(1–0), and HCN(1–0) assuming an excitation temperature of 20 K and a beam filling factor equal to that derived from 12CO, i.e. ηbf(20 K). The next two columns provide the 12CO(2–1) column densities computed for two standard 12CO /13CO line ratios for the molecular ring (MR) and Galactic centre (GC) from Wilson & Rood (1994).
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