Table 6
Comparison with prototypical PDRs.
| Mon R2 | Ref | Orion Bar | Ref | NGC 7023 | Ref | Horsehead | Ref | |||
| (0″, 0″) | (+15″, −15″) | (0″, + 40″) | IF | (−25″, +40″) | PDR peak | |||||
|
|
||||||||||
| G0 (Habing) | 5 × 105 | 1, 2 | 2 × 104 | 3, 4 | 2 × 103 | 5 | 100 | 6, 7, 8 | ||
| n (cm-3)a | 4 × 106 | ~5 × 105 | ~2 × 105 | ~105 | ||||||
|
|
||||||||||
| H13CN /HN13C | 7.5 | 5 | 4 | 1 | > 2 | 3 | ||||
| HCN /HNC | 3 | 3 | 2 | 5 | ||||||
|
|
||||||||||
| 13CN/H13CN | < 4 | 2 | 5−12 | 1 | ||||||
| CN/HCN | 3.0 | 3 | 4.5 | 5 | ||||||
|
|
||||||||||
| H13CO+/H13CN | 0.29 | 0.40 | 0.37 | 1 | ||||||
| HCO+/HCN | 0.9 | 3 | 3.3 | 5 | ||||||
|
|
||||||||||
| CO+/H13CO+ | 0.53 | 1, 2 | 0.52 | 3, 4 | 0.6 | 4, 5 | < 0.03 | 6 | ||
| H13CO+/HOC+ | 5.8 | 1, 2 | 3.8 | 3, 4 | 5–14b | 4, 5 | ~4 | 6 | ||
|
|
||||||||||
| c-C3H2/C2H | 0.02 | 0.02 | 0.03 | 1 | 0.016 | 3, 4 | 0.03 | 4, 5 | 0.06 | 7 |
| C4H/C2H | 0.07 | 0.09 | 0.3 | 1 | 0.1 | 7 | ||||
| HCO/H13CO+ | <3 | <3 | 12 | 1 | 50c | 8, 9 | ||||
|
|
||||||||||
| SO+/SO | 0.1 | <0.06 | 1 | |||||||
| CS/HCS+ | 11d | 78d | 25d | 1 | 0.008 | 10 | ||||
Notes.
The density is not uniform in these regions. We indicate the representative density of the clumps/filaments.
It strongly depends on the position, varying between ~1 in the shielded core to ~50 in the HCO peak. The value in the table corresponds to the HCO peak derived from ~14″ angular resolution observations.
References. (1) This work; (2) Rizzo et al. (2003); (3) Fuente et al. (1996); (4) Fuente et al. (2003); (5) Fuente et al. (1993); (6) Goicoechea et al. (2009); (7) Teyssier et al. (2004); (8) Gerin et al. (2009a); (9) Gerin et al. (2009b); (10) Goicoechea et al. (2006).
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