Journal
ASTROPHYSICAL JOURNAL LETTERS
Volume 739, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/739/2/L35
Keywords
astrochemistry; evolution; ISM: abundances; ISM: clouds; ISM: molecules
Categories
Funding
- ANR [09-BLAN-020901]
Ask authors/readers for more resources
Interstellar dark clouds are the sites of star formation. Their main component, dihydrogen, exists under two states, ortho and para. H-2 is supposed to form in the ortho: para ratio (OPR) of 3:1 and to subsequently decay to almost pure para-H-2 (OPR <= 0.001). Only if the H-2 OPR is low enough, will deuteration enrichment, as observed in the cores of these clouds, be efficient. The second condition for strong deuteration enrichment is the local disappearance of CO, which freezes out onto grains in the core formation process. We show that this latter condition does not apply to DCO+, which, therefore, should be present all over the cloud. We find that an OPR >= 0.1 is necessary to prevent DCO+ large-scale apparition. We conclude that the inevitable decay of ortho-H-2 sets an upper limit of similar to 6 million years to the age of starless molecular clouds under usual conditions.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available