期刊
ASTROPHYSICAL JOURNAL LETTERS
卷 739, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/739/2/L35
关键词
astrochemistry; evolution; ISM: abundances; ISM: clouds; ISM: molecules
资金
- ANR [09-BLAN-020901]
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.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据