Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10701033 | Chinese Astronomy and Astrophysics | 2005 | 10 Pages |
Abstract
The MSX infrared dark cloud G79.2+0.38 has been observed over a 11â²Ãâ² region simultaneously in the J=1-0 rotational transition lines of the 12CO and its isotopic molecules 13CO and 18CO. The dense molecular cores defined by the C18O line are found to be associated with the two high-extinction patches shown in the MSX A-band image. The two dense cores have the column density N (H2) â¼ (5 - 12) à 1022 cmâ2 and the mean number density n â¼ (3 ± 1) à 104 cmâ3. Their sizes are 1.7 and 1.2 pc in 13CO(1-0) line, 1.2 and 0.6 pc in C18O(1-0) line, respectively. The masses of these cloud cores are estimated to be in the range from 2 à 102 to 2 à 103Mâ. The profile of radial mean density of the cloud core can be described by the exponential function ¯n(p) â¼ pâ0.34±0.02. Compared with the cases of typical optical dark clouds, the abundances of the CO isotopic molecules 13CO and C18O in this MSX infrared dark cloud appear to be depleted by a factor of 4-11, but at present there is no evidence for any obvious variation of the relative abundance ratio X13/18 between 13CO and C18O with the column density.
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Physical Sciences and Engineering
Physics and Astronomy
Astronomy and Astrophysics
Authors
Wu Ling-xiang, Yang Ji,