The relationship between carbon monoxide abundance and visual extinction in interstellar clouds.
The relationship between carbon monoxide abundance and visual extinction in interstellar clouds.
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DOI：
10.1086/160451
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发表时间：
1982-11
期刊：
影响因子：
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通讯作者：
M. Frerking;W. Langer;R. Wilson
中科院分区：
文献类型：
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作者：
M. Frerking;W. Langer;R. Wilson
一氧化碳柱密度相比，对场星的rho Oph和金牛座分子云复合物的视觉反射。建立了C/sup 18/O柱密度与A/sub v/的关系，并给出了在20 mags以上目视观测范围内C/sup 13/CO柱密度的新的测定方法。提出并讨论了由CO同位素观测确定氢柱密度和分子云质量的方法。这些测量结果与气相化学模型（包括化学分馏和选择性同位素光破坏）的预测吻合得很好。C/sup 18/O柱密度对A/sub v/的功能依赖性的特点是由两个不同的制度分开的观察到发生在4 MAG的分子云复合物的一个明显的过渡，而/sup 13/CO的功能依赖性是完全不同的两个区域。我们发现，在高可见光消光时，C/sup 18/O发射出现一定的饱和，并使用更稀有的同位素物种C/sup 17/O和/sup 13/C/sup 18/O来校正它。
Carbon monoxide column densities are compared to visual extinctions toward field stars in the rho Oph and Taurus molecular cloud complexes. The relationship of C/sup 18/O column density to A/sub v/ is established, and new determinations for /sup 13/CO column densities are given for a range of visual extinctions extended to beyond 20 mag. A prescription for determining hydrogen column densities and masses of molecular clouds from observations of CO isotopes is presented and discussed critically. These measurements agree well with the predictions of gas phase chemistry models which include chemical fractionation and selective isotopic photodestruction. The functional dependence of the C/sup 18/O column density on A/sub v/ is characterized by two different regimes separated by a distinct transition observed to occur at 4 mag in both molecular cloud complexes, whereas the functional dependence of /sup 13/CO is quite different in the two regions. We find that some saturation occurs for C/sup 18/O emission at high visual extinction and use the rarer isotopic species C/sup 17/O and /sup 13/C/sup 18/O to correct for it.