期刊
ASTROPHYSICAL JOURNAL
卷 829, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.3847/0004-637X/829/2/102
关键词
dust, extinction; ISM: clouds; ISM: individual objects (Orion A, Rosette); ISM: structure; photon-dominated region (PDR)
资金
- NASA Einstein Postdoctoral Fellowship
- Harvard-MIT FFL Fellowship
We characterize the column-density probability distribution. functions (PDFs) of the atomic hydrogen gas, H I, associated with seven Galactic molecular clouds (MCs). We use 21 cm observations from the Leiden/Argentine/Bonn Galactic H I. Survey to derive column-density maps and PDFs. We find that the peaks of the H I. PDFs occur at column densities in the range. similar to 1-2 x 10(21) cm(-2) (equivalently, similar to 0.5-1 mag). The PDFs are uniformly narrow,. with a mean dispersion of sigma(Pi) (I) approximate to 10(20) cm(-2) (similar to 0.1 mag). We also investigate the H I-to-H-2. transition toward the cloud complexes and estimate H I. surface densities ranging from 7 to 16 M-circle dot pc(-2). at the transition. We propose that the H I. PDF is a fitting tool for identifying the H I-to-H-2. transition column in Galactic MCs.
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