Year: 2017
Type: article
Abstract: The abundance of H 2 in molecular clouds, relative to the commonly used tracer CO, has only been measured toward a few embedded stars, which may be surrounded by atypical gas. We present observations of near-infrared absorption by H 2 , CO, and dust toward stars behind molecular clouds, providing a representative sample of these molecules in cold molecular gas, primarily in the Taurus Molecular Cloud. We find ≈ 1.0 × 10 21 cm −2 , ≈ 1.5 × 10 17 cm −2 (1.8 × 10 17 including solid CO), and ≈ 6000. The measured ratio is consistent with that toward embedded stars in various molecular clouds, but both are less than that derived from millimeter-wave observations of CO and star counts. The difference apparently results from the higher directly measured ratio.
Source: The Astrophysical Journal
Authors: John H. Lacy, Christopher Sneden, Hwihyun Kim, Daniel T. Jaffe
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2599523944