VARIATIONS BETWEEN DUST AND GAS IN THE DIFFUSE INTERSTELLAR MEDIUM. II. SEARCH FOR COLD GAS

Journal Article · Sun Jan 01 00:00:00 EST 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/834/1/63· OSTI ID:22661433

Reach, William T. ^[1]; Heiles, Carl ^[2]; Bernard, Jean-Philippe ^[3]

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1. Universities Space Research Association, MS 232-11, Moffett Field, CA 94035 (United States)
2. Astronomy Department, University of California, Berkeley, CA 94720 (United States)
3. Université de Toulouse, Institut de Recherche en Astrophysique et Planétologie, F-31028 Toulouse cedex 4 (France)

The content of interstellar clouds, in particular the inventory of diffuse molecular gas, remains uncertain. We identified a sample of isolated clouds, approximately 100 M {sub ⊙} in size, and used the dust content to estimate the total amount of gas. In Paper I, the total inferred gas content was found significantly larger than that seen in 21 cm emission measurements of H i. In this paper we test the hypothesis that the apparent excess “dark” gas is cold H i, which would be evident in absorption but not in emission due to line saturation. The results show that there is not enough 21 cm absorption toward the clouds to explain the total amount of “dark” gas.

• OSTI ID: 22661433
• Journal Information: Astrophysical Journal, Vol. 834, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION
ABSORPTION SPECTRA
APPROXIMATIONS
ATOMS
CLOUDS
EMISSION
EMISSION SPECTRA
HYDROGEN
HYPOTHESIS
INTERSTELLAR SPACE
MOLECULES
SATURATION
VARIATIONS