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Herschel Survey of ...
Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
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- Indriolo, N. (author)
- Johns Hopkins University,University of Michigan
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- Neufeld, D.A. (author)
- Johns Hopkins University
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- Gerin, M. (author)
- Ecole Normale Superieure (ENS)
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- Schilke, P. (author)
- Universität zu Köln,University of Cologne
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- Benz, A.O. (author)
- Eidgenössische Technische Hochschule Zürich (ETH),Swiss Federal Institute of Technology in Zürich (ETH)
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- Winkel, B. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Menten, K.M. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Chambers, E.T. (author)
- Universität zu Köln,University of Cologne
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- Black, John H, 1949 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Bruderer, S. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Falgarone, E. (author)
- Ecole Normale Superieure (ENS)
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- Godard, B. (author)
- LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres, France
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- Goicoechea, J. R. (author)
- CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM)
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- Gupta, H. (author)
- California Institute of Technology (Caltech)
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- Lis, D. C. (author)
- LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres, France,California Institute of Technology (Caltech)
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- Ossenkopf, V. (author)
- Universität zu Köln,University of Cologne
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- Persson, Carina, 1964 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Sonnentrucker, P. (author)
- Space Telescope Science Institute (STScI)
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- van der Tak, F. F. S. (author)
- Rijksuniversiteit Groningen,University of Groningen,Netherlands Institute for Space Research (SRON)
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- van Dishoeck, E. F. (author)
- Universiteit Leiden (UL),Leiden University (UL),Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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- Wolfire, M. (author)
- University of Maryland
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- Wyrowski, F. (author)
- Max Planck Gesellschaft zur Förderung der Wissenschaften e.V. (MPG),Max Planck Society for the Advancement of Science (MPG)
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(creator_code:org_t)
- 2015
- 2015
- English.
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In: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 800:1, s. 40-
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Abstract
Subject headings
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- In diffuse interstellar clouds the chemistry that leads to the formation of the oxygen-bearing ions OH+, H2O+, and H3O+ begins with the ionization of atomic hydrogen by cosmic rays, and continues through subsequent hydrogen abstraction reactions involving H2. Given these reaction pathways, the observed abundances of these molecules are useful in constraining both the total cosmic-ray ionization rate of atomic hydrogen (ζH) and molecular hydrogen fraction (f_H_2). We present observations targeting transitions of OH+, H2O+, and H3O+ made with the Herschel Space Observatory along 20 Galactic sight lines toward bright submillimeter continuum sources. Both OH+ and H2O+ are detected in absorption in multiple velocity components along every sight line, but H3O+ is only detected along 7 sight lines. From the molecular abundances we compute f_H_2 in multiple distinct components along each line of sight, and find a Gaussian distribution with mean and standard deviation 0.042 ± 0.018. This confirms previous findings that OH+ and H2O+ primarily reside in gas with low H2 fractions. We also infer ζH throughout our sample, and find a lognormal distribution with mean log (ζH) = –15.75 (ζH = 1.78 × 10–16 s–1) and standard deviation 0.29 for gas within the Galactic disk, but outside of the Galactic center. This is in good agreement with the mean and distribution of cosmic-ray ionization rates previously inferred from H_3^+ observations. Ionization rates in the Galactic center tend to be 10-100 times larger than found in the Galactic disk, also in accord with prior studies.
Subject headings
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Publication and Content Type
- art (subject category)
- ref (subject category)
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- By the author/editor
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Indriolo, N.
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Neufeld, D.A.
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Gerin, M.
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Schilke, P.
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Benz, A.O.
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Winkel, B.
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show more...
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Menten, K.M.
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Chambers, E.T.
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Black, John H, 1 ...
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Bruderer, S.
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Falgarone, E.
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Godard, B.
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Goicoechea, J. R ...
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Gupta, H.
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Lis, D. C.
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Ossenkopf, V.
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Persson, Carina, ...
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Sonnentrucker, P ...
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van der Tak, F. ...
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van Dishoeck, E. ...
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Wolfire, M.
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Wyrowski, F.
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- About the subject
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- NATURAL SCIENCES
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NATURAL SCIENCES
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and Physical Science ...
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and Astronomy Astrop ...
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Astrophysical Jo ...
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Chalmers University of Technology