Gas phase Elemental abundances in Molecular cloudS (GEMS)
Astronomy and Astrophysics, vol. 646, pp. A5
Abstract
Context. Carbon monosulphide (CS) is among the most abundant gas-phase S-bearing molecules in cold dark molecular clouds. It is easily observable with several transitions in the millimeter wavelength range, and has been widely used as a tracer of the gas density in the interstellar medium in our Galaxy and external galaxies. However, chemical models fail to account for the observed CS abundances when assuming the cosmic value for the elemental abundance of sulfur. Aims. The CS+O → CO + S reaction has been proposed as a relevant CS destruction mechanism at low temperatures, and could explain the discrepancy between models and observations. Its reaction rate has been experimentally measured at temperatures of 150−400 K, but the extrapolation to lower temperatures is doubtful. Our goal is to calculate the CS+O reaction rate at temperatures <150 K which are prevailing in the interstellar medium. Methods. We performed ab initio calculations to obtain the three lowest potential energy surfaces (PES) of the CS+O system. These PESs are used to study the reaction dynamics, using several methods (classical, quantum, and semiclassical) to eventually calculate the CS + O thermal reaction rates. In order to check the accuracy of our calculations, we compare the results of our theoretical calculations for T ~ 150−400 K with those obtained in the laboratory. Results. Our detailed theoretical study on the CS+O reaction, which is in agreement with the experimental data obtained at 150–400 K, demonstrates the reliability of our approach. After a careful analysis at lower temperatures, we find that the rate constant at 10 K is negligible, below 10−15 cm3 s−1, which is consistent with the extrapolation of experimental data using the Arrhenius expression. Conclusions. We use the updated chemical network to model the sulfur chemistry in Taurus Molecular Cloud 1 (TMC 1) based on molecular abundances determined from Gas phase Elemental abundances in Molecular CloudS (GEMS) project observations. In our model, we take into account the expected decrease of the cosmic ray ionization rate, ζH2, along the cloud. The abundance of CS is still overestimated when assuming the cosmic value for the sulfur abundance.
Authors 40
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Affiliation as printed
Department of Physics, University of Firat, 23169 Elazig, Turkey
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Instituto de Física Fundamental
Affiliation as printed
Instituto de Física Fundamental (IFF-CSIC), C.S.I.C., Serrano 123, 28006 Madrid, Spain
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Universidad Autónoma de Madrid
Affiliation as printed
Departamento de Química-Física Aplicada, Unidad asociada IFF-UAM, Universidad Autónoma de Madrid 28049, Spain
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Centre National de la Recherche Scientifique · Institut des Sciences Moléculaires
Affiliation as printed
Institut des Sciences Moléculaires ISM), CNRS, Univ. Bordeaux, 351 cours de la Libération, 33400 Talence, France
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Affiliation as printed
Observatorio Astronómico Nacional (OAN-IGN), c/ Alfonso XII 3, 28014 Madrid, Spain
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Centre National de la Recherche Scientifique · Laboratoire d'Astrophysique de Bordeaux
Affiliation as printed
Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
Laboratoire d'astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
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Affiliation as printed
Observatorio Astronómico Nacional (OAN-IGN), c/ Alfonso XII 3, 28014 Madrid, Spain
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Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères
Affiliation as printed
Sorbonne Université, Observatoire de Paris, Université PSL, CNRS, LERMA, 92190 Meudon, France
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Center for Astrophysics Harvard & Smithsonian
Affiliation as printed
Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
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Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Centre for Astrochemical Studies, Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
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Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères
Affiliation as printed
Sorbonne Université, Observatoire de Paris, Université PSL, CNRS, LERMA, 92190 Meudon, France
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Centre National de la Recherche Scientifique · Laboratoire d'Astrophysique de Bordeaux
Affiliation as printed
Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
Laboratoire d'astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
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Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Centre for Astrochemical Studies, Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
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Affiliation as printed
Observatorio Astronómico Nacional (OAN-IGN), c/ Alfonso XII 3, 28014 Madrid, Spain
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Affiliation as printed
Observatorio Astronómico Nacional (OAN-IGN), c/ Alfonso XII 3, 28014 Madrid, Spain
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Affiliation as printed
Observatorio Astronómico Nacional (OAN-IGN), c/ Alfonso XII 3, 28014 Madrid, Spain
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Consejo Superior de Investigaciones Científicas · Centro de Astrobiología
Affiliation as printed
Centro de Astrobiología (CSIC-INTA), Ctra. de Ajalvir, km 4, Torrejón de Ardoz, 28850 Madrid, Spain
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Instituto de Radioastronomía Milimétrica
Affiliation as printed
Instituto Radioastronomía Milimétrica (IRAM), Av. Divina Pastora 7, Nucleo Central, 18012 Granada, Spain
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Yebes Observatory · Spanish National Observatory
Affiliation as printed
Observatorio Astronómico Nacional (OAN-IGN), c/ Alfonso XII 3, 28014 Madrid, Spain
Observatorio de Yebes (IGN), Cerro de la Palera s/n, 19141 Yebes, Guadalajara, Spain
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Affiliation as printed
Observatorio Astronómico Nacional (OAN-IGN), c/ Alfonso XII 3, 28014 Madrid, Spain
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Affiliation as printed
Observatorio Astronómico Nacional (OAN-IGN), c/ Alfonso XII 3, 28014 Madrid, Spain
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Instituto de Física Fundamental
Affiliation as printed
Instituto de Física Fundamental (IFF-CSIC), C.S.I.C., Serrano 123, 28006 Madrid, Spain
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Chalmers University of Technology
Affiliation as printed
Department of Space, Chalmers University of Technology, Earth and Environment, 412 93 Gothenburg, Sweden
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Affiliation as printed
Observatorio Astronómico Nacional (OAN-IGN), c/ Alfonso XII 3, 28014 Madrid, Spain
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Leiden University · Delft University of Technology
Affiliation as printed
Faculty of Aerospace Engineering, Delft University of Technology, Delft, University of Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands
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Lyon 1 Université · École Normale Supérieure de Lyon · Centre National de la Recherche Scientifique · Centre de Recherche Astrophysique de Lyon
Affiliation as printed
École Normale Supérieure de Lyon, CRAL, UMR CNRS 5574, Université Lyon I, 46 allée d’Italie, 69364, Lyon Cedex 07, France
École Normale Supérieure de Lyon, CRAL, UMR CNRS 5574, Université Lyon I, 46 allée d'Italie, 69364, Lyon Cedex 07, France
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Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Centre for Astrochemical Studies, Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
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Affiliation as printed
Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
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Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Centre for Astrochemical Studies, Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
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Center for Astrophysics Harvard & Smithsonian
Affiliation as printed
Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
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Consejo Superior de Investigaciones Científicas · Centro de Astrobiología
Affiliation as printed
Centro de Astrobiología (CSIC-INTA), Ctra. de Ajalvir, km 4, Torrejón de Ardoz, 28850 Madrid, Spain
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Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Centre for Astrochemical Studies, Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
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Affiliation as printed
Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
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Affiliation as printed
Observatorio Astronómico Nacional (OAN-IGN), c/ Alfonso XII 3, 28014 Madrid, Spain
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Instituto de Física Fundamental
Affiliation as printed
Instituto de Física Fundamental (IFF-CSIC), C.S.I.C., Serrano 123, 28006 Madrid, Spain
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University of Helsinki · University of Cologne
Affiliation as printed
Department of Physics, University of Helsinki, PO Box 64, 00014 Helsinki, Finland
Institute of Physics I, University of Cologne, Cologne, Germany
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National Radio Astronomy Observatory
Affiliation as printed
National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville VA 22901, USA
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Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
Centre for Astrochemical Studies, Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
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Instituto de Física Fundamental
Affiliation as printed
Instituto de Física Fundamental (IFF-CSIC), C.S.I.C., Serrano 123, 28006 Madrid, Spain
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
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