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Oxygen depletion in dense molecular clouds: a clue to a low O_2 abundance?

hal.structure.identifieraMOR 2011
dc.contributor.authorHINCELIN, U.
hal.structure.identifieraMOR 2011
dc.contributor.authorWAKELAM, Valentine
hal.structure.identifierFORMATION STELLAIRE 2011
dc.contributor.authorHERSANT, F.
hal.structure.identifieraMOR 2011
dc.contributor.authorGUILLOTEAU, S.
dc.contributor.authorLOISON, J. -C.
hal.structure.identifierUnivers, Théorie, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) [UTINAM]
dc.contributor.authorHONVAULT, P.
hal.structure.identifierInstitute of Physical Chemistry
dc.contributor.authorTROE, J.
dc.date.created2011
dc.date.issued2011-05
dc.date.conference2011
dc.description.abstractEnDark cloud chemical models usually predict large amounts of O2, often above observational limits. We investigate the reason for this discrepancy from a theoretical point of view, inspired by the studies of Jenkins and Whittet on oxygen depletion. We use the gas-grain code Nautilus with an up-to-date gas-phase network to study the sensitivity of the molecular oxygen abundance to the oxygen elemental abundance. We use the rate coefficient for the reaction O + OH at 10 K recommended by the KIDA (KInetic Database for Astrochemistry) experts. Our results show that the updates of rate coefficients and branching ratios of the reactions of our gas-phase chemical network, especially N + CN and H_3^+ + O, have changed the model sensitivity to the oxygen elemental abundance. In addition, the gas-phase abundances calculated with our gas-grain model are less sensitive to the elemental C/O ratio than those computed with a pure gas-phase model. The grain surface chemistry plays the role of a buffer absorbing most of the extra carbon. Finally, to reproduce the low abundance of molecular oxygen observed in dark clouds at all times, we need an oxygen elemental abundance smaller than 1.6× 10-4. To conclude, the chemistry of molecular oxygen in dense clouds is quite sensitive to model parameters that are not necessarily well constrained. That O2 abundance may be sensitive to nitrogen chemistry is an indication of the complexity of interstellar chemistry.
dc.language.isoen
dc.source.titleThe Molecular Universe, Posters from the proceedings of the 280th Symposium of the International Astronomical Union held in Toledo, Spain, May 30-June 3, 2011, #199 - IAU Symposium 280, Poster 44, Session 2. - 2011IAUS..280P.199H
dc.title.enOxygen depletion in dense molecular clouds: a clue to a low O_2 abundance?
dc.typeCommunication dans un congrès
dc.subject.halPlanète et Univers [physics]/Astrophysique [astro-ph]/Cosmologie et astrophysique extra-galactique [astro-ph.CO]
dc.subject.halPhysique [physics]/Astrophysique [astro-ph]/Cosmologie et astrophysique extra-galactique [astro-ph.CO]
bordeaux.page199P
bordeaux.volume280
bordeaux.conference.titleThe Molecular Univers
bordeaux.countryES
bordeaux.title.proceedingThe Molecular Universe, Posters from the proceedings of the 280th Symposium of the International Astronomical Union held in Toledo, Spain, May 30-June 3, 2011, #199 - IAU Symposium 280, Poster 44, Session 2. - 2011IAUS..280P.199H
bordeaux.conference.cityTolede
bordeaux.peerReviewedoui
hal.identifierhal-00606091
hal.version1
hal.invitednon
hal.proceedingsoui
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-00606091v1
bordeaux.COinSctx_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.btitle=The%20Molecular%20Universe,%20Posters%20from%20the%20proceedings%20of%20the%20280th%20Symposium%20of%20the%20International%20Astronomical%20Union%20held%20in%20Toledo,%2&rft.date=2011-05&rft.volume=280&rft.spage=199P&rft.epage=199P&rft.au=HINCELIN,%20U.&WAKELAM,%20Valentine&HERSANT,%20F.&GUILLOTEAU,%20S.&LOISON,%20J.%20-C.&rft.genre=unknown


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