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arXiv · 1902.08840

Oxygen fractionation in dense molecular clouds

Jean-Christophe Loison·Valentine Wakelam·Pierre Gratier·Kevin M. Hickson·Aurore Bacmann·Marcelino Agùndez·Nuria Marcelino·José Cernicharo·Viviana Guzman·Maryvonne Gerin·Javier R. Goicoechea·Evelyne Roueff·Franck Le Petit·Jérome Pety·Asunción Fuente·Pablo Riviere-Marichalar
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Abstract

We have developed the first gas-grain chemical model for oxygen fractionation (also including sulphur fractionation) in dense molecular clouds, demonstrating that gas-phase chemistry generates variable oxygen fractionation levels, with a particularly strong effect for NO, SO, O2, and SO2. This large effect is due to the efficiency of the neutral 18O + NO, 18O + SO, and 18O + O2 exchange reactions. The modeling results were compared to new and existing observed isotopic ratios in a selection of cold cores. The good agreement between model and observations requires that the gas-phase abundance of neutral oxygen atoms is large in the observed regions. The S16O/S18O ratio is predicted to vary substantially over time showing that it can be used as a sensitive chemical proxy for matter evolution in dense molecular clouds.

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Jean-Christophe Loison, Valentine Wakelam, Pierre Gratier, Kevin M. Hickson, Aurore Bacmann, Marcelino Agùndez, Nuria Marcelino, José Cernicharo, Viviana Guzman, Maryvonne Gerin, Javier R. Goicoechea, Evelyne Roueff, Franck Le Petit, Jérome Pety, Asunción Fuente, Pablo Riviere-Marichalar. 2019-02-23. Oxygen fractionation in dense molecular clouds. https://doi.org/10.1093/mnras%2Fstz560

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