Ortho-to-para ratio of interstellar heavy water

C. Vastel 1, 2 C. Ceccarelli 3 E. Caux 1, 2 A. Coutens 3 J. Cernicharo 4 S. Bottinelli 5 K. Demyk 3 A. Faure 3 L. Wiesenfeld 3 Y. Scribano A. Bacmann 6 P. Hily-Blant 3 S. Maret 3 A. Walters 3 E. A. Bergin 7 G. A. Blake 8 Alain Castets 3 N. Crimier 3 C. Dominik 9 P. Encrenaz 10 M. Gérin 10, 11 P. Hennebelle 3 C. Kahane 3 A. Klotz 5, 12 G. Melnick 3 L. Pagani 10 B. Parise 5, 13 P. Schilke 14, 15 Valentine Wakelam 16 Alain Baudry 6 T. Bell 3 M. Benedettini 3 A. Boogert 3 S. Cabrit 10 P. Caselli 17 C. Codella 3 C. Comito 15 E. Falgarone 11 A. Fuente 3 P. F. Goldsmith F. Helmich 3 T. Henning 18 E. Herbst 19, 20 T. Jacq 6 M. Kama 3 W. Langer 3 B. Lefloch 3 D. Lis 3 S. Lord 3 A. Lorenzani 17 D. Neufeld 3 B. Nisini 21 S. Pacheco 3 Justin Pearson 3 T. Phillips 3 M. Salez 3 P. Saraceno 22 K. Schuster 3 X. Tielens 3 F. Van Der Tak 3 M. H. D. Van Der Wiel S. Viti 3 F. Wyrowski 23 H. Yorke 3 Ph. Cais 6 J. M. Krieg M. Olberg 24 L. Ravera 5
6 FORMATION STELLAIRE 2010
L3AB - Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux, OASU - Observatoire aquitain des sciences de l'univers, LAB - Laboratoire d'Astrophysique de Bordeaux [Pessac], Université Sciences et Technologies - Bordeaux 1
16 AMOR 2010
L3AB - Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux, OASU - Observatoire aquitain des sciences de l'univers, LAB - Laboratoire d'Astrophysique de Bordeaux [Pessac], Université Sciences et Technologies - Bordeaux 1
Abstract : Context. Despite the low elemental deuterium abundance in the Galaxy, enhanced molecular D/H ratios have been found in the environments of low-mass star-forming regions, and in particular the Class 0 protostar IRAS 16293-2422. Aims: The CHESS (Chemical HErschel Surveys of Star forming regions) key program aims to study the molecular complexity of the interstellar medium. The high sensitivity and spectral resolution of the Herschel/HIFI instrument provide a unique opportunity to observe the fundamental 11,1-00,0 transition of the ortho-D2O molecule, which is inaccessible from the ground, and determine the ortho-to-para D2O ratio. Methods: We detected the fundamental transition of the ortho-D2O molecule at 607.35 GHz towards IRAS 16293-2422. The line is seen in absorption with a line opacity of 0.62 ± 0.11 (1σ). From the previous ground-based observations of the fundamental 11,0-10,1 transition of para-D2O seen in absorption at 316.80 GHz, we estimate a line opacity of 0.26 ± 0.05 (1σ). Results: We show that the observed absorption is caused by the cold gas in the envelope of the protostar. Using these new observations, we estimate for the first time the ortho-to-para D2O ratio to be lower than 2.6 at a 3σ level of uncertainty, which should be compared with the thermal equilibrium value of 2:1. Herschel is an ESA space observatory with science instruments provided by European-led principal Investigator consortia and with important participation from NASA.
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https://hal.archives-ouvertes.fr/hal-00633418
Contributeur : Laurent Pagani <>
Soumis le : mardi 18 octobre 2011 - 14:45:34
Dernière modification le : mercredi 27 septembre 2017 - 01:21:52

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C. Vastel, C. Ceccarelli, E. Caux, A. Coutens, J. Cernicharo, et al.. Ortho-to-para ratio of interstellar heavy water. Astronomy and Astrophysics - A&A, EDP Sciences, 2010, 521, pp.L31. 〈10.1051/0004-6361/201015101〉. 〈hal-00633418〉

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