First detection of ND in the solar-mass protostar IRAS16293-2422

A. Bacmann 1 E. Caux 2, 3 P. Hily-Blant 4 B. Parise 5, 6 L. Pagani 7 S. Bottinelli 5 S. Maret 4 C. Vastel 2, 3 C. Ceccarelli 4 J. Cernicharo 8 T. Henning 9 Alain Castets 4 A. Coutens 4 E. A. Bergin 10 G. A. Blake 11 N. Crimier 4 K. Demyk 4 C. Dominik 12 M. Gerin 7, 13 P. Hennebelle 4 C. Kahane 4 A. Klotz 5, 14 G. Melnick 4 P. Schilke 15, 16 Valentine Wakelam 17 A. Walters 4 Alain Baudry 1 T. Bell 4 M. Benedettini 4 A. Boogert 4 S. Cabrit 7 P. Caselli 18 C. Codella 4 C. Comito 16 P. Encrenaz 7 E. Falgarone 13 A. Fuente 4 P. F. Goldsmith F. Helmich 4 E. Herbst 19, 20 T. Jacq 1 M. Kama 4 W. Langer 4 B. Lefloch 4 D. Lis 4 S. Lord 4 A. Lorenzani 18 D. Neufeld 4 B. Nisini 21 S. Pacheco 4 Justin Pearson 4 T. Phillips 4 M. Salez 4 P. Saraceno 22 K. Schuster 4 X. Tielens 4 F. F. S. Van Der Tak 23, 24 M. H. D. Van Der Wiel S. Viti 4 F. Wyrowski 25 H. Yorke 4 A. Faure 4 A. Benz O. Coeur-Joly 5 A. Cros 26 R. Güsten 16 L. Ravera 5
1 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
17 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. In the past decade, much progress has been made in characterising the processes leading to the enhanced deuterium fractionation observed in the ISM and in particular in the cold, dense parts of star forming regions such as protostellar envelopes. Very high molecular D/H ratios have been found for saturated molecules and ions. However, little is known about the deuterium fractionation in radicals, even though simple radicals often represent an intermediate stage in the formation of more complex, saturated molecules. The imidogen radical NH is such an intermediate species for the ammonia synthesis in the gas phase. Many of these light molecules however have their fundamental transitions in the submillimetre domain and their detection is hampered by the opacity of the atmosphere at these wavelengths. Herschel/HIFI represents a unique opportunity to study the deuteration and formation mechanisms of species not observable from the ground. Aims: We searched here for the deuterated radical ND in order to determine the deuterium fractionation of imidogen and constrain the deuteration mechanism of this species. Methods: We observed the solar-mass Class 0 protostar IRAS16293-2422 with the heterodyne instrument HIFI in Bands 1a (480-560 GHz), 3b (858-961 GHz), and 4a (949-1061 GHz) as part of the Herschel key programme CHESS (Chemical HErschel Survey of Star forming regions). Results: The deuterated form of the imidogen radical ND was detected and securely identified with 2 hyperfine component groups of its fundamental transition (N = 0-1) at 522.1 and 546.2 GHz, in absorption against the continuum background emitted from the nascent protostar. The 3 groups of hyperfine components of its hydrogenated counterpart NH were also detected in absorption. The absorption arises from the cold envelope, where many deuterated species have been shown to be abundant. The estimated column densities are ~2 × 1014 cm-2 for NH and ~ 1.3 × 1014 cm-2 for ND. We derive a very high deuterium fractionation with an [ND]/[NH] ratio of between 30 and 100%. Conclusions: The deuterium fractionation of imidogen is of the same order of magnitude as that in other molecules, which suggests that an efficient deuterium fractionation mechanism is at play. We discuss two possible formation pathways for ND, by means of either the reaction of N+ with HD, or deuteron/proton exchange with NH. 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-00633401
Contributeur : Laurent Pagani <>
Soumis le : mardi 18 octobre 2011 - 14:30:21
Dernière modification le : jeudi 28 septembre 2017 - 01:09:52

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A. Bacmann, E. Caux, P. Hily-Blant, B. Parise, L. Pagani, et al.. First detection of ND in the solar-mass protostar IRAS16293-2422. Astronomy and Astrophysics - A&A, EDP Sciences, 2010, 521, pp.L42. 〈10.1051/0004-6361/201015102〉. 〈hal-00633401〉

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