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Nitrogen isotopic ratios in Barnard 1: a consistent study of the N_2H^+, NH_3, CN, HCN, and HNC isotopologues

Daniel, F. and Gerin, M. and Roueff, E. and Cernicharo, J. and Marcelino, N. and Lique, F. and Lis, D. C. and Teyssier, D. and Biver, N. and Bockelée-Morvan, D. (2013) Nitrogen isotopic ratios in Barnard 1: a consistent study of the N_2H^+, NH_3, CN, HCN, and HNC isotopologues. Astronomy and Astrophysics, 560 . Art. No. A3. ISSN 0004-6361.

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Context. The ^(15)N isotopologue abundance ratio measured today in different bodies of the solar system is thought to be connected to ^(15)N-fractionation effects that would have occurred in the protosolar nebula. Aims. The present study aims at putting constraints on the degree of 15N-fractionation that occurs during the prestellar phase, through observations of D, ^(13)C, and ^(15)N-substituted isotopologues towards B1b. Molecules both from the nitrogen hydride family, i.e. N2H+, and NH3, and from the nitrile family, i.e. HCN, HNC, and CN, are considered in the analysis. Methods. As a first step, we modelled the continuum emission in order to derive the physical structure of the cloud, i.e. gas temperature and H_2 density. These parameters were subsequently used as input in a non-local radiative transfer model to infer the radial abundance profiles of the various molecules. Results. Our modelling shows that all the molecules are affected by depletion onto dust grains in the region that encompasses the B1-bS and B1-bN cores. While high levels of deuterium fractionation are derived, we conclude that no fractionation occurs in the case of the nitrogen chemistry. Independently of the chemical family, the molecular abundances are consistent with ^(14)N/^(15)N ~ 300, a value representative of the elemental atomic abundances of the parental gas. Conclusions. The inefficiency of the ^(15)N-fractionation effects in the B1b region can be linked to the relatively high gas temperature ~17 K, which is representative of the innermost part of the cloud. Since this region shows signs of depletion onto dust grains, we cannot exclude the possibility that the molecules were previously enriched in ^(15)N, earlier in the B1b history and that such an enrichment could have been incorporated into the ice mantles. It is thus necessary to repeat this kind of study in colder sources to test such a possibility.

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Lis, D. C.0000-0002-0500-4700
Additional Information:© 2013 ESO. Article published by EDP Sciences. Received 22 May 2013; accepted 20 September 2013. This work is based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). This work is based upon observations carried out at the Caltech Submillimeter Observatory, which is operated by the California Institute of Technology under cooperative agreement with the National Science Foundation (AST-0838261). This paper was partially supported within the programme CONSOLIDER INGENIO 2010, under grant Molecular Astrophysics: The Herschel and ALMA Era.- ASTROMOL (Ref.: CSD2009- 00038). We also thank the Spanish MICINN for funding support through grants AYA2006-14876 and AYA2009-07304.
Funding AgencyGrant Number
Institut national des sciences de l'Univers (INSU)UNSPECIFIED
Instituto Geográfico Nacional (IGN)UNSPECIFIED
ALMA Era.- ASTROMOLCSD2009-00038
Ministerio de Ciencia e Innovación (MICINN)AYA2006-14876
Ministerio de Ciencia e Innovación (MICINN)AYA2009-07304
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Subject Keywords:ISM: abundances; ISM: molecules; ISM: individual objects: Barnard 1; line: formation; astrochemistry; techniques: spectroscopic
Record Number:CaltechAUTHORS:20140128-132852910
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Official Citation:Nitrogen isotopic ratios in Barnard 1: a consistent study of the N2H+, NH3, CN, HCN, and HNC isotopologues F. Daniel, M. Gérin, E. Roueff, J. Cernicharo, N. Marcelino, F. Lique, D. C. Lis, D. Teyssier, N. Biver and D. Bockelée-Morvan A&A 560 A3 (2013) DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43538
Deposited By: Jason Perez
Deposited On:03 Feb 2014 21:17
Last Modified:03 Oct 2019 06:08

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