Volume 521, October 2010
|Number of page(s)||7|
|Published online||01 October 2010|
Letter to the Editor
Laboratoire d'Astrophysique de Grenoble, UMR 5571-CNRS, Université Joseph Fourier, Grenoble, France
2 Université de Bordeaux, Laboratoire d'Astrophysique de Bordeaux, CNRS/INSU, UMR 5804, Floirac, France
3 Centre d'Étude Spatiale des Rayonnements, Université Paul Sabatier, Toulouse 3, CNRS UMR 5187, Toulouse, France
4 Max-Planck-Institut für Radioastronomie, Bonn, Germany
5 Department of Astronomy, University of Michigan, Ann Arbor, USA
6 California Institute of Technology, Pasadena, USA
7 Centro de Astrobiología, CSIC-INTA, Madrid, Spain
8 Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Amsterdam, The Netherlands
9 Department of Astrophysics/IMAPP, Radboud University Nijmegen, Nijmegen, The Netherlands
10 LERMA, UMR 8112-CNRS, Ecole Normale Supérieure et Observatoire de Paris, France
11 Max-Planck-Institut für Astronomie, Heidelberg, Germany
12 Harvard-Smithsonian Center for Astrophysics, Cambridge MA, USA
13 LERMA and UMR 8112 du CNRS, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France
14 Physikalisches Institut, Universität zu Köln, Köln, Germany
15 INAF – Istituto di Fisica dello Spazio Interplanetario, Roma, Italy
16 Infared Processing and Analysis Center, Caltech, Pasadena, USA
17 School of Physics and Astronomy, University of Leeds, Leeds UK
18 INAF Osservatorio Astrofisico di Arcetri, Florence Italy
19 IGN Observatorio Astronómico Nacional, Alcalá de Henares, Spain
20 Jet Propulsion Laboratory, Caltech, Pasadena, CA 91109, USA
21 SRON Netherlands Institute for Space Research, Groningen, The Netherlands
22 Ohio State University, Columbus, OH, USA
23 Johns Hopkins University, Baltimore MD, USA
24 INAF – Osservatorio Astronomico di Roma, Monte Porzio Catone, Italy
25 Institut de RadioAstronomie Millimétrique, Grenoble, France
26 Leiden Observatory, Leiden University, Leiden, The Netherlands
27 Kapteyn Astronomical Institute, University of Groningen, The Netherlands
28 Department of Physics and Astronomy, University College London, London, UK
Accepted: 2 September 2010
Nitrogen is the fifth most abundant element in the Universe, yet the gas-phase chemistry of N-bearing species remains poorly understood. Nitrogen hydrides are key molecules of nitrogen chemistry. Their abundance ratios place strong constraints on the production pathways and reaction rates of nitrogen-bearing molecules. We observed the class 0 protostar IRAS 16293-2422 with the heterodyne instrument HIFI, covering most of the frequency range from 0.48 to 1.78 THz at high spectral resolution. The hyperfine structure of the amidogen radical o-NH2 is resolved and seen in absorption against the continuum of the protostar. Several transitions of ammonia from 1.2 to 1.8 THz are also seen in absorption. These lines trace the low-density envelope of the protostar. Column densities and abundances are estimated for each hydride. We find that NH:NH2:NH3 ≈ 5:1:300. Dark clouds chemical models predict steady-state abundances of NH2 and NH3 in reasonable agreement with the present observations, whilst that of NH is underpredicted by more than one order of magnitude, even using updated kinetic rates. Additional modelling of the nitrogen gas-phase chemistry in dark-cloud conditions is necessary before having recourse to heterogen processes.
Key words: ISM: abundances / ISM: general / astrochemistry
Herschel is an ESA space observatory with science instruments provided by European-led principal Investigator consortia and with important participation from NASA.
Appendices (pages 6, 7) are only available in electronic form at http://www.aanda.org
© ESO, 2010
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.