Ortho-to-para ratio of interstellar heavy water
Journal article, 2010
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 1(1,1)-0(0,0) 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 (1 sigma). From the previous ground-based observations of the fundamental 1(1,0)-1(0,1) transition of para-D2O seen in absorption at 316.80 GHz, we estimate a line opacity of 0.26 +/- 0.05 (1 sigma). 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 3 sigma level of uncertainty, which should be compared with the thermal equilibrium value of 2:1.
constraints
line: identification
protostar iras 16293-2422
spectroscopy
submillimeter: ISM
ISM: molecules
envelope
molecular processes
astrochemistry
ISM: abundances
Author
C. Vastel
Paul Sabatier University
Institut National des Sciences de l'Univers
C. Ceccarelli
Institut National des Sciences de l'Univers
Grenoble Alpes University
Laboratoire d'Astrophysique de Bordeaux
E. Caux
Paul Sabatier University
Institut National des Sciences de l'Univers
A. Coutens
Institut National des Sciences de l'Univers
Paul Sabatier University
J. Cernicharo
Centro de Astrobiologia (CAB)
S. Bottinelli
Institut National des Sciences de l'Univers
Paul Sabatier University
K. Demyk
Institut National des Sciences de l'Univers
Paul Sabatier University
A. Faure
Grenoble Alpes University
L. Wiesenfeld
Grenoble Alpes University
Y. Scribano
U.M.R. 5209 C.N.R.S.
A. Bacmann
Institut National des Sciences de l'Univers
Laboratoire d'Astrophysique de Bordeaux
Grenoble Alpes University
P. Hily-Blant
Grenoble Alpes University
S. Maret
Grenoble Alpes University
A. Walters
Paul Sabatier University
Institut National des Sciences de l'Univers
E. A. Bergin
University of Michigan
G. A. Blake
California Institute of Technology (Caltech)
A. Castets
Institut National des Sciences de l'Univers
Grenoble Alpes University
Laboratoire d'Astrophysique de Bordeaux
N. Crimier
Grenoble Alpes University
Centro de Astrobiologia (CAB)
C. Dominik
Radboud University
Anton Pannekoek Institute for Astronomy
P. Encrenaz
Ecole Normale Superieure (ENS)
M. Gerin
Ecole Normale Superieure (ENS)
P. Hennebelle
Ecole Normale Superieure (ENS)
C. Kahane
Grenoble Alpes University
A. Klotz
Institut National des Sciences de l'Univers
Paul Sabatier University
G. J. Melnick
Harvard-Smithsonian Center for Astrophysics
L. Pagani
Ecole Normale Superieure (ENS)
B. Parise
Max Planck Society
P. Schilke
University of Cologne
Max Planck Society
V. Wakelam
Laboratoire d'Astrophysique de Bordeaux
Institut National des Sciences de l'Univers
A. Baudry
Laboratoire d'Astrophysique de Bordeaux
Institut National des Sciences de l'Univers
T. A. Bell
California Institute of Technology (Caltech)
M. Benedettini
Istituto di Fisica dello Spazio Interplanetario, Rome
A. Boogert
California Institute of Technology (Caltech)
S. Cabrit
Ecole Normale Superieure (ENS)
P. Caselli
University of Leeds
C. Codella
Arcetri Astrophysical Observatory
C. Comito
Max Planck Society
E. Falgarone
Ecole Normale Superieure (ENS)
A. Fuente
Spanish National Observatory (OAN)
P. F. Goldsmith
California Institute of Technology (Caltech)
F. Helmich
Netherlands Institute for Space Research (SRON)
T. Henning
Max Planck Society
E. Herbst
Ohio State University
T. Jacq
Laboratoire d'Astrophysique de Bordeaux
Institut National des Sciences de l'Univers
M. Kama
Anton Pannekoek Institute for Astronomy
W. D. Langer
California Institute of Technology (Caltech)
B. Lefloch
Grenoble Alpes University
D. Lis
California Institute of Technology (Caltech)
S. Lord
California Institute of Technology (Caltech)
A. Lorenzani
Arcetri Astrophysical Observatory
D. A. Neufeld
Johns Hopkins University
B. Nisini
Osservatorio Astronomico di Roma
S. Pacheco
Grenoble Alpes University
J. C. Pearson
California Institute of Technology (Caltech)
T. Phillips
California Institute of Technology (Caltech)
M. Salez
Ecole Normale Superieure (ENS)
P. Saraceno
Istituto di Fisica dello Spazio Interplanetario, Rome
K. Schuster
Institut de Radioastronomie Millimétrique (IRAM)
X. Tielens
Leiden University
F. F. S. van der Tak
University of Groningen
Netherlands Institute for Space Research (SRON)
M. H. D. van der Wiel
University of Groningen
Netherlands Institute for Space Research (SRON)
S. Viti
University College London (UCL)
F. Wyrowski
Max Planck Society
H. W. Yorke
California Institute of Technology (Caltech)
P. Cais
Laboratoire d'Astrophysique de Bordeaux
Institut National des Sciences de l'Univers
J. M. Krieg
Ecole Normale Superieure (ENS)
Michael Olberg
Chalmers, Earth and Space Sciences, Onsala Space Observatory
L. Ravera
Institut National des Sciences de l'Univers
Paul Sabatier University
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 521 1 Article Number: L31 - L31Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Roots
Basic sciences
DOI
10.1051/0004-6361/201015101