Water deuterium fractionation in the high-mass star-forming region G34.26+0.15 based on Herschel/HIFI data
Journal article, 2014
Understanding water deuterium fractionation is important for constraining the mechanisms of water formation in interstellar clouds. Observations of HDO and H182O transitions were carried out towards the high-mass star-forming region G34.26+0.15 with the Heterodyne Instrument for the Far-Infrared (HIFI) instrument onboard the Herschel Space Observatory, as well as with ground-based single-dish telescopes. 10 HDO lines and three H182O lines covering a broad range of upper energy levels (22–204 K) were detected. We used a non-local thermal equilibrium 1D analysis to determine the HDO/H2O ratio as a function of radius in the envelope. Models with different water abundance distributions were considered in order to reproduce the observed line profiles. The HDO/H2O ratio is found to be lower in the hot core (∼3.5 × 10−4–7.5 × 10−4) than in the colder envelope (∼1.0 × 10−3–2.2 × 10−3). This is the first time that a radial variation of the HDO/H2O ratio has been found to occur in a high-mass source. The chemical evolution of this source was modelled as a function of its radius and the observations are relatively well reproduced. The comparison between the chemical model and the observations leads to an age of ∼105 yr after the infrared dark cloud stage.
astrochemistry ISM: abundances ISM: individual objects: G34.26+0.15 ISM: molecules
Author
A. Coutens
University of Copenhagen
Niels Bohr Institute
C. Vastel
University of Toulouse
Centre national de la recherche scientifique (CNRS)
U Hincelin
University of Virginia
E. Herbst
University of Virginia
D. Lis
California Institute of Technology (Caltech)
Pierre and Marie Curie University (UPMC)
L. Chavarría
University of Chile (UCH)
M. Gerin
Ecole Normale Superieure (ENS)
F. F. S. van der Tak
University of Groningen
Netherlands Institute for Space Research (SRON)
Carina Persson
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
P.E. Goldsmith
California Institute of Technology (Caltech)
E. Caux
University of Toulouse
Centre national de la recherche scientifique (CNRS)
Monthly Notices of the Royal Astronomical Society
0035-8711 (ISSN) 1365-2966 (eISSN)
Vol. 445 2 1299-1313Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Roots
Basic sciences
Infrastructure
Onsala Space Observatory
DOI
10.1093/mnras/stu1816