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


A. Coutens

Niels Bohr Institute

University of Copenhagen

C. Vastel

Centre national de la recherche scientifique (CNRS)

University of Toulouse

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

Netherlands Institute for Space Research (SRON)

University of Groningen

Carina Persson

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

P.E. Goldsmith

Jet Propulsion Laboratory, California Institute of Technology

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 1299-1313

Subject Categories

Astronomy, Astrophysics and Cosmology


Basic sciences


Onsala Space Observatory



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