Water emission from the high-mass star-forming region IRAS 17233-3606^⋆,⋆⋆

High water abundances at high velocities

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: sleurini@mpifr.de
² LERMA, UMR 8112 du CNRS, Observatoire de Paris, École Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France
³ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
⁴ SRON Netherlands Institute for Space Research, PO Box 800, 9700 AV Groningen, The Netherlands
⁵ Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
⁶ Max-Planck-Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁷ Physics Department, The University, Durham DH1 3LE, UK
⁸ Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany

Received: 27 December 2013
Accepted: 18 March 2014

Abstract

We investigate the physical and chemical processes at work during the formation of a massive protostar based on the observation of water in an outflow from a very young object previously detected in H₂ and SiO in the IRAS 17233–3606 region. We estimated the abundance of water to understand its chemistry, and to constrain the mass of the emitting outflow. We present new observations of shocked water obtained with the HIFI receiver onboard Herschel. We detected water at high velocities in a range similar to SiO. We self-consistently fitted these observations along with previous SiO data through a state-of-the-art, one-dimensional, stationary C-shock model. We found that a single model can explain the SiO and H₂O emission in the red and blue wings of the spectra. Remarkably, one common area, similar to that found for H₂ emission, fits both the SiO and H₂O emission regions. This shock model subsequently allowed us to assess the shocked water column density, N_H2O = 1.2 × 10¹⁸ cm^-2, mass, M_H2O = 12.5  M_⊕, and its maximum fractional abundance with respect to the total density, x_H2O = 1.4 × 10^-4. The corresponding water abundance in fractional column density units ranges between 2.5 × 10^-5 and 1.2 × 10^-5, in agreement with recent results obtained in outflows from low- and high-mass young stellar objects.