Odin observations of water in molecular outflows and shocks ^*,**,***

¹ Onsala Space Observatory, Chalmers University of Technology, 439 92 Onsala, Sweden e-mail: per.bjerkeli@chalmers.se
² SRON, Landleven 12, PO Box 800, 9700 AV Groningen, The Netherlands
³ Laboratoire de Radioastronomie - LERMA, École Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France
⁴ Swedish Space Corporation, PO Box 4207, 171 04 Solna, Sweden
⁵ CESR, Observatoire Midi-Pyrénées (CNRS-UPS), Université de Toulouse, BP 4346, 31028 Toulouse Cedex 04, France
⁶ Stockholm Observatory, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden
⁷ GEPI, Observatoire de Paris, CNRS, 5 Place Jules Janssen, 92195 Meudon, France
⁸ CESR, 9 Avenue du Colonel Roche, BP 4346, 31029 Toulouse, France

Received: 13 March 2009
Accepted: 26 August 2009

Abstract

Aims. We investigate the ortho-water abundance in outflows and shocks in order to improve our knowledge of shock chemistry and of the physics behind molecular outflows.

Methods. We used the Odin  space observatory to observe the H₂O() line. We obtain strip maps and single pointings of 13 outflows and two supernova remnants where we report detections for eight sources. We used RADEX  to compute the beam averaged abundances of o-H₂O relative to H₂. In the case of non-detection, we derive upper limits on the abundance.

Results. Observations of CO emission from the literature show that the volume density of H₂ can vary to a large extent, a parameter that puts severe uncertainties on the derived abundances. Our analysis shows a wide range of abundances reflecting the degree to which shock chemistry affects the formation and destruction of water. We also compare our results with recent results from the SWAS team.

Conclusions. Elevated abundances of ortho-water are found in several sources. The abundance reaches values as high as what would be expected from a theoretical C-type shock where all oxygen, not in the form of CO, is converted to water. However, the high abundances we derive could also be due to the low densities (derived from CO observations) that we assume. The water emission may in reality stem from high density regions much smaller than the Odin beam. We do not find any relationship between the abundance and the mass loss rate. On the other hand, there is a relation between the derived water abundance and the observed maximum outflow velocity.