Letter to the Editor

Odin water mapping in the Orion KL region^*

¹ Onsala Space Observatory (OSO), 439 92 Onsala, Sweden
² Stockholm Observatory, SCFAB, Roslagstullsbacken 21, 106 91 Stockholm, Sweden
³ Laboratoire d'Astronomie Spatiale, BP 8, 13376 Marseille Cedex 12, France
⁴ Department of Physics, University of Waterloo, Waterloo, ON N2L 3G1, Canada
⁵ LERMA & FRE 2460 du CNRS, Observatoire de Paris, 61 Av. de l'Observatoire, 75140 Paris, France
⁶ LERMA & FRE 2460 du CNRS, École Normale Supérieure, 24 rue Lhomond, 75005 Paris, France
⁷ NRC-HIA, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
⁸ Swedish Space Corporation, PO Box 4207, 171 04 Solna, Sweden
⁹ Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada
¹⁰ Observatory, PO Box 14, University of Helsinki, 00014 Helsinki, Finland
¹¹ Department of Physics and Astronomy. University of Calgary, Calgary, ABT 2N 1N4, Canada
¹² LESIA, Observatoire de Paris, Section de Meudon, 5 place Jules Janssen, 92195 Meudon Cedex, France
¹³ Metsähovi Radio Observatory, Helsinki University of Technology, Otakaari 5A, 02150 Espoo, Finland
¹⁴ Department of Astronomy and Physics, Saint Mary's University, Halifax, NS B3H 3C3, Canada
¹⁵ Swedish National Space Board, Box 4006, 171 04 Solna, Sweden
¹⁶ CESR, 9 avenue du Colonel Roche, BP 4346, 31029 Toulouse, France

Corresponding author: A. O. H. Olofsson, henrik@oso.chalmers.se

Received: 3 December 2002
Accepted: 14 February 2003

Abstract

New results from water mapping observations of the Orion KL region using the submm/mm wave satellite Odin (2.1´beam size at 557 GHz), are presented. The ortho-H₂O ground state transition was observed in a  rectangular grid with a spacing of 1´, while the same line of HOwas measured in two positions, Orion KL itself and 2´ south of Orion KL. In the main water species, the KL molecular outflow is largely resolved from the ambient cloud and it is found to have an extension of 60´´–110´´. The H₂O outflow profile exhibits a rather striking absorption-like asymmetry at the line centre. Self-absorption in the near (or “blue”) part of the outflow (and possibly in foreground quiescent halo gas) is tentatively suggested to play a role here. We argue that the dominant part of the KL HOoutflow emission emanates from the compact (size ~15´´) low-velocity flow and here estimate an H₂Oabundance of circa 10^-5 compared to all H₂ in the flow – an order of magnitude below earlier estimates of the H₂O abundance in the shocked gas of the high-velocity flow. The narrow ambient cloud lines show weak velocity trends, both in the N-S and E-W directions. HOis detected for the first time in the southern position at a level of ~0.15 K and we here estimate an H₂Oabundance of (1–8) .