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Astron. Astrophys. 315, L181-L184 (1996)

Thermal H2O emission from the Herbig-Haro flow HH 54*

R. Liseau1,2, C. Ceccarelli3,2, B. Larsson1, B. Nisini2, G.J. White4, P. Ade4, C. Armand5, M. Burgdorf5, E. Caux6, R. Cerulli2, S. Church7, P.E. Clegg4, A. Di,Gorgio5,2, I. Furniss8, T. Giannini2, W. Glencross8, C. Gry5,9, K. King10, T. Lim5, D. Lorenzetti11, S. Molinari5,2, D. Naylor12, R. Orfei2, P. Saraceno2, S. Sidher5, H. Smith4, L. Spinoglio2, B. Swinyard10, D. Texier5, E. Tommasi2, N. Trams5, and S. Unger10

1 Stockholm Observatory, S-133 36 Saltsjöbaden, Sweden, (rene@astro.su.se)
2 CNR-Istituto di Fisica dello Spazio Interplanetario, Casella Postale 27, I-00044 Frascati (Rome), Italy
3 Laboratoire d'Astrophysique de l'Observatoire de Grenoble, 414, rue de la Piscine, BP 53, F-38041 Grenoble, France
4 Physics Department, Queen Mary & Westfield College, University of London, Mile End Road, London E1 4NS, UK
5 The LWSInstrument-Dedicated Team, ISOScience Operations Centre, P.O. Box 50727, E-28080 Madrid, Spain
6 Centre d'Etude Spatiale des Rayonnements, BP 4346, F-31029 Toulouse Cedex, France
7 California Institute of Technology, Pasadena, CA 91125, USA
8 Department of Physics and Astronomy, University College London, Gower Street, London, WC1 E 6BT, UK
9 Laboratoire d'Astronomie Spatiale, BP8, F-13376 Marseille Cedex 12, France
10 Space Science Department, Rutherford Appleton Laboratory, Chilton, Oxon OX11 OQX, UK
11 Osservatorio Astronomico di Roma, I-00044 Monteporzio, Italy
12 Department of Physics, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada

Received 2 July 1996 / Accepted 20 August 1996

Abstract. The first detection of thermal water emission from a Herbig-Haro object is presented. The observations were performed with the LWS (Long Wavelength Spectrograph) aboard ISO(Infrared Space Observatory). Besides H2O, rotational lines of CO are present in the spectrum of HH,54. These high-J CO lines are used to derive the physical model parameters of the FIR (far-infrared) molecular line emitting regions. This model fits simultaneously the observed OH and H2O spectra for an OH abundance X(OH) = 10-6 and a water vapour abundance X(H2O) = 10-5.

At a distance of 250,pc, the total CO, OH and H img2.gif Orotational line cooling rate is estimated to be 1.3 10-2Limg6.gif , which is comparable to the mechanical luminosity generated by the 10 km s-1 shocks, suggesting that practically all of the cooling of the weak-shock regions is done by these three molecular species alone.

Key words: stars: formation - ISM: molecules - ISM: jets and outflows - ISM: individual objects: HH,54 - physical processes: shock waves - physical processes: radiative transfer

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA (see: Kessler et al. 1996).

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