C. Ceccarelli 1, E. Caux 2, A. Castets 1, L. Loinard 1, S. Molinari 3, H. Smith 4, & G. White 6
1 Laboratoire d'Astrophysique, Observatoire de Grenoble, France
2 CESR CNRS-UPS, Toulouse, France
3 IPAC, Pasadena, USA
4 Harvard-Smithsonian Center for Astrophysics, Cambridge, USA
5 Queen Mary & Westfield College, London, UK
We present and analyse observations of several infrared lines of water obtained with the Long Wavelength Spectrometer (LWS) on board the Infrared Space Observatory (ISO) towards five low-luminosity protostars: IRAS16293-2422 in the rho-Ophiuchus complex, and SSV13,IRAS2, IRAS4 and IRAS6 in NGC1333. Those sources have similar bolometric luminosities, excite powerful outflows, and have their strongest continuum emission at far infrared or (sub-) millimetric wavelengths. They all belong to the youngest classes of stellar objects known: the Class 0 and I. In spite of their morphological and evolutionary similarity, the observations show large variations in their water line luminosities.
The water lines provide insight into three key areas of low-mass protostar formation: cloud chemistry and molecular/atomic abundances, cloud cooling mechanisms, and the shock environment. In this contribution we will consider the two main mechanisms of water line emission predicted in such young objects: thermal emission from their surrounding envelopes and emission from the shocks created by their powerful outflows. We will show in particular how the comparison of the ISO observations with ground-based data helps to clarify the origin of the water emission.