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Astron. Astrophys. 338, L21-L24 (1998)

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Letter to the Editor

Detection of the "44 µm" band of water ice in absorption in combined ISO SWS-LWS spectra *

E. Dartois 1, P. Cox 1, P.R. Roelfsema 2, A.P. Jones 1, A.G.G.M. Tielens 2, L. d'Hendecourt 1, M. Jourdain de Muizon 3, B. Schmitt 4, T. Lim 5, B. Swinyard 6 and A. M. Heras 5

1 Institut d'Astrophysique Spatiale, Bât. 121, Université Paris XI, F-91405 Orsay Cedex, France
2 SRON, P.O. Box 800, 9700 AV Groningen, The Netherlands
3 LAEFF, E-28080 Madrid, Spain & DESPA, Observatoire de Paris, F-92190 Meudon, France
4 Laboratoire de Glaciologie et Géophysique de l'Environnement, CNRS, B.P. 96, F-38402 Grenoble/Saint-Martin d'Hères, France
5 ISO Science Operations Centre, Astrophysics Division of ESA, P.O. Box 50727, E-28080 Madrid, Spain
6 Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK

Received 20 July 1998 / Accepted 12 August 1998


We report the detection of the transverse optical vibrational band of water ice at 44 µm in absorption towards two embedded infrared sources, IRAS 18316-0602 (RAFGL7009S) and IRAS 19110+1045. The water band extending from 30 to about 80 µm is a prominent feature in the combined ISO SWS and LWS grating spectra. Using new optical constants for amorphous and crystalline water ice, we have modeled the infrared spectra of the two embedded sources with a radiative transfer code. Most of the observed absorption bands are well fit by H2O, CO, and CO2 ice mantles on silicate and graphite cores.

Key words: ISM: dust, extinction – ISM: individual objects – infrared: ISM: continuum – infrared: ISM: lines and bands

* 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

Send offprint requests to: E. Dartois (e-mail: dartois@ias.fr)

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© European Southern Observatory (ESO) 1998

Online publication: September 8, 1998