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Astron. Astrophys. 315, L345-L348 (1996)

SWS observations of solid CO2 in molecular clouds*

Th. de Graauw1,2, D.C.B. Whittet3, P.A. Gerakines3, O.H. Bauer4, D.A. Beintema1,5, A.C.A. Boogert2, D.R. Boxhoorn1, J.E. Chiar3, P. Ehrenfreund6, H. Feuchtgruber4,5, F.P. Helmich6, A.M. Heras5, R. Huygen7, D.J.M. Kester1, D. Kunze4, F. Lahuis5, K.J. Leech5, D. Lutz4, P.W. Morris5,8, T. Prusti5, P.R. Roelfsema1,5, A. Salama5, S.G. Schaeidt4,5, W.A. Schutte6, H.W.W. Spoon8, A.G.G.M. Tielens9, E.A. Valentijn1, B. Vandenbusshe5,7, E.F. van Dishoeck6, P.R. Wesselius1, E. Wieprecht4,5, and C.M. Wright4

1 SRON, P.O. Box 800, 9700 AV Groningen, The Netherlands
2 Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
3 Department of Physics, Applied Physics & Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
4 Max-Planck-Institut für Extraterrestrische Physik, Postfach 1603, D-85740 Garching, Germany
5 ISO Science Operations Centre, Astrophysics Division, ESA, Villafranca del Castillo, P.O. Box 50727, E-28080 Madrid, Spain
6 Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands
7 Sterrenkundig Instituut, K.U. Leuven, Celestijnenlaan 200B, B-3001 Heverlee, Belgium
8 SRON, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
9 NASA Ames Research Center, Mail Stop 245-6, Moffett Field, CA 94035, USA

Received 1 July 1996 / Accepted 29 August 1996

Abstract. We report absorption features of solid CO2 stretching and bending modes in several lines of sight, including embedded young stellar objects and the Galactic Center source Sgr A*. The overall CO2 abundance in ices is img3.gif 15% relative to img4.gif . Profile shapes are consistent with the presence of grain mantles with distinct polar ( img4.gif -rich) and nonpolar (CO or CO2-rich) layers. In addition to the normal isotopic form, we report detection of the stretching mode of 13CO2; the 12C/13C ratio is consistent with terrestrial and interstellar values.

Key words: ISM: molecules - dust, extinction - infrared: interstellar: lines - stars: pre-main sequence - Galaxy: center

* 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.

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Last change: December 16, 1996
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