SWS observations of solid CO2 in molecular clouds

Th. de Graauw - D.C.B. Whittet - P.A. Gerakines - O.H. Bauer - D.A. Beintema - A.C.A. Boogert - D.R. Boxhoorn - J.E. Chiar - P. Ehrenfreund - H. Feuchtgruber - F.P. Helmich - A.M. Heras - R. Huygen - D.J.M. Kester - D. Kunze - F. Lahuis - K.J. Leech - D. Lutz - P.W. Morris - T. Prusti - P.R. Roelfsema - A. Salama - S.G. Schaeidt - W.A. Schutte - H.W.W. Spoon - A.G.G.M. Tielens - E.A. Valentijn - B. Vandenbusshe - E.F. van Dishoeck - P.R. Wesselius - E. Wieprecht - C.M. Wright

Abstract:

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

Keywords:
ISM: molecules - dust, extinction - Infrared: interstellar: lines - Stars: pre-main sequence - Galaxy: center

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