SWS observations of solid CO_2_ in molecular clouds.
Lutz, D.; Heras, A. M.; Prusti, T.; Beintema, D. A.; de Graauw, T.; Feuchtgruber, H.; Morris, P. W.; van Dishoeck, E. F.; Salama, A.; Whittet, D. C. B.; Schutte, W. A.; Tielens, A. G. G. M.; Boogert, A. C. A.; Ehrenfreund, P.; Gerakines, P. A.; Helmich, F. P.; Wright, C. M.; Roelfsema, P. R.; Kunze, D.; Lahuis, F.; Bauer, O. H.; Boxhoorn, D. R.; Huygen, R.; Kester, D. J. M.; Schaeidt, S. G.; Valentijn, E. A.; Wesselius, P. R.; Wieprecht, E.; Spoon, H. W. W.; Leech, K. J.; Chiar, J. E.; Vandenbusshe, B.
Abstract
We report absorption features of solid CO_2_ stretching and bending modes in several lines of sight, including embedded young stellar objects and the Galactic Center source Sgr A*. The overall CO_2_ abundance in ices is ~15% relative to H_2_O. Profile shapes are consistent with the presence of grain mantles with distinct polar (H_2_O-rich) and nonpolar (CO or CO_2_-rich) layers. In addition to the normal isotopic form, we report detection of the stretching mode of ^13^CO_2_; the ^12^C/^13^C ratio is consistent with terrestrial and interstellar values.