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[43.10] The Evolution of Astrophysical Ices: the Carbon Dioxide Diagnostic

P. A. Gerakines (Astro- & Solar-System Physics Program, Dept. of Physcs, Univ. of Alabama at Birmingham), D. C. B. Whittet, S. Shenoy (Dept. of Physics, Applied Physics, & Astronomy, Rensselaer Polytechnic Institute), E. Bergin (University of Michigan), J. E. Chiar (NASA Ames Research Center), E. L. Gibb (University of Notre Dame)

Using Spitzer Infrared Spectrometer (IRS), we are carrying out a comprehensive study of the carbon dioxide (CO₂) bending-mode absorption feature centered near 15\mum in astrophysical ices. Previous observations with the Infrared Space Observatory, together with studies of laboratory analogs, have shown that this feature has strong diagnostic properties. Notably, substructures within the feature are sensitive to the thermal history of the ices and to the formation of linked CO₂/CH₃OH complexes.

In this Spitzer study, a large range of interstellar environments will be observed, from pristine ices in dark clouds to processed ices in the vicinity of embedded stars. Having such a varied set of sight lines will help to build a clear picture of the evolution of ices from the interstellar medium to protostellar envelopes and protoplanetary disks. Observed spectra will be compared to that of solid CO₂ obtained in the laboratory for interpretation. Here, we describe the motivations and expected results for this study and present our analyses of the solid CO₂ spectra obtained to date.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.