Physics
Scientific paper
Nov 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000esasp.456...71d&link_type=abstract
ISO beyond the peaks: The 2nd ISO workshop on analytical spectroscopy. Eds. A. Salama, M.F.Kessler, K. Leech & B. Schulz. ESA-SP
Physics
1
Iso, Ice, Spectroscopy, Ysos
Scientific paper
With its large spectral coverage and resolution, well adapted to the study of solid state features arising from icy interstellar grain mantles present in dense molecular clouds, the SWS instrument on board ISO can be used to probe the molecular material in the lines of sight to bright infrared protostellar sources. An example is presented here with the observations of the protostellar object RAFGL 7009S. However, the results presented are applicable to numerous extinct massive young stellar objects which behave similarly. Deep solid state features are detected in such extinguished sources. These features can be compared with laboratory data which allow the identification of ice mixtures composed of H2O, CH4, CO, CO2 and CH3OH condensed on top of refractory grains. Quantitative estimates of the abundances of these molecules can therefore be derived. Superimposed on these solid state features, one generally observe the ro-vibrational lines of gas phase species such as H2O, CO, CO2 and CH4. Analysis of these lines helps to derive some physical parameters such as the gas temperature and the gas-to-solid ratios for these molecules. In the RAFGL 7009S source, an upper limit on the deuterium/hydrogen ratio can also be placed and the consequences for the high fractionation observed in the gas can be discussed. The analysis of the profile of the solid carbon dioxide ν2 bending mode reveals particular interactions in the ice mantles. Indeed, through the peculiar substructure observed in the CO2 band we can monitor in such sources the formation of a complex involving the CO2 and CH3OH and the temperature evolution of the ices. These results may shed light on the relationship between the gas and the grains with possible implication for interstellar chemistry around these objects. Careful laboratory experiments involving matrix isolation techniques allow us to describe the physical nature of the observed ices as well as their photochemical evolution.
d'Hendecourt Louis
Dartois Emmanuel
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