EAS Publications Series
Volume 4, 2002Infrared and Submillimeter Space Astronomy: An International Colloquium to Honor the Memory of Guy Serra
|Page(s)||79 - 79|
|Section||Session I: Dust and Gas Properties|
|Published online||25 September 2002|
M. Giard, J.P. Bernard, A. Klotz and I. Ristorcelli (eds)
EAS Publications Series, 4 (2002) 79
The evolution of very small dust particles in molecular clouds observed with ISOCAM
Institut d'Astrophysique Spatiale, UMR-8617, Université Paris-Sud, Bât. 121, 91405 Orsay, France
2 Stockholm Observatory, 133 36 Saltsjöbaden, Sweden
3 Radioastronomie Millimétrique, ENS, 24 rue Lhomond, 75005 Paris, France
4 Service d'Astrophysique, Centre d'Études de Saclay, 91191 Gif-sur-Yvette Cedex, France
5 Istituto Astrofisica Spaziale, CNR, Area di Ricerca Tor Vergata, Roma, Italy
6 Observatoire de Bordeaux, BP. 89, 33270 Floirac, France
7 Observatoire de Lyon, France
8 Royal Observatory, Blackford Hill, Edinburgh, UK
We present ISOCAM observations (5-18 μm) of illuminated surfaces of molecular clouds. The emission properties of the transiently heated small particles, which dominate the emission observed by ISOCAM, are analysed in relation with the spatial structure of the material. Striking spatial variations of the infrared colour (5-8.5 μm/12-18 μm) are detected. Spectroscopic observations show that they are due to variations of the intensity of the aromatic features (especially at 7.7 μm) relatively to the continuum emission increasing towards long wavelengths. Compared to the intensity of the continuum emission, the intensity of the aromatic features are significantly fainter at the illuminated surfaces of dense structures than in low density regions surrounding these dense structures. This effect could be the signature of photo-chemical evolution, size segregation due to grain dynamics in uni-directional radiation fields, or abundance variations of very small particles.
© EAS, EDP Sciences, 2002
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