1. The evolution of very small dust particles in molecular clouds observed with ISOCAM
- Author
-
M. M. Casali, P. Persi, Francois Boulanger, Jean-Loup Puget, Pascal André, Alain Abergel, Michel Perault, C. J. Cesarsky, J. P. Bernard, L. Nordh, Thierry Montmerle, A. A. Kaas, D. Cesarsky, M. Huldtgren, Marc-Antoine Miville-Deschenes, Sylvain Bontemps, F. Sibille, Edith Falgarone, G. Olofsson, and Anthony P. Jones
- Subjects
Physics ,Infrared ,Spatial structure ,Molecular cloud ,Dust particles ,General Engineering ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Radiation ,Wavelength ,Space and Planetary Science ,Low density ,Small particles - Abstract
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.
- Published
- 2002