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Etude de la matière interstellaire : Caractérisation de l'émission des grains

Abstract : My work is focused on the understanding of the interstellar dust emission properties in the submillimeter wavelength range and on the coupling between dust and gas in dense and cold interstellar regions. Some remarkable astrophysical observations (PRONAOS, FIRAS) revealed that interstellar dust has unusual emission properties at long wavelength. These properties cannot be understood with the standard model of dust grains. To explain these unusual emission properties we proposed a model based on the intrinsic properties of amorphous grains. Our model is able to explain simultaneously the anticorrelation between temperature and spectral index observed by PRONAOS (Dupac et al. 2003) and the millimetre excess observed by FIRAS. This model will define the basis of a new model of dust grains. To have a better understanding of emission and absorption properties of interstellar dust, I also performed laboratory experiments on absorption properties of different kinds of amorphous silicates, at low temperature and long wavelength. For the first time, we distinguished two different spectral behaviour (500Μm-1mm) and (200Μm-100Μm) of the absorption coefficient. For wavelengths between 500Μm and 1mm, we found a significant anticorrelation between the spectral index and the temperature similar to the one observed by PRONAOS. This behaviour could be related to the presence of defects modifying the structure (OH groups or Mg2+ ions). In the cold and dense regions, dust emission properties are modified, for instance by grain agglomeration processes which are favorised by the presence of ice onto dust grains. In this research context, we have studied the relationship between the modification of dust emission properties and gas properties. The study of molecular species N2H+ and CO in the direction of a Taurus filament, with the IRAM telescope, proved that agglomeration processes were not initiated by the existence of CO ice on grains but more certainly by the presence of H20 ice. We confirmed SWAS results on the lack of water in gas phase in the cold and dense regions studying a dark cloud Cha-MMS1 by its submillimeter water emission in this fundamental transition with ODIN satellite.
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https://tel.archives-ouvertes.fr/tel-00009589
Contributor : Nathalie Boudet <>
Submitted on : Friday, June 24, 2005 - 12:01:11 PM
Last modification on : Thursday, October 15, 2020 - 4:07:07 AM
Long-term archiving on: : Friday, April 2, 2010 - 10:30:49 PM

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Nathalie Boudet. Etude de la matière interstellaire : Caractérisation de l'émission des grains. Astrophysique [astro-ph]. Université Paul Sabatier - Toulouse III, 2005. Français. ⟨tel-00009589⟩

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