# Le milieu interstellaire et le cycle des grains dans le Petit Nuage de Magellan

Abstract : This thesis is dedicated to the depiction of interstellar medium (ISM) in the Small Magellanic Cloud (SMC). This galaxy, a nearby template of galaxies at their early stages, has a low metallicity and a high star formation rate.

This work focuses on dust properties from the diffuse medium to star forming regions in the SMC. Analysis and modelling of the infrared emission in these environments show that (1) the grains are globally destroyed in the diffuse medium; (2) PAHs destruction could not be a systematic characteristic of low metallicity ISM.

A second part aims at studying the millimeter dust emission as a molecular gas tracer in dense clouds. Its comparison with CO observations, points towards a linear evolution of the CO-to-H$_2$ conversion factor with metallicity. Masses obtained from this tracer for the local molecular clouds agree with those obtained from CO observations. For the molecular clouds of the SMC, a systematic excess is observed with respect to virial masses. It can be explained by an additionnal support of the cloud by magnetic fields.

Jointly, these studies show an evolution of the gas-to-dust ratio in the SMC. In the diffuse medium, grains are destroyed by the numerous supernovae explosions. Heavy elements reaccrete on dust in the denser regions.

These studies stand as scientific cases of the Virtual Observatory (VO) use. In this context, a data base on the Magellanic Clouds was build, which is a prototype of team's data bases in the VO. Furthermore, describing the processing and analysis steps allows the statement of necessary developments for the inclusion of extended objects in the VO and generic tools were proposed.
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Cited literature [57 references]

https://tel.archives-ouvertes.fr/tel-00152441
Contributor : Caroline Bot <>
Submitted on : Wednesday, June 6, 2007 - 6:12:50 PM
Last modification on : Friday, October 23, 2020 - 4:52:17 PM
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### Identifiers

• HAL Id : tel-00152441, version 1

### Citation

Caroline Bot. Le milieu interstellaire et le cycle des grains dans le Petit Nuage de Magellan. Astrophysique [astro-ph]. Université Louis Pasteur - Strasbourg I, 2005. Français. ⟨tel-00152441⟩

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