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Theses

Formation stellaire intergalactique

Abstract : The work presented here is about star formation in the unusual environment of collisional debris studied for the first time as such. These peculiar regions have an interstellar medium, and in particular a metallicity, similar to that of star forming regions in galactic discs while not undergoing similar environment effects such as density waves in the spiral arms for instance.

This study has been conducted with a selection of exceptional systems that have ejected large quantities of gas into the intergalactic medium while also showing some intergalactic star forming regions. Principal Investigator as well as archive spectroscopy and imaging from multi-wavelength observations ranging from far ultraviolet to mid-infrared have been used. Withal a model has been built in order to reproduce the spectral energy distributions of intergalactic star forming regions and constrain the star formation histories, their extinctions and their fraction of stars coming from the parent galaxies' discs. Comparisons have been performed on the estimation of star formation rates between infrared, Halpha and ultraviolet wavelengths.

This thesis has brought the following main new results:
* some regions seem to be deprived of any old stellar population, and these are ideal laboratories in which to study star formation ;
* the mid-infrared star formation rate estimator is as reliable as it is in spiral galaxies ;
* the scatter in the estimation of star formation rates in various bands is similar to that of spiral galaxies and is mainly due to age effects ;
* the combination of the extinction uncorrected Halpha line with mid-infrared yields a good estimation of the actual star formation rate ;
* an important part of star formation, which can be as high as 85%, takes place in the intergalactic medium showing that in a young universe, in which this type of system is much more common than in the nearby universe, star formation from collisional debris can be an important factor of enrichment of the intergalactic medium.
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https://tel.archives-ouvertes.fr/tel-00198707
Contributor : Médéric Boquien <>
Submitted on : Monday, December 17, 2007 - 5:43:38 PM
Last modification on : Friday, April 10, 2020 - 5:10:02 PM
Long-term archiving on: : Friday, November 25, 2016 - 8:25:20 PM

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  • HAL Id : tel-00198707, version 1

Citation

Médéric Boquien. Formation stellaire intergalactique. Astrophysique [astro-ph]. Université Paris-Diderot - Paris VII, 2007. Français. ⟨tel-00198707⟩

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