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Systèmes Lorentziens Lyman-alpha à grand décalage spectral: Etude de l'hydrogène moléculaire

Abstract : High redshift Damped Lyman-alpha systems, observed in absorption on the line of sight to background quasars, are the spectral signatures of the interstellar medium in the distant Universe. However, few tools are available to understand the physical properties of the associated objects. A technique that relies on well-understood physics and has been widely applied to the local interstellar medium is the study of molecular hydrogen. The specific radiative and collisional properties of this molecule make it a very sensitive probe of the physical conditions in the gas.

In this thesis, I study the presence of molecular hydrogen in the interstellar medium at high redshift, from a unique sample of Damped Lyman-alpha systems observed at high signal-to-noise ratio and high spectral resolution. Subsequent work aim to investigate the properties of and physical conditions in the neutral gas associated to these systems (temperature, density, chemical composition, molecular fraction, dust content, intensity of the radiation field).

In parallel, I perform a systematic search for and a statistical study of Damped Lyman-alpha
systems in order to measure the neutral gas content of the Universe, characterize its distribution and its evolution with cosmic time and therefore constrain galaxy formation.

Finally, I show the possibility of detecting and studying other molecules like deuterated molecular hydrogen and carbon monoxide in the interstellar medium at high redshift. The tools developed in this thesis for automatic analysis of spectra lead to the first detection of CO in such a medium, opening the way to interstellar astrochemistry in the distant Universe.
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Contributor : Pasquier Noterdaeme <>
Submitted on : Thursday, September 10, 2009 - 8:42:06 AM
Last modification on : Tuesday, December 8, 2020 - 3:38:46 AM
Long-term archiving on: : Tuesday, June 15, 2010 - 11:24:44 PM


  • HAL Id : tel-00414784, version 1


Pasquier Noterdaeme. Systèmes Lorentziens Lyman-alpha à grand décalage spectral: Etude de l'hydrogène moléculaire. Astrophysique [astro-ph]. Université Pierre et Marie Curie - Paris VI, 2008. Français. ⟨tel-00414784⟩



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