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Gestion de grands catalogues et application de releves infrarouges a l'etude de la structure galactique

Abstract : The first part of this thesis concerns the management of very large astronomical catalogues. Two large projects aiming at covering the sky at near-infrared wavelength were running during this thesis: DENIS and 2MASS. I present the dedicated lossless compression methods, preserving an indexation based on celestial positions, that have been developed for the point source catalogues of these two surveys. Optimized coding leads to compression factors 1.5 to 2 times better than those achieved by LZ77-type algorithms. The first versions of the DENIS and 2MASS catalogues are fully integrated into the CDS services (VizieR, Aladin), and can be queried via the Web, with average response times below 20 microseconds per source. Within the frame of the DENIS project, data validation has allowed the first public release for this survey (\url(http://cdsweb.u-strasbg.fr/denis-public/)). Comparison of data reduced by the two DENIS pipelines (LDAC and PDAC) led to the definition of filtering criteria for selecting PDAC data suitable for Galactic structure studies. The second part of this thesis is based on the use of a modified version of the Besançon synthetic model of stellar population synthesis. The disc density laws have been changed to allow simulation of a warped and/or flaring stellar disc. Comparisons with PDAC data yield a 2.5~kpc scale length for the thin disc, with radial cutoff at 14~kpc. I present a method for reconstructing the 3D structure of extinction by fitting the model on DENIS data. The warp is observed between $l=230$ and 330\degres\xspace, bending the disc towards $b<0$, as in the gas. The warp is found to start close to the Sun ($R=8.4$~kpc), and the radius for the flare depends on the galactic longitude.
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https://tel.archives-ouvertes.fr/tel-00004024
Contributor : Sebastien Derriere <>
Submitted on : Thursday, December 18, 2003 - 5:51:44 PM
Last modification on : Thursday, July 9, 2020 - 3:46:07 PM
Long-term archiving on: : Wednesday, September 12, 2012 - 12:10:10 PM

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  • HAL Id : tel-00004024, version 1

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Sebastien Derriere. Gestion de grands catalogues et application de releves infrarouges a l'etude de la structure galactique. Astrophysique [astro-ph]. Université Louis Pasteur - Strasbourg I, 2001. Français. ⟨tel-00004024⟩

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