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Détermination des paramètres cosmologiques à l'aide des supernovae de type Ia à grands décalages vers le rouge

Abstract : This thesis was done within the context of the international collaboration SuperNova Legacy Survey, SNLS. The main goal of this project is to measure precisely the cosmological parameters and to study the characteristics of dark energy, via its equation of state. To this end, a broad sample of SNe Ia at large redshifts is collected using MegaCam, a camera installed on the 3.6 meters telescope CFH, located in Hawaii. Several hundred SNe Ia, with redshifts ranging between 0.3 and 1, will be measured during the five years planned for the project. We first show how the type Ia SNe can be used as standard candles, objects whose luminosity is reproducible, in order to make distance measurements in cosmology. We then present the various steps going from the raw image provided by the telescope to the discovery of the supernova, and then the determination of its magnitude using a standard star catalogue. The photometric follow-up of the SNe, in order to build their light curves, and the search for new candidates are done in a simultaneous way by repetitive observations of the same fields. A light curve model was elaborated in order to estimate the rest-frame flux of the supernova, for a broad range of wavelengths. Parameters derived from the light curves fit (maximum luminosity, decline rate, color) are used to build a distance estimator. The distance comparison between nearby SNe, taken from the literature, and distant SNe, observed with SNLS, makes it possible to determine the cosmological parameters. The results obtained confirm the presence of dark energy, which seems to behave as a cosmological constant.
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Contributor : Delphine Guide <>
Submitted on : Wednesday, November 9, 2005 - 4:07:25 PM
Last modification on : Wednesday, December 9, 2020 - 3:11:27 PM
Long-term archiving on: : Friday, April 2, 2010 - 11:06:25 PM


  • HAL Id : tel-00010942, version 1


Delphine Guide. Détermination des paramètres cosmologiques à l'aide des supernovae de type Ia à grands décalages vers le rouge. Cosmologie et astrophysique extra-galactique [astro-ph.CO]. Université Pierre et Marie Curie - Paris VI, 2005. Français. ⟨tel-00010942⟩



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