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Analyse des propriétés statistiques des amas de galaxies

Abstract : Clusters of galaxies are one of the major tools of modern cosmology. A measure of the abundance of these objects can be used to characterize the cosmological properties of the Universe and the analysis of their different physical properties such as mass, temperature or the X-ray luminosity of the intracluster gas can constrain models of formation and evolution of these objects. In both cases, the fundamental quantity is the mass of the galaxy cluster. Being able to estimate them in the most efficient and accurate possible way is then mandatory. The work presented here is part of this: the study of a representative sample of galaxy clusters with masses deduced from two completely different methods in order to increase their reliability. This thesis focuses on the method that uses the gravitational lensing effects predicted by the theory of General Relativity. The analysis of wide field optical images of clusters formed the bulk of this work: selection of lensed galaxies, estimate their shape, measure of the shear signal and reconstruction of the mass. Each step is accompanied by errors and limitations that were highlighted, particularly those attributed to the large distance of the sample of clusters. Its study in terms of statistics was used to characterize the so-called scaling laws. These relationships between the different properties of clusters are used to study models of structures formation and provide the necessary tool to use clusters as a cosmological constraint. Their calibration therefore requires a robust estimate of the masses. Those deduced from the analysis of the effects of gravitational lenses have been compared with the results of the second method based on the X-ray emission of the intracluster gas. For 7 of the 11 clusters in the sample, the estimated masses are consistent which increases their credibility. For other cases, the differences highlight the limitations inherent to each method, especially projection effects and the dynamical state of the cluster. The results obtained on the calibration of the scaling laws are in good agreement with several other works of the same type, especially with nearby clusters. In particular, the presence of non-gravitational physical processes is highlighted, both on the gas properties and those of the population of cluster galaxies.
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Submitted on : Thursday, September 29, 2011 - 3:56:47 PM
Last modification on : Monday, July 4, 2022 - 9:52:52 AM
Long-term archiving on: : Friday, December 30, 2011 - 2:31:26 AM


  • HAL Id : tel-00627801, version 1


Gaël Foëx. Analyse des propriétés statistiques des amas de galaxies. Astrophysique [astro-ph]. Université Paul Sabatier - Toulouse III, 2011. Français. ⟨tel-00627801⟩



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