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Theses

Du HI radio à la mesure de la croissance des bassins gravitationnels

Abstract : Motions of galaxies in the universe are due to the rivalry between the expansion of the universe and gravitation. This tug-of-war impacts the formation and the growth of large scale structures of the universe. Thus, depending on the identity of the winner of this duel, the universe is more or less compact. Within this context, this PhD thesis is divided into three parts, spanning from HI observations to the estimate of the growth of rate of large scale structures of the universe and the compactness of the local universe.The Cosmicflows collaboration assembles catalogues of galaxy distances. Up to now, three catalogues have been published, the last one being Cosmicflows-3. This thesis presents and analyses observational data obtained from HI observations. These new data will be used to construct the new compilation of distances Cosmicflows-4 by the use of the Tully-Fisher relation, in order to correct the lack of data in the Northern celestial hemisphere in the current catalog.From the distance of a galaxy, one can derive the radial part of its peculiar velocity corresponding to the component of its total velocity caused by gravitation. Peculiar velocities allow to probe the matter content of the universe and to extract information on large scale structures of the universe. Two methodologies using peculiar velocities have been developed during this thesis to characterize large scale structures of the local universe.On the one hand, peculiar velocity catalogues can be used to reconstruct tri-dimensional velocity fields. These velocity field allow one to map the structure of the local universe and are used in this thesis to identify gravitational basins and valleys within the local universe by computing streamlines.On the other hand, a method based on the analysis of two-point galaxy peculiar velocity correlations has been developed in order to constrain the growth rate of large scale structures of the local universe from observational data. This method is applied to the Cosmicflows-3 catalogue of observed peculiar velocities
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Alexandra Dupuy. Du HI radio à la mesure de la croissance des bassins gravitationnels. Astrophysique [astro-ph]. Université de Lyon, 2018. Français. ⟨NNT : 2018LYSE1201⟩. ⟨tel-02108079v2⟩

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