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Extending the realm of galaxies to the low surface brightness universe

Abstract : The exploration of diffuse light emission and the outskirts of galaxies in the regime of the Low Surface Brightness (LSB) is of utmost importance to understand the formation mechanism of galaxy evolution, and is essential to constrain the current theoretical models and numerical simulations in the cosmological context. Observational data, both in optical and radio emission, complemented with hydrodynamical cosmological numerical simulations provide us a crucial information about the morphological properties of substructures surrounding massive galaxies, as well as the mass distribution, molecular gas content and star formation of LSB galaxies such as the recently discovered Ultra Diffuse Galaxies (UDGs).This thesis presents several analysis addressed to the study of these schemes. In first instance, motivated in the most recent works about optimized deep imaging surveys observed with the CFHT telescope, which have revealed prominent LSB fine structures classified like tidal tails, stellar streams and shells, we have computed statistics of an hydrodynamical numerical simulation in order to interpret observations and make inferences about the past mass assembly of galaxies. We made a census of these substructures and computed their survival time. We also studied their dependence with several properties like the projection and the surface brightness. We found that shells and streams remains visible around 4 Gyr and they are mainly associated to minor mergers and a continuous diffuse gas accretion, while tidal tails have a durability time of around 1 Gyr and are correlated with major merger events. In parallel, in this work we made use of a semi-empirical approach to build-up a mock catalog with the aim to make predictions about scaling relations and constrain physical parameters of UDGs and LSB galaxies.On the other hand, we have performed CO spectroscopy surveys of UDGs observed at IRAM-30m to quantify the molecular gas content. The selected galaxies were conformed by sources from several environments and different properties, including objects like the very red galaxies Dragonfly 44 and DGSAT I. We have obtained unprecedented upper limits of their CO mass (few 10^6 - 10^7 solar masses). We also made CO observations at IRAM-30m to detect molecular gas content in a sample of four early-type galaxies that exhibit prominent shell galaxies like the case of NGC 0474 and Arp 230. Our goal is to test the phase wrapping formation model proposed in numerical simulations. We detected a molecular mass of around 10^8 solar masses in several shells of one galaxy of our sample and we report the mass upper limits for the other cases.
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Submitted on : Tuesday, June 30, 2020 - 11:51:18 AM
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Brisa Mancillas Vaquera. Extending the realm of galaxies to the low surface brightness universe. Astrophysics [astro-ph]. Université Paris sciences et lettres, 2019. English. ⟨NNT : 2019PSLEO013⟩. ⟨tel-02884959⟩



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