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Nika2 : mesure de la polarisation avec des KIDs et perspectives pour la mesure du fond diffus cosmologique

Abstract : The polarization is an important probe of many astrophysical and cosmological processes. The study of the Cosmic Microwave Background (CMB) is one of the major goals in Cosmology because it represents an important source of information on the cosmological model of the Universe. The measure of CMB polarization, and in particular the detection of its B modes, would sign the presence of primordial gravitationnal waves and be a powerful probe of inflation. In Astrophysics, the magnetic field can be traced via the observation of dust polarization, and its observation by Planck reveals a well organized magnetic field at large angular scales. Observations have shown that stellar formation takes place in dense filamentary structures and suggest that magnetic field plays an important role in it. High resolution observations of polarization in the filaments will allow us to further probe the role of magnetic field in star formation, and this is one of the main goals of the polarized channel of the NIKA2 camera. Polarization with NIKA2 is reconstructed thanks to the continuous rotation of a Half Wave Plate (HWP) and detectors of a new technology : KIDs (Kinetic Inductance Detectors). It is the only experiment that uses this combination, it thus gives an important feedback in the perspective of deploying it on future CMB polarization instruments.A part of this thesis focuses on the characterization of the polarization module of NIKA2. It presents the data analysis that allows the reconstruction of polarization and the methods that were developed to subtract systematic effects such as the parasitic signal from the HWP and instrumental polarisation.In the context of the search for B modes and in the perspective of doing more precise estimations of polarization, the last part presents two studies : one on the construction of new estimators of polarization that take into account the noise on intensity, and the other one on non-linearity produced by the reconstruction of a KID signal and how it impacts the detection of CMB B modes.
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Aina Andrianasolo. Nika2 : mesure de la polarisation avec des KIDs et perspectives pour la mesure du fond diffus cosmologique. Astrophysique [astro-ph]. Université Grenoble Alpes, 2019. Français. ⟨NNT : 2019GREAY077⟩. ⟨tel-02936622⟩

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