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De l'astrophysique des amas de galaxies à la physique des microcalorimètres en rayons X : performances scientifiques et calibration du X-ray integral field unit de la mission Athena

Abstract : Future breakthroughs in X-ray astronomy require a new generation of X-ray instruments, capable of observing the sky with high spectral and spatial resolutions combined. This need drives the development of the X-ray Integral Field Unit (X-IFU) onboard the future European X-ray observatory Athena scheduled for a launch in 2031. The complexity of the X-IFU and of its readout chain calls for a close monitoring of its instrumental effects. This can be investigated using dedicated end-to-end simulators, which reproduce an X-ray observation, from the emission of X-rays by an astrophysical source to their detection. In the first part of this thesis, I use this approach to quantify the impact of crosstalk between pixels, to derive the requirement on the reproducibility of the instrumental background, and to estimate the line sensitivity of the instrument. I demonstrate that the X-IFU will be capable of observing bright, extended sources with a required high-resolution throughput above 80%. I also show that an accurate knowledge of the spectral lines (their energy and their profile), as well as of the non-X-ray background level (to better than 2%) are needed to minimise systematic errors in the observation. Analysis of the instrumental effects need to be coupled with feasibility studies of the core science objectives of the X-IFU to verify the potential of the instrument. This is valid in particular for extended sources, which will use this integral field unit at its full capabilities. In the second part of this work, I investigate the ability of the X-IFU to characterise the properties of the intra-cluster medium and its turbulent motions. To guarantee a representative result, both toy models and hydrodynamical simulations of clusters are used as inputs of end-to-end simulations. My results underline the strengths of the X-IFU, which will provide an accurate view of the physics and the chemical enrichment of clusters, even at high redshift (z ~ 2) with typical 100ks exposure. I also put forward an analytical way to estimate the systematic errors on line diagnostics in turbulence-related studies, which will be of particular interest to optimise future observations. To fulfil its science objectives, the X-IFU will require a careful calibration. The third part of this thesis presents studies on this topic related to the energy scale, the instrumental background, or the quantum efficiency. I demonstrate that new methods of gain drift correction and background monitoring are required to meet the expected requirements. These results provide constraints on the design of the instrument (e.g., modulated X-ray sources, correction strategies) and can be used to plan ground or in-flight calibration activities. Calibration studies will also be performed experimentally, notably using the test bench developed and characterised at IRAP during my thesis.
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Submitted on : Friday, May 29, 2020 - 3:28:08 PM
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Edoardo Cucchetti. De l'astrophysique des amas de galaxies à la physique des microcalorimètres en rayons X : performances scientifiques et calibration du X-ray integral field unit de la mission Athena. Astrophysique galactique [astro-ph.GA]. Université Paul Sabatier - Toulouse III, 2019. Français. ⟨NNT : 2019TOU30162⟩. ⟨tel-02651013⟩



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