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Développement de nouveaux outils de traitement et d'analyse pour l'Optique Adaptative Grand Champ

Abstract : The next decade will see the first light of the new Extremely Large Telescopes (ELTs). Those giant telescopes with an aperture for its primary mirror from 25 meters up to 40 meters across, will address fundamental questions of modern astrophysics from exoplanet direct imaging to the study of the first galaxies. Their large diameter, increases both their sensitivity and their angular resolution, which is the ability to discern the very small details. However, the angular resolution of all sizes ground-based telescope is always strongly limited by the atmospheric turbulence. These movements of air layers with different temperatures induce fluctuation in the optical index and alter the shape of the incident wavefront. To tackle this problem and fully exploit their capabilities, large optical telescopes had become indissociable of their Adaptive Optics (AO) instruments. AO is a technic that consists in analyzing the effects of turbulence on the wavefront and compensating for it in real time, thanks to one or several deformable mirrors in order to restore the initial angular resolution of optical telescopes. In addition, most of the 8-10 meters telescopes are supplied with laser guide stars systems in order to increase the portion of the sky that can benefit for such an AO correction. Lately, a Wide Field AO system has been implemented on the 8 meters Gemini South telescope: the Gemini Multi-Conjugated AO (GeMS) instrument. With its five laser guides stars, it corrects turbulence at different altitudes and provides AO corrected images over much larger a field of view than regular AO. In a first part of this PhD, I collected data with the GeMS instrument in order to study the formation of massive stars in a young cluster. Such science cases should largely benefit from the new performance offered by Wide field AO at near infrared wavelengths. Thanks to these observations, we detected a large number of very young stellar objects, as well as several massive stars. We also developed a possible triggered formation scenario for the stellar population in this region. In addition to new science results, the study carried out on these observations has enable to highlight the critical parameters that limit the scientific analyses of Wide Field AO data. Indeed, despite the excellent performance of such systems, the correction performed is not perfect and some residuals still limit the image quality. In order to get the best science results out of the Wide Field AO images, dedicated and optimized reduction and analyses tools are needed. In this context, I paid a particular attention to variable distortion observed on Wide Field AO data, which was identified as a limiting factor which affects astrometry and photometry studies. I present in this document a new and original method of distortion correction based on an inverse problem approach. I detail the formalism as well as the whole validation steps, from the characterization on simulated data to the application on real data. While this last application is specifically valid for GeMS data, the proposed method remains relevant to correct distortion in any image affected by this phenomenon, and especially in science observations from the future ELTs.
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https://tel.archives-ouvertes.fr/tel-01702439
Contributor : Anaïs Bernard <>
Submitted on : Tuesday, February 6, 2018 - 5:57:30 PM
Last modification on : Friday, June 26, 2020 - 2:28:05 PM
Long-term archiving on: : Tuesday, May 8, 2018 - 6:29:48 AM

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  • HAL Id : tel-01702439, version 1

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Anaïs Bernard. Développement de nouveaux outils de traitement et d'analyse pour l'Optique Adaptative Grand Champ. Instrumentation et méthodes pour l'astrophysique [astro-ph.IM]. Aix-Marseille Université, 2017. Français. ⟨tel-01702439⟩

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