Le mercredi 18 juin 2025, Sandrine JUILLARD présentera l'examen en vue de l’obtention du grade académique de Docteur en Sciences (Collège de doctorat en Sciences spatiales) sous la direction de Olivier ABSIL et Valentin CHRISTIAENS.

Cette épreuve consistera en la défense publique d’une dissertation intitulée :

« Robust post-processing algorithms for near-infrared high-contrast imaging of protoplanetary disks ».

Le Jury sera composé de :

M. M. FAYS (Président), Mme et MM. O. ABSIL (Promoteur), F. CANTALLOUBE (Université Grenoble Alpes), V. CHRISTIAENS (Co-promoteur) (Secrétaire), C. GINSKI (University of GALWAY), G. LOUPPE, J. MILLI (Université Grenoble Alpes).

Abstract

Disk interactions in protoplanetary disks can significantly reshape the disk and influence the planet formation process. Studying these interactions is therefore crucial to better understand the formation and evolution of planetary systems. In high-contrast imaging (HCI), after most of the starlight and aberrations caused by atmospheric turbulence have been removed by the coronagraph and adaptive optics, residual atmospheric speckles and quasi-static speckles—unseen by the adaptive optics system or stemming from imperfections of the optics system itself—remain on the science images. These speckles (referred to as PSF) must be removed to reveal the faint circumstellar signal hidden in the vicinity of the star. PSF modeling and subtraction is a particularly challenging step in data post-processing. Distinguishing real astrophysical signals from artifacts, and separating point sources from filtered extended structures, remains difficult. Understanding the limitations of HCI post-processing is essential for reliably interpreting disk morphologies and identifying planet candidates. This PhD project aims to analyze, compare, and develop new methods to improve the robustness of disk imaging.

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