Anton Pannekoek Institute for Astronomy

PhD defense Tomas Stolker - protoplanetary disks and exoplanets in scattered light

30 August 2017

On September 7, 2017, Tomas Stolker will defend his PhD thesis "Protoplanetary disks and exoplanets in scattered light".


High-contrast imaging facilitates the direct detection of protoplanetary disks in scattered light and self-luminous exoplanets on long-period orbits. The combined power of extreme adaptive optics and differential imaging techniques delivers high spatial resolution images of disk morphologies down to several astronomical units from the star. The distribution of the small dust grains in the disk surface provides important clues about the processes that drive disk evolution and the shaping effects of embedded planets on their circumstellar environment. The scattered light is also imprinted by the properties of the dust particles through their color and angle of scattering.

In this thesis, a new scattering radiative transfer code for exoplanet atmospheres is presented which is used to predict the polarization signal from young gas giants with atmospheric cloud variations and circumplanetary disks. Furthermore, four protoplanetary disks are studied in scattered light with the SPHERE instrument at the Very Large Telescope. Intriguing substructures and brightness asymmetries are revealed in all disks including shadows, spiral arms, gaps and cavities. The structure and dynamics of the innermost disk regions are investigated with shadows that are cast on the outer disk while the detected spiral arms, gaps and cavities are used as tracers for embedded planets. The disk structure and dust properties are quantified with three-dimensional radiative transfer simulations. Additionally, a numerical method is developed that allows for a more precise determination of the scattering phase function of the dust by considering the geometry of the disk surface.

Published by  Anton Pannekoek Institute for Astronomy