Resolved spectroscopy of debris disks with SPHERE/VLT

Debris disks are characterized by the dusty, gas-depleted environment bearing non-primordial dust grains which are constantly generated by continuous collisions between planetesimals. High-contrast imaging in the near-infrared allows to measure the intensity distribution of the disk, which is dependent on the properties of these grains. My goal was
to study the scattered light images of debris disks obtained by the SPHERE/VLT instrument installed in Chile. Post-processing techniques used to reduce the stellar contribution in images, such as angular differential imaging, involves self-subtraction of the disk image which must be corrected for to recover true photometry. For this, I use a model of radiative transfer, GRaTer, to model the morphology of the disk and so calculate the effect of self-subtraction. I studied the morphologies and the spatial distribution of the grains of three discs of debris, HD 32297, HD 141569 and HD 106906 and developed models reproducing the density and intensity distribution of these systems. By analyzing the average reflectances and the spectra obtained in modeling the grain size distribution, we see that these disks contain grains smaller than the blowout limit. This result can be attributed to the presence of gas and/or an effect of a collisional avalanche. This study puts a constraint on our current understanding of the evolution of grains towards the planets.