Poster title: ALMA and SPHERE/IRDIS 3D modeling of HD 163296

Poster abstract: Protoplanetary disks are the sites of planet formation. As such the study of these is of great importance 
to understand the planet formation process and planet-disk interactions that lead to the wide variety of planetary systems 
we observe in terms of planetary masses, location and composition. 
Protoplanetary disks can be observed in a broad wavelength range, ranging from the optical to millimeter wavelengths. 
While optical and infrared observations reveal the small dust grains on the surface of the disks, the larger dust grains in 
their interiors can be probed at longer wavelengths. Multi-wavelength observations are thus indispensable in studying disk 
geometry and dust evolution processes, both of which are key to understanding the planet formation process.
We aimed to construct a 3-dimensional model of HD 163296 capable of reproducing simultaneously new observations of 
the disk surface in polarized scattered light with the SPHERE/IRDIS instrument and thermal emission continuum 
observations of the disk midplane with ALMA. We want to determine why the SED of HD 163296 is intermediary between 
the otherwise well-separated group I and group II Herbig stars.
The disk was modeled using the Monte Carlo radiative transfer code MCMax3D. The radial dust surface density profile 
was modeled after the ALMA observations, while the polarized scattered light observations were used to constrain the 
inclination of the inner disk component and turbulence and grain growth in the outer disk.
While three rings are observed in the disk midplane with ALMA at ~80, 124 and 200 AU, only the innermost of these is 
observed in polarized scattered light, indicating a lack of small dust grains on the surface of the outer disk. We provide 
two models capable of explaining this difference by two separate mechanisms: increased settling to bring the small dust 
grains on the surface of the outer disk closer to the midplane, and a depletion of the smallest dust grains in the outer disk 
to decrease the optical depth at optical and NIR wavelengths in this zone. In the region outside the fragmentation-
dominated regime, such depletion is expected from state-of-the-art dust evolution models. We also studied the effect of 
creating an artificial inner cavity in our models, and conclude that HD 163296 might be a precursor to typical group I 
sources.