Evolution of the radial and vertical distribution of protoplanetary disks from scattered-light observations

Protoplanetary disks are the sites of planet formation. They are mainly composed by molecular gas, however, accessing the gas distribution from observations (including gas mass and its radial/vertical extension) in disks is challenging. Therefore, most of the information that we have about planets forming in disks comes from the dust that dominates the disk opacity.

Observationally, we can access the distribution of micron-sized particles and pebbles (mm/cm-sized particles) trough observations of scattered-light at optical/near infrared and interferometric (sub-) millimeter observations, respectively. Due to the aerodynamical drag from the gas, pebbles are subject to radial drift and settling to the midplane in disks.

For this reason, the radial and vertical extension of pebbles inferred from observations do not trace the actual gas disk distribution.

However, small grains are expected to be well coupled to the gas and their distribution is close to the gas distribution. Recently, the SPHERE instrument at VLT have provided unprecedented scattered-light images of several protoplanetary disks. This PhD project aims to connect models of gas and dust evolution in protoplanetary disks under different physical conditions that can rule their evolution and compare the results with state-of-the-art SPHERE observations.

I am part of an international collaboration of a large accepted program (DESTINYS), which targets 85 protoplanetary disks around T-Tauri stars in different star forming regions with different age (from ~1 to 10 million years). With the privileged access to these data, in this project we will investigate the radial and vertical distribution in protoplanetary disks as seen in scattered light and its evolution, connect to what is observed at mm-emission from powerful telescopes, such as ALMA, in order to have a better understanding of the physical mechanisms that rule the evolution of disks.

There are two leading mechanisms proposed for transporting mass and angular momentum that drive global disk evolution: turbulent viscosity and Magneto-hydrodynamical (MHD) disk winds, both of them leave different imprints on the evolution of the gas disk size: while the disk is expected to expand with time in the turbulent viscosity case, the opposite happens in the case of MHD winds. On the other hand, the vertical distribution of the small grains in protoplanetary disks can provide constrains on the vertical turbulence in the disks , and with this project we will study the potential evolution of such vertical turbulence.

The knowledge of what drives the evolution of protoplanetary disk is a key element to understand how planets form in these systems and to link with the large population of exoplanets observed up to day.