Dynamical and thermal evolution of gas and dust in protoplanetary disks

• Applicant: Dr. Mario Flock
• Subject Area: Astrophysics and Astronomy
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495235860

How, where and when do planets form? These are questions for which scientist are seeking answers since centuries. Today we know that planets form in young circumstellar disks as part of the star formation processes. In this also called proto-planetary disk we have to investigate the evolution of the gas and dust to seek the answers of planet formation. With the help of state-of-the-art theoretical models and advanced observations, we have learned much more about the physical processes, which control the evolution of the gas and dust in protoplanetary disk. Micron-size dust grains determine the heating and cooling processes in the disk by absorbing the stellar radiation in the optical and re-emitting at infrared wavelengths. The resulting temperature structure determines the gas pressure scale height and so shapes the gas density profile. In turn, the density structure affects the motion of the dust grains, how fast they settle and where they get concentrated. The most-promising sites of planet formation are local pressure maxima, which can occur at different locations in the disk. The concept is very simple: dust grains drift to the region of largest pressure, whereas the drift speed is given by their size. Inside local pressure maxima dust grains get concentrated, fostering the growth to larger-sized planetesimals. The evolution of the gas density and temperature structure in protoplanetary disks is a crucial key to understand where dust grains get concentrated and where they can grow to the building blocks of planets. With this project we propose to develop cutting edge theoretical models which open a new pathway in our understanding of the structure formation and thermal evolution. Using radiation hydrodynamical simulations of gas and dust, including for the first time the dust opacity linked to the dust motion, we will be able to capture the most important physics to determine the disk evolution. The special focus lies in the study of the thermal wave instability (TWI), an instability which is caused by the irradiation at the disk surface, and the hydrodynamical response due to changes of the disk scale height. The ability of the TWI to perturb the density and temperature of the disk, leading to pressure variation is of highest interest as these variations promote dust concentration and growth. By further combining the results with dust evolution methods we will learn to which sizes the dust can grow. Finally our dataset will allow us to produce synthetic observations in a richness which was never reached before. Recent multi-wavelength observations show distinct rings and gaps in their emission profiles. Could the TWI be responsible for the rings and gaps? What is the strength of the pressure perturbations caused by the TWI? How is the migration of dust grains and proto-planets affected by the TWI? Those and more questions we want to solve with this project.

• DFG Programme: Research Grants
• International Connection: Japan
• Co-Investigator: Professor Dr. Tilman Birnstiel
• Cooperation Partner: Dr. Takahiro Ueda