Protoplanetary disk dynamics in high dust-to-gas ratio environments

Gárate Silva, Matías (2020): Protoplanetary disk dynamics in high dust-to-gas ratio environments. Dissertation, LMU München: Fakultät für Physik

Abstract

Protoplanetary disks are the birthplace of planets. Gas and dust orbit around the central star subject to the forces of gravity, pressure, turbulence, and mutual drag. With the advent of the new telescopes, we need more than ever accurate models to interpret the observations of disks, which display a wide variety of substructures. In this work we study the effect of the mutual drag force between gas and dust on protoplanetary disk dynamics and evolution, particularly in the cases where the dust-to-gas ratio is high enough for the solids to become dynamically important. We derive the collective gas and dust dynamics from the momentum conservation equations, by including the back-reaction from the dust to the gas drag force, and considering the contribution of multiple dust species. The resulting velocities are implemented into the protoplanetary disk evolution codes Dustpy and Twopoppy, that solve the advection of the gas and dust components of the protoplanetary disk, along with the growth of solids through coagulation and fragmentation. Finally, we combine our equations for the fluid dynamics with different disk scenarios, including: the re-activation of a dead zone, the evaporation and condensation of water at the snowline, and the evolution of a photo-evaporative disk. We characterize the effect of dust back-reaction on the gas and dust dynamics in the different scenarios. We find that in the event of a dead zone re-activation the high dust content accumulated in the inner regions damps the collective disk motion, since more material is carried away by the same viscous force. At the snowline the dust back-reaction can stop the gas flow, disconnect the inner and outer disk in terms of gas accretion, and enhance both the radial extend and the level concentration of dust accumulations. Also, dust rings formed at the edge of a photo-evaporative gap are spread over a wider area, since the dust back-reaction smooths the gas pressure profile by pushing the material away from the pressure maximum. Lastly, we find that the back-reaction only affects the disk motion in environments with high dust-to-gas ratios, low turbulent viscosity, and large particle sizes. Our work shows the effects of the the dust back-reaction on the global disk dynamics, and can be used to better characterize observational signatures, by providing a more accurate model for the dust distribution, as well as a guideline to assess whether the dust back-reaction should be considered, given the disk conditions.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 530 Physik
• Fakultäten: Fakultät für Physik
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 24. September 2020
• 1. Bericht­erstatter:in: Birnstiel, Til