Early evolution of viscous and self-gravitating circumstellar disks with a dust component
Institute of Fluid Mechanics and Heat Transfer, TU Wien,
2 Research Institute of Physics, Southern Federal University, Stachki Ave. 194, 344090 Rostov-on-Don, Russia
3 Department of Astrophysics, University of Vienna, Vienna 1180, Austria
4 Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya str. 48, 119017 Moscow, Russia
5 Novosibirsk State University, Lavrentieva str. 2, 630090 Novosibirsk, Russia
6 Boreskov Institute of Catalysis, Lavrentieva str. 5, 630090 Novosibirsk, Russia
7 European Southern Observatory (ESO), Karl-Schwarzschild-str. 2, 85748 Garching, Germany
Accepted: 18 January 2018
Context. Aims. The long-term evolution of a circumstellar disk starting from its formation and ending in the T Tauri phase was simulated numerically with the purpose of studying the evolution of dust in the disk with distinct values of the viscous α-parameter and dust fragmentation velocity vfrag.
Methods. We solved numerical hydrodynamics equations in the thin-disk limit, which were modified to include a dust component consisting of two parts: sub-micron-sized dust, and grown dust with a maximum radius ar. The former is strictly coupled to the gas, while the latter interacts with the gas through friction. Dust growth, dust self-gravity, and the conversion of small to grown dust were also considered.
Results. We found that the process of dust growth that is known for the older protoplanetary phase also holds for the embedded phase of the disk evolution. The dust growth efficiency depends on the radial distance from the star – ar is largest in the inner disk and gradually declines with radial distance. In the inner disk, ar is limited by the dust fragmentation barrier. The process of small-to-grown dust conversion is very fast once the disk is formed. The total mass of the grown dust in the disk (beyond 1 AU) reaches tens or even hundreds of Earth masses as soon as in the embedded phase of star formation, and an even greater amount of grown dust drifts in the inner, unresolved 1 AU of the disk. Dust does not usually grow to radii greater than a few cm. A notable exception are models with α ≤ 10−3, in which case a zone with reduced mass transport develops in the inner disk and dust can grow to meter-sized boulders in the inner 10 AU. Grown dust drifts inward and accumulates in the inner disk regions. This effect is most pronounced in the α ≤ 10−3 models, where several hundreds of Earth masses can be accumulated in a narrow region of several AU from the star by the end of embedded phase. The efficiency of grown dust accumulation in spiral arms is stronger near corotation where the azimuthal velocity of dust grains is closest to the local velocity of the spiral pattern. In the framework of the adopted dust growth model, the efficiency of small-to-grown dust conversion was found to increase for lower values of α and vfrag.
Key words: protoplanetary disks / stars: formation / stars: protostars / hydrodynamics
© ESO 2018