Formation of pebbles in (gravito-)viscous protoplanetary disks with various turbulent strengths

TL;DR

This study investigates how different levels of turbulent viscosity influence dust growth and pebble formation in self-gravitating protoplanetary disks through hydrodynamics simulations, revealing that turbulence strength significantly affects pebble distribution.

Contribution

It provides new insights into the combined effects of turbulence and gravitational instability on dust and pebble formation in protoplanetary disks, using detailed hydrodynamics simulations.

Findings

High turbulence suppresses pebble formation and leads to a more uniform dust distribution.

Lower turbulence allows gravitational instability to dominate, causing ring-like dust accumulation.

The spatial variation of effective viscosity influences the disk's dust and gas dynamics.

Abstract

Aims. Dust plays a crucial role in the evolution of protoplanetary disks. We study the dynamics and growth of initially sub-$\mu m$ dust particles in self-gravitating young protoplanetary disks with various strengths of turbulent viscosity. We aim to understand the physical conditions that determine the formation and spatial distribution of pebbles when both disk self-gravity and turbulent viscosity can be concurrently at work. Methods. We perform the thin-disk hydrodynamics simulations of self-gravitating protoplanetary disks over an initial time period of 0.5 Myr using the FEOSAD code. Turbulent viscosity is parameterized in terms of the spatially and temporally constant $\alpha$-parameter, while the effects of gravitational instability on dust growth is accounted for by calculating the effective parameter $\alpha_{\rm GI}$. We consider the evolution of dust component including momentum exchange with gas, dust self-gravity, and also a simplified model of dust growth. Results. We find that the level of turbulent viscosity strongly affects the spatial distribution and total mass of pebbles in the disk. The $\alpha=10^{-2}$ model is viscosity-dominated, pebbles are completely absent, and dust-to-gas mass ratio deviates from the reference 1:100 value no more than by 30\% throughout the disk extent. On the contrary, the $\alpha=10^{-3}$ model and, especially, the $\alpha=10^{-4}$ model are dominated by gravitational instability. The effective parameter $\alpha+\alpha_{\rm GI}$ is now a strongly varying function of radial distance. As a consequence, a bottle neck effect develops in the innermost disk regions, which makes gas and dust accumulate in a ring-like structure. Abridged.