N-Body Simulation of Planetesimal Formation through Gravitational Instability of a Dust Layer in Laminar Gas Disk

Abstract

We investigate the formation process of planetesimals from the dust layer by the gravitational instability in the gas disk using local $N$-body simulations. The gas is modeled as a background laminar flow. We study the formation process of planetesimals and its dependence on the strength of the gas drag. Our simulation results show that the formation process is divided into three stages qualitatively: the formation of wake-like density structures, the creation of planetesimal seeds, and their collisional growth. The linear analysis of the dissipative gravitational instability shows that the dust layer is secularly unstable although Toomre's $Q$ value is larger than unity. However, in the initial stage, the growth time of the gravitational instability is longer than that of the dust sedimentation and the decrease in the velocity dispersion. Thus, the velocity dispersion decreases and the disk shrinks vertically. As the velocity dispersion becomes sufficiently small, the gravitational instability finally becomes dominant. Then wake-like density structures are formed by the gravitational instability. These structures fragment into planetesimal seeds. The seeds grow rapidly owing to mutual collisions.

32 pages, 11 figures, accepted for publication in ApJ

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Cited by in corpus (12)

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• An Origin of Multiple Ring Structure and Hidden Planets in HL Tau: A Unified Picture by Secular Gravitational Instability
• On the accumulation of planetesimals near disc gaps created by protoplanets
• The formation of planets in circumbinary disks
• Making Planet Nine: Pebble Accretion at 250--750 AU in a Gravitationally Unstable Ring
• Secular Gravitational Instability of a Dust Layer in Shear Turbulence
• Dust Concentration at the Boundary Between Steady Super/Sub-Keplerian Flow Created by Inhomogeneous Growth of MRI
• Global drag-induced instabilities in protoplanetary disks
• Planetesimal Formation by Gravitational Instability of a Porous-Dust Disk
• Dynamics of Porous Dust Aggregates and Gravitational Instability of Their Disk