Global High-resolution $N$-body Simulation of Planet Formation I. Planetesimal Driven Migration

TL;DR

This study uses high-resolution N-body simulations to examine whether outward planetesimal driven migration occurs when the self-gravity of planetesimals is included, revealing that migration halts due to increased planetesimal velocities.

Contribution

First detailed simulation of planetesimal driven migration including self-gravity, showing migration stops when planetesimal velocities increase, highlighting the role of velocity stirring.

Findings

Runaway growth occurs at disk edges and outside the ice line.

Outward migration of protoplanets is halted by increased planetesimal velocities.

Self-gravity influences the stopping of planetesimal driven migration.

Abstract

We investigated whether outward Planetesimal Driven Migration (PDM) takes place or not in simulations when the self gravity of planetesimals is included. We performed $N$-body simulations of planetesimal disks with large width (0.7 - 4AU) which ranges over the ice line. The simulations consisted of two stages. The first stage simulations were carried out to see the runaway growth phase using the planetesimals of initially the same mass. The runaway growth took place both at the inner edge of the disk and at the region just outside the ice line. This result was utilized for the initial setup of the second stage simulations in which the runaway bodies just outside the ice line were replaced by the protoplanets with about the isolation mass. In the second stage simulations, the outward migration of the protoplanet was followed by the stopping of the migration due to the increase of the random velocity of the planetesimals. Due to this increase of random velocities, one of the PDM criteria derived in Minton and Levison (2014) was broken. In the current simulations, the effect of the gas disk is not considered. It is likely that the gas disk plays an important role in planetesimal driven migration, and we plan to study its effect in future papers.