A New Algorithm for Self-Consistent 3-D Modeling of Collisions in Dusty Debris Disks

TL;DR

This paper introduces a new algorithm for 3D modeling of debris disks that accounts for collisions, revealing how collisions influence disk morphology and dust distribution, with implications for interpreting observations of systems like Fomalhaut.

Contribution

The paper presents a novel 'collisional grooming' algorithm that efficiently models collisional effects in debris disks, including particle fragmentation and size sorting, in three dimensions.

Findings

Collision rates are higher in resonant ring structures.

Collisions can smooth out sharp features in disk morphology.

Size sorting by collisions affects disk appearance at different wavelengths.

Abstract

We present a new "collisional grooming" algorithm that enables us to model images of debris disks where the collision time is less than the Poynting Robertson time for the dominant grain size. Our algorithm uses the output of a collisionless disk simulation to iteratively solve the mass flux equation for the density distribution of a collisional disk containing planets in 3 dimensions. The algorithm can be run on a single processor in ~1 hour. Our preliminary models of disks with resonant ring structures caused by terrestrial mass planets show that the collision rate for background particles in a ring structure is enhanced by a factor of a few compared to the rest of the disk, and that dust grains in or near resonance have even higher collision rates. We show how collisions can alter the morphology of a resonant ring structure by reducing the sharpness of a resonant ring's inner edge and by smearing out azimuthal structure. We implement a simple prescription for particle fragmentation and show how Poynting-Robertson drag and fragmentation sort particles by size, producing smaller dust grains at smaller circumstellar distances. This mechanism could cause a disk to look different at different wavelengths, and may explain the warm component of dust interior to Fomalhaut's outer dust ring seen in the resolved 24 micron Spitzer image of this system.