Dust Distribution in Gas Disks. II. Self‐induced Ring Formation through a Clumping Instability

Abstract

Debris rings of dust are found around young luminous stars such asHR 4796A and HD 141569. Some of these entities have sharp edges andgaps, which have been interpreted as evidence for the presence ofshepherding and embedded planets. Here we show that gaps and sharpedges in the debris disks of dust can also be spontaneously self-generatedif they are embedded in optically thin regions of gaseous disks.This clumping instability arises in regions where an enhancementin the dust density leads to local gas temperature and pressure increases.Consequently, the relative motion between the gas and the dust ismodified. The subsequent hydrodynamic drag on the dust particlesleads to further enhancement of their concentration. We show thatthis process is linearly unstable and leads to the formation of ringlikestructures within the estimated lifetime of such young objects. Oncethe gas is removed ( e. g., by photoevaporation), the structuresare "frozen'' and will persist, even when the gas might not be observableanymore.