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

Debris rings of dust are found around young luminous stars such as HR4796Aand HD141569. Some of these entities have sharp edges and gaps which have beeninterpreted as evidence for the presence of shepherding and embedded planets.Here we show that gaps and sharp edges in the debris disks of dust can also bespontaneously self generated if they are embedded in optically thin regions ofgaseous 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 is modified. Thesubsequent hydrodynamic drag on the dust particles leads to further enhancementof their concentration. We show that this process is linearly unstable andleads to the formation of ring-like structures within the estimated life timeof such young objects. Once the gas is removed (e.g. by photo evaporation) thestructures are ``frozen'' and will persist, even when the gas might not beobservable anymore.Comment: 24 pages, 6 figures, ApJ in pres