Sharp and eccentric rings in debris disks

Structure seen in debris disks - sharp rings, eccentricities, asymmetric ansae - are usually taken as evidence for the gravitational influence of unseen planets, as these disks are mostly gas-free systems of dust and leftover planetesimals. In this simulation we show that if the system has gas, hydrodynamical forces at work suffice to explain the structure seen in debris disks. This gas comes from outgassing of planetesimals and dust grains via sublimation, photodesorption, or collisions, generating a system of dust-to-gas ratio close to unity, where hydrodynamics cannot be ignored. The backreaction of the drag force from the gas onto the dust shepherds rings. The eccentricity can be simply explained by a standing wave propagating along the ring. The planet possibility, though thrilling, is not necessarily required to explain these systems.