Oral Presentation

Survival of ALMA Rings in the absence of Pressure Maximum

Author(s): Haochang Jiang (Tsinghua University), Chris W. Ormel (Tsinghua University)

Presenter: Haochang Jiang (Tsinghua University)

Recent ALMA observations have revealed that a large fraction of protoplanetary discs contain bright rings at (sub)millimeter wavelengths. Dust trapping induced by pressure maxima in the gas disc is a popular explanation for these rings. However, it is unclear whether such pressure bumps can survive for evolutionary timescales of the disc. In this work, we investigate an alternative scenario, which involves only dust-gas interactions in a smooth gas disc. We postulate that ALMA rings are a manifestation of a dense, clumpy midplane that is actively forming planetesimals. The clumpy medium itself hardly experiences radial drift, but clumps lose mass by disintegration and vertical transport and planetesimal formation. Starting from a seed ring, we numerically solve the transport equations to investigate the ring’s survival. In general, rings move outward, due to diffusion of the clump component. Without pressure support, rings leak material at rates ∼40