Dust ring and gap formation by gas flow induced by low-mass planets embedded in protoplanetary disks

I. Steady-state model

¹ Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8551, Japan
e-mail: kuwahara.a.aa@m.titech.ac.jp
² Earth-Life Science Institute, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550, Japan
³ National Institute of Technology, Ichinoseki College, Takanashi, Hagisho, Ichinoseki-shi, Iwate 021-8511, Japan

Received: 22 April 2022
Accepted: 27 June 2022

Abstract

Context. Recent high-spatial-resolution observations have revealed dust substructures in protoplanetary disks such as rings and gaps, which do not always correlate with gas. Because radial gas flow induced by low-mass, non-gas-gap-opening planets could affect the radial drift of dust, it potentially forms these dust substructures in disks.

Aims. We investigate the potential of gas flow induced by low-mass planets to sculpt the rings and gaps in the dust profiles.

Methods. We first perform three-dimensional hydrodynamical simulations, which resolve the local gas flow past a planet. We then calculate the trajectories of dust influenced by the planet-induced gas flow. Finally, we compute the steady-state dust surface density by incorporating the influences of the planet-induced gas flow into a one-dimensional dust advection-diffusion model.

Results. The outflow of the gas toward the outside of the planetary orbit inhibits the radial drift of dust, leading to dust accumulation (the dust ring). The outflow toward the inside of the planetary orbit enhances the inward drift of dust, causing dust depletion around the planetary orbit (the dust gap). Under weak turbulence (α_diff ≲ 10⁻⁴, where α_diff is the turbulence strength parameter), the gas flow induced by the planet with ≳1M_⊕ (Earth mass) generates the dust ring and gap in the distribution of small dust grains (≲1 cm) with a radial extent of ~1–10 times the gas scale height around the planetary orbit without creating a gas gap and pressure bump.

Conclusions. The gas flow induced by low-mass, non-gas-gap-opening planets can be considered a possible origin of the observed dust substructures in disks. Our results may be helpful in explaining the disks whose dust substructures were found not to correlate with those of the gas.