Dust distribution in circumstellar disks harboring multi-planet systems

I. Sub-thermal mass planets

¹ Dipartimento di Fisica e Astronomia “G. Galilei”, Università degli Studi di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
² Universitäts-Sternwarte, Ludwig-Maximilians-Universität München, Scheinerstr. 1, München, 81679, Bayern, Germany
³ Dipartimento di Fisica e Astronomia “G. Galilei”, Università degli Studi di Padova, Via Marzolo 8, 35121 Padova, Italy

^★ Corresponding authors: vincenzo.roatti@phd.unipd.it; picogna@usm.lmu.de; francesco.marzari@pd.infn.it

Received: 17 July 2025
Accepted: 22 October 2025

Abstract

Aims. We investigate the formation of dust gaps in circumstellar disks driven by the presence of multiple low-mass planets, focusing on the distinct physical mechanisms that operate across different gas-dust coupling regimes.

Methods. We performed 2D hydrodynamical simulations of multiple planets embedded in a circumstellar disk using the PLUTO code, with the addition of dust treated as Lagrangian particles with a multi-size distribution. We carried out a large parameter space analysis to check the influence of disk and planetary properties on the dust component.

Results. Planets with m ≳ 1 M_⊕ can open dust gaps for small grains in dense and warm disks (strong coupling) and for large grains in thin and cold disks (weak coupling), without significantly perturbing the gas. In the strong coupling regime, rapid Type I migration can shift the gap location inward or outward with respect to the planetary orbit, depending on the direction of migration. We also find dust gaps that overlap with Lindblad resonances. In the weak coupling regime, planets can create an inner dust cavity, multiple dust rings, or hide inside a common gap.

Conclusions. Our results show how low-mass multi-planet systems perturb the dust distribution, which cannot be explained by considering each planet in isolation and has a crucial dependence on local disk conditions and dust grain sizes.