Formation of multiple dust rings and gaps in protoplanetary discs by a single migrating planet. A parameter study in locally isothermal discs

Formation of multiple dust rings and gaps in protoplanetary discs by a single migrating planet. A parameter study in locally isothermal discs
S"oren C. Meiners, Kim M. Weiskopf, Thomas Rometsch, Cornelis P. Dullemond
arXiv:2608.11312v1 Announce Type: new
Abstract: ALMA observations show that large protoplanetary discs usually contain multiple concentric dust rings separated by dark gaps. A natural explanation is dust-trapping at the edges of gaps opened by newly formed planets. However, planets typically migrate inward on timescales shorter than disc lifetimes, seemingly at odds with rings at large radii. We aim to investigate the conditions under which migrating planets can form long-lived, multi-ringed structures out to $rsim 150$ au to constrain the parameter space for the planetary origin hypothesis of rings. Using the FargoCPT hydrodynamics code, we ran two-dimensional, locally isothermal disc models with a single migrating planet, varying disc aspect ratio, viscosity ($alpha$), and planetary mass. In all models, the planet eventually stalls in a deep gap. At $alphaleq 10^{-4}$, secondary spirals launched by the planet can open additional gaps at smaller radii. When planets exceed twice the local thermal mass before stalling, they enter a regime of alternating slow and type-III rapid migration, leaving partial gaps outside their orbit. The gap edges consistently feature pressure maxima that trap dust. These begin as large vortices at $alphaleq 10^{-4}$, but gradually smear out into rings before dissipating. The type-III remnant rings dissipate quickly at $alpha=10^{-3}$, but persist for at least 300-500 kyr at $alphaleq 10^{-4}$. Both smear-out and dissipation timescales increase with lower $alpha$. Our results show that migrating planets can reproduce observed multi-ringed structures in discs with $alphalesssim 10^{-4}$ through their stall ($rlesssim 50$ au), secondary gap-opening ($rlesssim 20$ au), and type-III migration remnants (extending to $rsim 150$ au for Jupiter-mass planets in sufficiently massive discs). Longer simulations will be required to compare the statistics of ring-to-vortex occurrence to observations.arXiv:2608.11312v1 Announce Type: new
Abstract: ALMA observations show that large protoplanetary discs usually contain multiple concentric dust rings separated by dark gaps. A natural explanation is dust-trapping at the edges of gaps opened by newly formed planets. However, planets typically migrate inward on timescales shorter than disc lifetimes, seemingly at odds with rings at large radii. We aim to investigate the conditions under which migrating planets can form long-lived, multi-ringed structures out to $rsim 150$ au to constrain the parameter space for the planetary origin hypothesis of rings. Using the FargoCPT hydrodynamics code, we ran two-dimensional, locally isothermal disc models with a single migrating planet, varying disc aspect ratio, viscosity ($alpha$), and planetary mass. In all models, the planet eventually stalls in a deep gap. At $alphaleq 10^{-4}$, secondary spirals launched by the planet can open additional gaps at smaller radii. When planets exceed twice the local thermal mass before stalling, they enter a regime of alternating slow and type-III rapid migration, leaving partial gaps outside their orbit. The gap edges consistently feature pressure maxima that trap dust. These begin as large vortices at $alphaleq 10^{-4}$, but gradually smear out into rings before dissipating. The type-III remnant rings dissipate quickly at $alpha=10^{-3}$, but persist for at least 300-500 kyr at $alphaleq 10^{-4}$. Both smear-out and dissipation timescales increase with lower $alpha$. Our results show that migrating planets can reproduce observed multi-ringed structures in discs with $alphalesssim 10^{-4}$ through their stall ($rlesssim 50$ au), secondary gap-opening ($rlesssim 20$ au), and type-III migration remnants (extending to $rsim 150$ au for Jupiter-mass planets in sufficiently massive discs). Longer simulations will be required to compare the statistics of ring-to-vortex occurrence to observations.