Molecules with ALMA at Planet-forming Scales (MAPS). XIV. Revealing Disk Substructures in Multiwavelength Continuum Emission

Constraining dust properties of planet-forming disks via high-angular-resolution observations is fundamental to understanding how solids are trapped in substructures and how dust growth may be favored or accelerated therein. We use ALMA dust continuum observations of the Molecules with ALMA at Planet-forming Scales (MAPS) disks and explore a large parameter space to constrain the radial distribution of solid mass and maximum grain size in each disk, including or excluding dust scattering. In the nonscattering model, the dust surface density and maximum grain size profiles decrease from the inner disks to the outer disks, with local maxima at the bright ring locations, as expected from dust trapping models. The inferred maximum grain sizes from the inner to outer disks decrease from 1 cm to 1 mm. For IM Lup, HD 163296, and MWC 480 in the scattering model, two solutions are compatible with their observed inner disk emission: one solution corresponding to a maximum grain size of a few millimeters (similar to the nonscattering model), and the other corresponding to a size of a few hundred micrometers. Based on the estimated Toomre parameter, only IM Lup-which shows a prominent spiral morphology in millimeter dust-is found to be gravitationally unstable. The estimated maximum Stokes number in all the disks lies between 0.01 and 0.3, and the estimated turbulence parameters in the rings of AS 209 and HD 163296 are close to the threshold where dust growth is limited by turbulent fragmentation. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Automated summary

Constraining dust properties of planet-forming disks through high-angular-resolution observations reveals that the dust mass and maximum grain size decrease from the inner to outer disks, with local maxima at bright ring locations, in line with dust trapping models. The disk of IM Lup exhibits gravitational instability, while the estimated maximum Stokes numbers and turbulence parameters in AS 209 and HD 163296 are close to the threshold where dust growth is limited by turbulent fragmentation.