Molecules with ALMA at Planet-forming Scales (MAPS) XIV: Revealing disk substructures in multi-wavelength continuum emission

TL;DR

This study uses high-resolution ALMA observations to analyze dust properties and substructures in planet-forming disks, revealing variations in grain size, dust trapping, and gravitational stability across multiple disks.

Contribution

It provides new constraints on dust distribution and grain sizes in disks, including effects of dust scattering, and assesses gravitational stability in the context of observed substructures.

Findings

Dust surface density peaks at bright rings, consistent with dust trapping models.

Maximum grain sizes decrease from ~1 cm to 1 mm from inner to outer disk regions.

Only IM Lup shows gravitational instability based on Toomre parameter analysis.

Abstract

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 few hundred micrometer sizes. 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.