# The Disk Substructures at High Angular Resolution Project (DSHARP) VI: Dust trapping in thin-ringed protoplanetary disks

## TL;DR

This study uses high-resolution ALMA observations and analytical modeling to confirm that narrow, circular dust rings in protoplanetary disks are caused by dust trapping in pressure bumps, providing insights into disk physics and planet formation.

## Contribution

It demonstrates that all observed rings are consistent with dust trapping, constrains the physical conditions of the rings, and rules out certain turbulence and grain size models.

## Key findings

- All rings are consistent with dust trapping.
- Several rings are narrower than the pressure scale height.
- Dust masses in rings are tens of Earth masses.

## Abstract

A large fraction of the protoplanetary disks observed with ALMA display multiple well-defined and nearly perfectly circular rings in the continuum, in many cases with substantial peak-to-valley contrast. The DSHARP campaign shows that several of these rings are very narrow in radial extent. In this paper we test the hypothesis that these dust rings are caused by dust trapping in radial pressure bumps, and if confirmed, put constraints on the physics of the dust trapping mechanism. We model this process analytically in 1D, assuming axisymmetry. By comparing this model to the data, we find that all rings are consistent with dust trapping. Based on a plausible model of the dust temperature we find that several rings are narrower than the pressure scale height, providing strong evidence for dust trapping. The rings have peak absorption optical depth in the range between 0.2 and 0.5. The dust masses stored in each of these rings is of the order of tens of Earth masses, though much ambiguity remains due to the uncertainty of the dust opacities. The dust rings are dense enough to potentially trigger the streaming instability, but our analysis cannot give proof of this mechanism actually operating. Our results show, however, that the combination of very low alpha_turb << 5e-4 and very large grains a_grain >> 0.1 cm can be excluded by the data for all the rings studied in this paper.