A ring-like concentration of mm-sized particles in Sz 91

TL;DR

This paper presents high-resolution ALMA observations of Sz 91, revealing a narrow ring of large dust grains at 110 au and a more extended gas disc, supporting models of planet-disc interactions.

Contribution

First detailed ALMA imaging of Sz 91 showing a distinct ring of large dust grains, confirming theoretical predictions of planet-disc interaction effects.

Findings

Large dust grains are concentrated in a narrow ring at 110 au.

Gas emission extends much further than the dust ring.

Observations agree with hydrodynamical models of planet-disc interactions.

Abstract

Models of planet formation and disc evolution predict a variety of observables in the dust structure of protoplanetary discs. Here we present Atacama Large Millimeter/submillimeter Array (ALMA) Band-6 and Band-7 observations of the transition disc Sz\,91 showing that the continuum emission at 870$\mu$m, which is dominated by emission from large dust grains, is localized in an optically thin narrow ring. We find that most of the emission ($\sim95\%$) is concentrated in a ring located at 110 au from the central star that is only about 44 au wide. In contrast, the $^{12}\mathrm{CO}$ (2-1) emission peaks closer to the star and is detected up to $\sim488$ au from the star. The concentration of large grains in a ring-like structure while the gas disc extends much further in and further out is in qualitative agreement with predictions of hydrodynamical models of planet-disc interactions including radial drift and gas drag.