Ring formation by coagulation of dust aggregates in early phase of disk evolution around a protostar

TL;DR

This study models how dust coagulation in early protostellar disks can produce observable ring structures, aligning with observations of young stellar objects and shedding light on early disk evolution.

Contribution

It introduces a dust coagulation model that explains ring formation as a growth front in early-stage disks, supported by radiative transfer calculations.

Findings

Growth front corresponds to observable ring structures.

Observed ring positions match model predictions for young stellar objects.

Dust surface density sharply changes at the growth front.

Abstract

Ring structures are observed by (sub-)millimeter dust continuum emission in various circumstellar disks from early stages of Class 0 and I to late stage of Class II young stellar objects (YSOs). In this paper, we study one of the possible scenarios of such ring formation in early stage, which is coagulation of dust aggregates. The dust grains grow in an inside-out manner because the growth timescale is roughly proportional to the orbital period. The boundary of the dust evolution can be regarded as the growth front, where the growth time is comparable to the disk age. With radiative transfer calculations based on the dust coagulation model, we find that the growth front can be observed as a ring structure because dust surface density is sharply changed at this position. Furthermore, we confirm that the observed ring positions in the YSOs with an age of $\lesssim1$ Myr are consistent with the growth front. The growth front could be important to create the ring structure in particular for early stage of the disk evolution such as Class 0 and I sources.