Ring-Gap Structures in the Class I Circumstellar Disk of CrA IRS 2 Associated with Magnetic Flux-Driven Bubble

TL;DR

This study uses advanced imaging techniques on ALMA data to reveal early-stage disk structures around a young protostar, suggesting planet formation may occur earlier than previously thought due to magnetic flux effects.

Contribution

First high-resolution imaging of a Class I disk showing inner hole and outer ring-gap structures, indicating early planet formation influenced by magnetic flux dissipation.

Findings

Detected inner hole and outer ring-gap structures in the disk.

Estimated potential planet mass of 0.1-1.8 Jupiter masses.

Proposed magnetic flux dissipation facilitates early planet formation.

Abstract

Recent ALMA observations with 0''.1 resolution reveal characteristic substructures in circumstellar disks around young Class I sources, providing clues to the early stages of morphological disk evolution. In this paper, we applied PRIISM imaging to ALMA archival Band 6 continuum data of the circumstellar disk around the Class I protostar CrA IRS 2, located in the Corona Australis molecular cloud, which is associated with an extended gas ring attributed to magnetic flux advection driven by interchange instability. The dust continuum image with 1.5 times higher spatial resolution than conventional imaging revealed, for the first time, the early-phase circumstellar disk with both inner central hole and outer ring-gap structures, making CrA IRS 2 the youngest system exhibiting such features based on the bolometric temperature of $T_{\rm bol}$=235 K. To examine planet-disk interaction as one possible origin of the outer ring-gap structure, we found the measured depth and width to be consistent with planet-disk interaction models, suggesting the existence of a giant planet with a mass of 0.1-1.8 $M_{\rm Jup}$. The additional mechanism required for rapid planet formation could be the magnetic flux dissipation driven by the interchange instability, which suppresses MRI-driven turbulence and extends the dead zone, allowing efficient dust growth and the early formation of planets. This system thus provides new insight into how substructures and planet formation can emerge during the early, accreting phase of disk evolution.