Circumstellar Disks of the Most Vigorously Accreting Young Stars

TL;DR

This paper investigates the complex structures of circumstellar disks around young stars experiencing luminous accretion outbursts, revealing gravitational instabilities as a key process in early disk evolution through high-resolution imaging and simulations.

Contribution

It provides high-resolution imaging evidence of arms and arcs in disks during accretion outbursts and links these features to gravitational instabilities via simulations.

Findings

Detected hundreds of AU scale arms and arcs around YSOs

Linked observed structures to gravitational instabilities in disks

Supported models of early disk formation with simulations

Abstract

Young stellar objects (YSOs) may not accumulate their mass steadily, as was previously thought, but in a series of violent events manifesting themselves as sharp stellar brightening. These events can be caused by fragmentation due to gravitational instabilities in massive gaseous disks surrounding young stars, followed by migration of dense gaseous clumps onto the star. We report our high angular resolution, coronagraphic near-infrared polarization imaging observations using the High Contrast Instrument for the Subaru Next Generation Adaptive Optics (HiCIAO) of the Subaru 8.2 m Telescope, towards four YSOs which are undergoing luminous accretion outbursts. The obtained infrared images have verified the presence of several hundred AUs scale arms and arcs surrounding these YSOs. In addition, our hydrodynamics simulations and radiative transfer models further demonstrate that these observed structures can indeed be explained by strong gravitational instabilities occurring at the beginning of the disk formation phase. The effect of those tempestuous episodes of disk evolution on star and planet formation remains to be understood.