Three radial gaps in the disk of TW Hydrae imaged with SPHERE

TL;DR

This study uses high-resolution imaging and radiative transfer modeling to identify and analyze three radial gaps in the TW Hydrae disk, suggesting potential low-mass planet formation and providing insights into disk structure.

Contribution

The paper presents the first high-resolution polarized light images of TW Hydrae revealing three radial gaps and introduces a radiative transfer model including dust settling to constrain gas distribution.

Findings

Three radial gaps at 6, 21, and 85 au identified in the disk.

Gas surface density in gaps reduced by 50-80%.

Low-mass planets (a few 10 Earth masses) could explain the gaps.

Abstract

We present scattered light images of the TW Hya disk performed with SPHERE in PDI mode at 0.63, 0.79, 1.24 and 1.62 micron. We also present H2/H3-band ADI observations. Three distinct radial depressions in the polarized intensity distribution are seen, around 85, 21, and 6~au. The overall intensity distribution has a high degree of azimuthal symmetry; the disk is somewhat brighter than average towards the South and darker towards the North-West. The ADI observations yielded no signifiant detection of point sources in the disk. Our observations have a linear spatial resolution of 1 to 2au, similar to that of recent ALMA dust continuum observations. The sub-micron sized dust grains that dominate the light scattering in the disk surface are strongly coupled to the gas. We created a radiative transfer disk model with self-consistent temperature and vertical structure iteration and including grain size-dependent dust settling. This method may provide independent constraints on the gas distribution at higher spatial resolution than is feasible with ALMA gas line observations. We find that the gas surface density in the "gaps" is reduced by 50% to 80% relative to an unperturbed model. Should embedded planets be responsible for carving the gaps then their masses are at most a few 10 Mearth. The observed gaps are wider, with shallower flanks, than expected for planet-disk interaction with such low-mass planets. If forming planetary bodies have undergone collapse and are in the "detachted phase" then they may be directly observable with future facilities such as METIS at the E-ELT.