Discovery of a Disk Gap Candidate at 20 AU in TW Hydrae

TL;DR

This paper reports the detection of a potential disk gap at 20 AU in TW Hydrae using high-contrast polarized light imaging, suggesting possible planet formation or grain growth processes.

Contribution

First high-contrast polarized intensity image revealing a disk depression at 20 AU in TW Hydrae, proposing two scenarios for its origin.

Findings

Detected a polarized intensity depression at ~20 AU

The disk beyond 0.2" is nearly axisymmetric

Proposed two explanations: a gap or grain growth

Abstract

We present a new Subaru/HiCIAO high-contrast H-band polarized intensity (PI) image of a nearby transitional disk associated with TW Hydrae. The scattered light from the disk was detected from 0.2" to 1.5" (11 - 81 AU) and the PI image shows a clear axisymmetric depression in polarized intensity at ~ 0.4" (~ 20 AU) from the central star, similar to the ~ 80 AU gap previously reported from HST images. Azimuthal polarized intensity profile also shows the disk beyond 0.2" is almost axisymmetric. We discuss two possible scenarios explaining the origin of the polarized intensity depression: 1) a gap structure may exist at ~ 20 AU from the central star because of shallow slope seen in the polarized intensity profile, and 2) grain growth may be occurring in the inner region of the disk. Multi-band observations at NIR and millimeter/sub-millimeter wavelengths play a complementary role in investigating dust opacity and may help reveal the origin of the gap more precisely.