A Resolved Near-Infrared Image of The Inner Cavity in The GM Aur Transitional Disk

TL;DR

This study provides high-resolution near-infrared polarized images of the GM Aur transitional disk, revealing a smaller inner cavity than submillimeter observations, suggesting complex cavity formation processes involving potential planetary influence and grain growth.

Contribution

First direct high-contrast near-infrared imaging of GM Aur's inner cavity, revealing discrepancies with submillimeter data and implications for cavity formation mechanisms.

Findings

Inner cavity radius measured at 18±2 au in near-infrared

Discrepancy between near-infrared and submillimeter cavity sizes

Evidence suggesting additional processes beyond dust filtration

Abstract

We present high-contrast H-band polarized intensity (PI) images of the transitional disk around the young solar-like star GM Aur. The near-infrared direct imaging of the disk was derived by polarimetric differential imaging using the Subaru 8.2-m Telescope and HiCIAO. An angular resolution and an inner working angle of 0."07 and r~0."05, respectively, were obtained. We clearly resolved a large inner cavity, with a measured radius of 18+/-2 au, which is smaller than that of a submillimeter interferometric image (28 au). This discrepancy in the cavity radii at near-infrared and submillimeter wavelengths may be caused by a 3-4M_Jup planet about 20 au away from the star, near the edge of the cavity. The presence of a near-infrared inner is a strong constraint on hypotheses for inner cavity formation in a transitional disk. A dust filtration mechanism has been proposed to explain the large cavity in the submillimeter image, but our results suggest that this mechanism must be combined with an additional process. We found that the PI slope of the outer disk is significantly different from the intensity slope obtained from HST/NICMOS, and this difference may indicate the grain growth process in the disk.