Direct Imaging of Fine Structures in Giant Planet Forming Regions of the Protoplanetary Disk around AB Aurigae

Abstract

We report high-resolution 1.6 \micron polarized intensity ($PI$) images of the circumstellar disk around the Herbig Ae star AB Aur at a radial distance of 22 AU ($0."15$) up to 554 AU (3.$"$85), which have been obtained by the high-contrast instrument HiCIAO with the dual-beam polarimetry. We revealed complicated and asymmetrical structures in the inner part ($\lesssim$140 AU) of the disk, while confirming the previously reported outer ($r$ $\gtrsim$200 AU) spiral structure. We have imaged a double ring structure at $\sim$40 and $\sim$100 AU and a ring-like gap between the two. We found a significant discrepancy of inclination angles between two rings, which may indicate that the disk of AB Aur is warped. Furthermore, we found seven dips (the typical size is $\sim$45 AU or less) within two rings as well as three prominent $PI$ peaks at $\sim$40 AU. The observed structures, including a bumpy double ring, a ring-like gap, and a warped disk in the innermost regions, provide essential information for understanding the formation mechanism of recently detected wide-orbit ($r$ $>$20 AU) planets.