Polarimetric Imaging of Large Cavity Structures in the Pre-transitional Protoplanetary Disk around PDS 70: Observations of the disk

TL;DR

This study provides high-resolution polarimetric imaging of the PDS 70 protoplanetary disk, revealing a large inner gap, disk geometry shifts, and constraining potential unseen companions, advancing understanding of disk structure and planet formation.

Contribution

First high-resolution polarimetric imaging of PDS 70's disk revealing a giant inner gap and disk geometry shifts, with modeling constraining potential unseen companions.

Findings

Resolved a ~70 AU inner gap in the disk.

Confirmed the brown dwarf candidate as a background star.

Placed upper mass limits of 30-50 MJ for potential companions within the gap.

Abstract

We present high resolution H-band polarized intensity (PI; FWHM = 0."1: 14 AU) and L'-band imaging data (FWHM = 0."11: 15 AU) of the circumstellar disk around the weak-lined T Tauri star PDS 70 in Centaurus at a radial distance of 28 AU (0."2) up to 210 AU (1."5). In both images, a giant inner gap is clearly resolved for the first time, and the radius of the gap is ~70 AU. Our data show that the geometric center of the disk shifts by ~6 AU toward the minor axis. We confirm that the brown dwarf companion candidate to the north of PDS 70 is a background star based on its proper motion. As a result of SED fitting by Monte Carlo radiative transfer modeling, we infer the existence of an optically thick inner disk at a few AU. Combining our observations and modeling, we classify the disk of PDS 70 as a pre-transitional disk. Furthermore, based on the analysis of L'-band imaging data, we put an upper limit mass of companions at ~30 to ~50MJ within the gap. Taking account of the presence of the large and sharp gap, we suggest that the gap could be formed by dynamical interactions of sub-stellar companions or multiple unseen giant planets in the gap.