The Structure of the Evolved Circumbinary Disk around V4046 Sgr

TL;DR

This study reveals a large inner hole and a narrow dust ring in the V4046 Sgr protoplanetary disk, indicating dust accumulation possibly due to a low-mass companion or photoevaporation, with implications for planet formation.

Contribution

First high-resolution imaging and modeling of the V4046 Sgr disk revealing detailed dust and gas structure, including a large inner hole and a narrow dust ring.

Findings

Large inner hole of 29 AU in the disk.

Dust concentrated in a narrow ring at 37 AU.

Significant variation in dust-to-gas ratio across the disk.

Abstract

We present sensitive, sub-arcsecond resolution Submillimeter Array observations of the protoplanetary disk around the nearby, pre-main sequence spectroscopic binary V4046 Sgr. We report for the first time a large inner hole (r=29 AU) spatially resolved in the 1.3 mm continuum emission and study the structure of this disk using radiative transfer calculations to model the spectral energy distribution (SED), continuum visibilities, and spectral line emission of CO and its main isotopologues. Our modeling scheme demonstrates that the majority of the dust mass is distributed in a narrow ring (centered at 37 AU with a FWHM of 16 AU) that is ~5 times more compact than the gas disk. This structure implies that the dust-to-gas mass ratio has a strong spatial variation, ranging from a value much larger than typical of the interstellar medium (ISM) at the ring to much smaller than that of the ISM at larger disk radii. We suggest that these basic structural features are potentially observational signatures of the accumulation of solids at a local gas pressure maximum. These models also require a substantial population of ~micron-sized grains inside the central disk cavity. We suggest that this structure is likely the result of dynamical interactions with a low-mass companion, although photoevaporation may also play a secondary role.