SCATTERED LIGHT FROM DUST IN THE CAVITY OF THE V4046 Sgr TRANSITION DISK

ABSTRACT We report the presence of scattered light from dust grains located in the giant planet formation region of the circumbinary disk orbiting the ∼20 Myr old close (∼0.045 AU separation) binary system V4046 Sgr AB based on observations with the new Gemini Planet Imager (GPI) instrument. These GPI images probe to within ∼7 AU of the central binary with a linear spatial resolution of ∼3 AU, and are therefore capable of revealing the dust disk structure within a region corresponding to the giant planets in our solar system. GPI imaging reveals a relatively narrow (FWHM ∼ 10 AU) ring of polarized near-infrared flux whose brightness peaks at ∼14 AU. This ∼14 AU radius ring is surrounded by a fainter outer halo of scattered light extending to ∼45 AU, which coincides with previously detected millimeter-wave thermal dust emission. The presence of small grains that efficiently scatter starlight well inside the millimeter-wavelength disk cavity supports current models of planet formation which suggest that planet-disk interactions can generate pressure traps that impose strong radial variations in the particle size distribution throughout the disk.