The First Circumstellar Disk Imaged in Silhouette with Adaptive Optics: MagAO Imaging of Orion 218-354

TL;DR

This study presents the first adaptive optics image of a silhouette circumstellar disk in visible light, revealing its structure, optical properties, and grain composition, and models its multiwavelength spectral energy distribution.

Contribution

It provides the first AO image of a silhouette disk in visible light, along with a self-consistent multiwavelength model of the disk's structure and grain properties.

Findings

Disk is likely optically-thin at H-alpha

Only ~10% of disk mass in primitive grains

Inner disk radius is ~15 times larger than sublimation radius

Abstract

We present high resolution adaptive optics (AO) corrected images of the silhouette disk Orion 218-354 taken with Magellan AO (MagAO) and its visible light camera, VisAO, in simultaneous differential imaging (SDI) mode at H-alpha. This is the first image of a circumstellar disk seen in silhouette with adaptive optics and is among the first visible light adaptive optics results in the literature. We derive the disk extent, geometry, intensity and extinction profiles and find, in contrast with previous work, that the disk is likely optically-thin at H-alpha. Our data provide an estimate of the column density in primitive, ISM-like grains as a function of radius in the disk. We estimate that only ~10% of the total sub-mm derived disk mass lies in primitive, unprocessed grains. We use our data, Monte Carlo radiative transfer modeling and previous results from the literature to make the first self-consistent multiwavelength model of Orion 218-354. We find that we are able to reproduce the 1-1000micron SED with a ~2-540AU disk of the size, geometry, small vs. large grain proportion and radial mass profile indicated by our data. This inner radius is a factor of ~15 larger than the sublimation radius of the disk, suggesting that it is likely cleared in the very interior.