GG Tauri's Circumbinary Disk: Models for Near-Infrared Scattered-Light Images and 13CO (J= 1→ 0) Line Profiles

Abstract

We describe models that reproduce the observed near-IR scattered-light images and (CO)-C-13 (J = 1-->0) line profiles from the GG Tau circumbinary disk. The observed extent of the scattered-light images requires a 0.13 M. flared circumbinary disk (as determined from millimeter observations), an inner cleared region of 200 AU, and scale height of 16.6 AU at the disk's inner edge. To reproduce the brightness distribution, we require extinction of the illuminating starlight prior to scattering within the circumbinary disk. This extinction is obtained by including the effects of small circumstellar disks that are coplanar with the circumbinary disk. Further, we find that the effects of geometry and illumination allows the observed scattered-light pattern to be reproduced with a dust grain distribution that fits data from other Taurus-Auriga circumstellar environments. This indicates that unless geometries and illuminations are known, great care must be taken when attempting to determine grain properties from analysis of scattered-light images. The observed (CO)-C-13 line profiles are reproduced using the same geometry adopted for the near-IR modeling. However, we find that the (CO)-C-13 abundance is Power than in the diffuse interstellar medium, in agreement with previous investigations indicating CO depletion in circumstellar environments.