Shadow-based Framework for Estimating Transition Disk Geometries

Abstract Some transition disks host misaligned inner disks with radii of several astronomical units. Understanding the geometric and physical properties of these misaligned disks is essential for advancing terrestrial planet formation models. This study introduces a novel method to infer the three-dimensional structures of both inner and outer disks by analyzing nonaxisymmetric shadows and the horizon in optical and infrared scattered light images of the outer disk. This method was applied to the HD 100453 system, in which infrared scattered light images from the Very Large Telescope revealed disk shadows. These results indicate that the inner disk is misaligned by ∼70° relative to the outer disk, which is consistent with the results of previous studies. The aspect ratio of the inner disk surface was estimated to be 0.17, which may reflect the surface height of the optically thick dusty component due to vertical lofting by MHD winds or turbulence. In addition, the surface height distribution of the outer disk was characterized, providing novel insights into its vertical structure.