Warp and shadows in transitional disks

Ryuta Orihara

Recent high-resolution observations using the Atacama Large Millimeter/sub-millimeter Array (ALMA) have deepened our understanding of protoplanetary disks. Protoplanetary disks are objects composed of dust and gas that rotate around a young star and are thought to be the birthplace of planets. In fact, structures (gap, cavity, spiral, etc.) have been observed in these disks and could have been created by the gravitational interaction between the planet and the disk. Among these, a disk in which a cavity with a radius of several tens of au is observed in the innermost region of the dust disk is called a transitional disk.
Recent high-resolution observations have detected several transitional disks associated with a compact dust disk of radius a few au. Moreover, a centroid velocity map obtained from molecular emission lines shows velocity distortion in the innermost region of the disk. One of the causes is warp. Warp is a structure in which the inclination of the disk changes radially, which is thought to be caused by gravitational interaction between the disk and a planet with an inclined orbit, or by accretion of materials with different angular momentum. If the compact disk is misaligned, this can cast a shadow on the outer disk and create non-axisymmetric temperature.  
We performed radiative transfer calculations using RADMC-3D to investigate shadows made by the warped disk. As the result, the inner disk with the misalignment angle of 10 deg reproduce the shadow pattern of the observed continuum data. Thus, the inner disk may be slightly misaligned with respect to the outer dust ring.