Extracting Non-Axisymmetric Structures from the Interferometric Observations of Protoplanetary Disks

Takayuki Muto

ALMA has found that protoplanetary disks have rich structures such as gaps, rings and vortices. Non-axisymmetric structures are considered to be the signature of dynamical processes occurring in protoplanetary disks and closely related to ongoing planet formation. The directly observed quantity by an interferomer such as ALMA is visibility, which is an incomplete set of the spatial Fourier Transform of the brightness distribution on sky. Images reconstructed from the visibilities sometimes have artificial signals due to the incompleteness of the observable visibilities. In this poster, we present a formulation and method to extract large scale non-axisymmetric signature in the disk. The analyses are formulated fully in the visibility domain so the method is free of uncertainty arising from the image reconstruction processes (e.g., CLEAN). With the application to the real data obtained by ALMA, we show that it is possible to extract the asymmetric signatures with the spatial scale smaller than typical CLEAN beam size. The method will be useful to detect the asymmetry in the inner region with several to ten au from the central star, which corresponds to the region where planets are located in the case of Solar System.