Modeling the arc and ring structures in the HD 143006 disk

Rings and asymmetries in protoplanetary disks are considered as signposts of ongoing planet formation.In this work,we con-duct three-dimensional radiative transfer simulations to model the intriguing disk around HD143006 that has three dust rings and a bright arc.A complex geometric configuration,with a misaligned inner disk,is assumed to account for the asymmetric structures.The two-dimensional surface density is constructed by iteratively fitting the ALMA data.We find that the dust tem-perature displays a notable discontinuity at the boundary of the misalignment.The ring masses range from 0.6 to 16 M⊕that are systematically lower than those inferred in the younger HL Tau disk.The arc occupies nearly 20%of the total dust mass.Such a high mass fraction of dust grains concentrated in a local region is consistent with the mechanism of dust trapping into vortices.Assuming a gas-to-dust mass ratio of 30 that is constant throughout the disk,the dense and cold arc is close to the threshold of being gravitationally unstable,with the Toomre parameter Q∼1.3.Nevertheless,our estimate of Q relies on the assumption for the unknown gas-to-dust mass ratio.Adopting a lower gas-to-dust mass ratio would increase the inferred Q value.Follow-up high resolution observations of dust and gas lines are needed to clarify the origin of the substructures.