2021ApJ...923..121Y

Based on Atacama Large Millimeter/submillimeter Array (ALMA) observations, compact protoplanetary disks with dust radii of r <= 20-40 au were found to be dominant in nearby low-mass star formation regions. However, their substructures have not been investigated because of the limited spatial resolution achieved so far. We apply a newly developed super-resolution imaging technique utilizing sparse modeling (SpM) to explore several au-scale structures in such compact disks. SpM imaging can directly solve for the incomplete sampling of visibilities in the spatial frequency and potentially improve the fidelity and effective spatial resolution of ALMA images. Here we present the results of the application to the T Tau system. We use the ALMA 1.3 mm continuum data and achieve an effective spatial resolution of ∼30% (5 au) compared with the conventional CLEAN beam size at a resolution of 17 au. The reconstructed image reveals a new annular gap structure at r = 12 au in the T Tau N compact disk, with a dust radius of 24 au, and resolves the T Tau Sa and Sb binary into two sources. If the observed gap structure in the T Tau N disk is caused by an embedded planet, we estimate a Saturn-mass planet when the viscous parameter of the disk is 10^–3. Ultimately, ALMA observations with enough angular resolution and sensitivity should be able to verify the consistency of the super-resolution imaging and definitely confirm the existence of this disk substructure.