ALMA 2D Super-resolution Survey of Ophiuchus Class I/Flat/II Disks: Discovery of New Substructure and Implications for Disk Evolution

ABSTRACT :
Recent high-resolution ALMA observations of protoplanetary disks revealed unique substructures and suggested that substructures rapidly evolve from Class I to II. Clarifying when substructures form enables us to know the initial environments of planet formation. We focus on Class I/Flat/II disks in Ophiuchus molecular cloud, an active star-forming region, to grasp signs of substructure formation in the accretion phase. We employ 2D super-resolution imaging based on Sparse Modeling for the archival ALMA Band6 continuum data. As a result, we have obtained images with spatial resolutions comparable to a few au (0”.02-0”.2) for 67 dust disks resolved spatially and confirmed new substructures of 18 disks (5 Class I, 7 Class Flat and 6 Class II disks). We also see the separated two peaks in the distribution of inclination angles for Class I and Flat disks. It indicates that nearly edge-on disks may look younger than they are. Further observations of envelope and/or outflow around Class I/Flat disks are critical to determining whether substructure and planet formation begin in the accretion phase.