Early Planet Formation in Embedded Disks (eDisk): Highlight of representative first-look results

Nagayoshi Ohashi^1*, John J. Tobin², Jes K. Jørgensen³, eDisk collaboration⁴

¹Institute of Astronomy & Astrophysics, Academia Sinica, Taipei, Taiwan
²National Radio Astronomy Observatory, Charlottesville, USA
³Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
⁴eDisk collaboration, Taiwan

* Presenter:Nagayoshi Ohashi, email:ohashi@asiaa.sinica.edu.tw

Disks around young stellar objects (YSOs) are considered to be the site of planet formation. Recent observations at high angular resolutions have revealed that substructures, such as rings and gaps, are ubiquitous in protoplanetary disks around Class II YSOs, raising a possibility that at least some planet formation may have already started in disks around protostars during the embedded stages of star formation. In order to address exactly how and when planet formation is initiated, we have conducted the Large Program, “Early Planet Formation in Embedded Disks (eDisk)” using the Atacama Millimeter and submillimeter Array (ALMA), aiming to search for substructures in disks around 12 Class 0 and 7 Class I protostars in nearby (d < 200 pc) star forming regions through 1.3 mm continuum observations at a resolution of ~0.04” (~7 au). The initial results show that the continuum emission, mostly arising from dust disks around the observed protostars, has relatively less distinctive substructures in marked contrast to disks around Class II YSOs. The continuum emission, on the other hand, often shows brightness asymmetry particularly along the minor axis of its elongation, suggesting flared dust disk structures around protostars in another marked contrast to Class II disks. These dramatic differences may suggest that dust grains in disks quickly settle down onto their middle planes and quickly form substructures when protostars evolve into Class II YSOs. The program has also observed molecular lines, such as CO isotopologues, providing kinematical information to identify Keplerian disks around the observed protostars and to estimate dynamical masses of the protostars. While preliminary results of the eDisk program were reported in the annual meeting of the Physical Society of Taiwan in 2022, latest results based on completed observations will be reported in this meeting.

Keywords: star and planet formation , protostars, protoplanetary disks, embedded disks