Shih-Ping Lai

(National Tsing Hua University)

Planets form in disks around their host protostars, but when and how disks form is still largely unanswered.  With ALMA Cycle 0 data, we have found an extremely young proto-planetary disk around VLA1623A still in the earliest star formation stage (Class 0).   Our analysis of C18O in the disk revealed its motion to be Keplerian and to have a radius of at least 5 times the radius of Neptune’s orbit (~150AU), but with a central protostellar mass of only 0.2 times our Sun’s mass.   Such rotationally supported disks were commonly found in later stages of star formation, but only a handful of them being found at Class 0 stage (Murillo et al. 2013).  Models and simulations have previously predicted that Keplerian disks cannot form in the earliest phases of star formation. However, the discovery of VLA1623A’s big Keplerian disk proves otherwise, suggesting that other factors may play a role in disk formation.  This is in line with more recent studies that suggest that misalignment of magnetic field and rotation axes or turbulence may enhance early disk formation, producing disks of 100 times the Earth-Sun radius or larger.  In order to advance our knowledge of planet formation, we would like to use the ALMA data archive to search for more proto-planetary disks and investigate the environment where proto-planetary disks are formed.