演講資訊

摘要：

Circumstellar disks are ubiquitous around young stellar objects and are considered to be the sites of planet formation. How these disks form during the processes of star formation is not well understood. Conventionally, formation of a disk in a collapsing dense core is expected as a consequence of angular momentum conservation. Later theoretical studies of collapsing dense cores incorporating magnetic field suggest that the magnetic field can slow down gas motions and suppress disk formation. However, such effects have not yet been observationally confirmed or constrained. In this presentation, I will introduce our observational results of gas motions around a sample of protostars obtained with single dishes, SMA, and ALMA. With these observations, we have found evolution of gas motions toward Keplerian rotation and transitional regions from collapsing cores to disks, i.e., signs of disk formation in the early stage of star formation. Opposite to this, we have also found few protostars where disk formation can be suppressed. I will discuss these results in the context of disk formation with and without magnetic field.