Hidden spiral structure in the dust continuum emission of the Protostellar disk around IRAS 16544-1604 in CB 68

Sanemichi Takahashi  (NAOJ/Kagoshima University)

Investigation of the physical structure of protostellar disks is necessary for understanding the subsequent disk evolution and planet formation. We have performed numerical simulations with radiative transfer calculations to model the protostellar disk around the Class 0 protostar, IRAS 16544-1604 in CB 68. This source is one of the eDisk targets and exhibits a shoulder feature in the dust continuum emission along the major axis.

Numerical simulations of star and disk formation processes predict that young disks can be massive enough to form a spiral structure due to gravitational instability. Our observational simulations of gravitationally unstable disk models show that spiral arms become less discernible when the disk is inclined and convolved with the telescope beam. This means that the absence of the spiral features in the eDisk observations does not necessarily indicate that the disk is gravitationally stable.  We also found that the asymmetric shoulder structure of the continuum profile along the major axis appears when the disk has the asymmetric spiral structure or the disk is massive enough with a Toomre parameter Q~1. This mechanism provides a possible explanation for the observed intensity profile of the disk surrounding IRAS 16544.