title: Simultaneous Growth of a Protostar and a Young Circumstellar Disk in the Early Phase of Disk Formation

authors: Takuya Ohtani and Toru Tsuribe

abstract: Protoplanetary disks are the birthplace of planets. The appropriate model for the formation and the evolution of the disk is desirable. In this workshop, we will present the simultaneous growth model of both the protostar and the circumstellar disk. We study the origin of surface density distribution and the disk to star mass ratio by numerically solving unsteady evolution of one-dimensional axisymmetric model for viscous accretion disk. We find that the radial profile of surface density of the disk approaches the "quasi-steady state". This state is determined mainly by the process of angular momentum transport rather than the original distribution of angular momentum of the cloud core. We also find that the disk mass tends to be larger than the star mass as long as the constant dynamical flow onto the disk is assumed. Finally, we will show the P-V diagram of the disk in our model to compare to the observations of the star-forming region.