EPoS Contribution
EPoS Contribution
Size estimation of disks around proto-stars, from boundary conditions in collapsing dense cores

Erick Nagel
Centro de Radioastronomia y Astrofisica, Morelia, Mexico
Disk and star formation are closely related issues, because both processes occur at the same time. The disk and star are formed from collapsing dense cores, however, angular momentum conservation requires that the core's material is rotating. It is common to relate the size of the disk to the largest Keplerian orbit, using the largest specific angular momentum of the cloud from which the disk forms. However, a new ballistic stationary solution of the collapse of material falling towards a point mass object, predicts that besides the angular momentum, the radial velocity at the boundary of the ballistic region is required to estimate the size of the disk. This is important in the embedded stage, when material is still falling into the star-disk system; in other words, the size of the disk is given by the characteristics of the collapsing particles and not by the subsequent evolution towards an equilibrium configuration. The solution is very useful because one can choose the relevant boundary conditions of the region that is collapsing. This cannot be done with another solution, which is commonly used by many workers. For both solutions, the boundary is rigidly rotating. The solution is applied to some realistic cases. The boundary conditions are consistently extracted from: shocks by stellar winds, supernova explosions and radiatively driven implosions due to the radiation of recently formed stars in potential sites of star formation. The differences between such mechanisms in the size of the resulting disks is presented.