Two-dimensional angular momentum distribution toward protostellar cores
In star formation at the early phase, angular momentum distribution of a natal core is crucial to determine the evolution of the core such as binary formation and disk formation. We have not yet fully understood the angular momentum distribution of such dense cores. We introduced a new method to calculate the two-dimensional specific angular momentum distribution of a core and derived the direction of the rotation axis of a dense core in L1527 as a function of the core radius. In the present study, we applied our method to dense cores toward, B335 and L1551 with the Nobeyama 45m telescope. Our method could derive the direction of the rotation axis as a function of the core radius. In the dense core L1527, we found that the direction of the angular momentum vector changes from outside to inside and thus, we have confirmed that the dense core L1527 cannot be described by a single rotation axis. On the other hand, the dense core B335 has almost a single direction of the vector and thus, we have suggested that B335 has evolved from a core with a rigid rotation. Since the inner rotational axis direction is especially important for formation and evolution of the inner rotating disk, we consider that analysis of the two dimensional specific angular momentum distributions is required. Our method has advantages over the similar analysis of dense cores in the previous studies. First the linear or planar fitting of the line of sight velocity to derive a velocity gradient cannot detect change of the rotational axis (Goodman+1993, Ohashi+1997, and Caselli+2002). Second the position-velocity diagrams can distinguish between rigid-rotation or differential rotation of the core, but only the cut direction. (Belloch+2002).