Fragmentation of filamentary molecular clouds with longitudinal magnetic fields: Formation of disks and their collapse

We followed the fragmentation of magnetized filamentary clouds and the formation of disks with numerical simulations and a semianalytical approach. Two-dimensional magnetohydrodynamical simulations showed that a filamentary cloud with longitudinal magnetic fields fragments to form gemoetrically thin disks perpendicular to the magnetic field. Each disk contracts dynamically toward the symmetry axis keeping quasi-static equilibrium in the direction parallel to the axis. We followed the late-stage evolution of the disk with a one-dimensional numerical simulation assuming that the disk is infitesimally thin and found that hte disk approaches a state in which the surface density is inversely proportional to the distance from the center, suggesting the existence of a similarity solution. With some simplification we obtaine numerically some similarity solutions for one-dimensional dynamically contracting disks.