FRAGMENTATION OF ELONGATED CYLINDRICAL CLOUDS

Using 3D hydrodynamical simulations, we study the fragmentation of uni form, isothermal, elongated molecular clouds, which are slowly rotatin g around an axis perpendicular to their elongation. We argue that this process could result in the formation of binary and multiple stars. T his new method for forming binary stars can explain widely separated b inaries with large eccentricities and various mass ratios. At relative ly low Jeans numbers J0 (the ratio of the binding energies to thermal energies), a simple binary system is formed. For higher J0, multiple f ragmentation occurs between the binary fragments, forming a multiple s ystem. This spontaneous additional fragmentation is induced by rotatio n. The addition of an angular momentum component parallel to the axis of elongation complicates this scenario. At low J0, a simple binary is still formed. At higher J0, multiple fragmentation no longer occurs b etween the binary fragments but instead the binary fragments themselve s can fragment through an intermediary bar stage, or through an interm ediary fragment-disk stage.