مشخصات پژوهش

The core-envelope separation during the gravitational collapse is one of the important mechanisms in the binary formation that may occur in a rotating filamentary cloud. In this study, we consider the self-similar dynamic collapse of a rotating filament, including the effect of magnetic braking and ambipolar diffusion in the intermediate and surrounding mediums (or envelope) of the cloud. The self-similar dynamic formalism is used in the nonideal magnetohydrodynamic regime to study the gravitational collapse. We divide our study into two parts, i.e., isothermal configuration and polytropic configuration. The problem in the isothermal configuration is solvable as a function of the independent self-similar variable. This analytical result can give us a new perspective on the isothermal collapse. The results in the polytropic configuration can be obtained by numerical methods. The presence of ambipolar diffusion results in a toroidal component of magnetic field during the self-similar collapse in these mediums, which markedly affects the magnetic braking. In fact, this braking effect in the toroidal direction causes a rotation opposite to the initial rotation, which may lead to the core-envelope separation. We also found that the ratio of magnetic pressure to gas pressure, which is a resistive criterion versus the gravity force, decreases by increasing the ambipolar diffusion coefficient. Finally, the results point to regions of interest in which the coreenvelope separation may be seen.