On Magnetohydrodynamic Jet Production in the Collapsing and Rotating Envelope

We present results from axisymmetric, time-dependent hydrodynamical (HD) andmagnetohydrodynamical (MHD) simulations of a gaseous envelope collapsing onto ablack hole (BH). We consider gas with so small angular momentum that after aninitial transient, the flow in the HD case, accretes directly onto a BH withoutforming a rotationally support torus. However, in the MHD case even with a veryweak initial magnetic field, the flow settles into a configuration with fourcomponents: (i) an equatorial inflow, (ii) a bipolar outflow, (iii) polarfunnel outflow, and (iv) polar funnel inflow. We focus our analysis on thesecond flow component of the MHD flow which represents a simple yet robustexample of a well-organized inflow/outflow solution to the problem of MHD jetformation. The jet is heavy, highly magnetized, and driven by magnetic andcentrifugal forces. A significant fraction of the total energy in the jet iscarried out by a large scale magnetic field. We review previous simulations,where specific angular momentum was higher than that assumed here, and concludethat our bipolar outflow develops for a wide range of the properties of theflow near the equator and near the poles. Future work on such a simpleinflow/outflow solution will help to pinpoint the key elements of realjets/outflows as well as help to interpret much more complex simulations aimedat studying jet formation and collapse of magnetized envelopes.Comment: to appear in ApJ, revised version with new HD result