Using numerical simulations of magnetized stellar winds, we carry out a parameter study to find the dependence of the stellar wind torque on observable parameters. We find that the power-law dependencies of the torque on parameters is significantly d
ifferent than what has been used in all spin evolution models to date.
Astrophysical jets are associated with the formation of young stars of all masses, stellar and massive black holes, and perhaps even with the formation of massive planets. Their role in the formation of planets, stars, and galaxies is increasingly ap
preciated and probably reflects a deep connection between the accretion flows - by which stars and black holes may be formed - and the efficiency by which magnetic torques can remove angular momentum from such flows. We compare the properties and physics of jets in both non-relativistic and relativistic systems and trace, by means of theoretical argument and numerical simulations, the physical connections between these different phenomena. We discuss the properties of jets from young stars and black holes, give some basic theoretical results that underpin the origin of jets in these systems, and then show results of recent simulations on jet production in collapsing star-forming cores as well as from jets around rotating Kerr black holes.
We present results from our numerical simulations of collapsing massive molecular cloud cores. These numerical calculations show that massive stars assemble quickly with mass accretion rates exceeding 10^-3 Msol/yr and confirm that the mass accretion
during the collapsing phase is much more efficient than predicted by selfsimilar collapse solutions, dM/dt ~ c^3/G. We find that during protostellar assembly out of a non-turbulent core, the mass accretion reaches 20 - 100 c^3/G. Furthermore, we explore the self-consistent structure of bipolar outflows that are produced in our three dimensional magnetized collapse simulations. These outflows produce cavities out of which radiation pressure can be released, thereby reducing the limitations on the final mass of massive stars formed by gravitational collapse. Additional enhancement of the mass accretion rate comes from accretion along filaments that are built up by supersonic turbulent motions. Our numerical calculations of collapsing turbulent cores result in mass accretion rates as high as 10^-2 Msol/yr.
