Outflows and mass accretion in collapsing dense cores with misaligned rotation axis and magnetic field

Abstract

Outflows and jets are intimately related to the formation of stars, and play an important role in redistributing mass, energy and angular momentum within the dense core and parent cloud. The interplay between magnetic field and rotation is responsible for launching these outflows, whose formation has been generally carried out for idealized systems where the angle $\alpha$ between the rotation axis and large-scale magnetic field is zero. Here we explore, through three-dimensional ideal magneto-hydrodynamic simulations, the effects of a non-zero $\alpha$ on the formation of outflows during the collapse of dense pre-stellar cores. We find that mass ejection is less efficient for increasing angle $\alpha$, and that outflows are essentially suppressed for $\alpha\sim90^{\circ}$. An important consequence is a corresponding increase of the mass accreted onto the adiabatic (first) core. In addition, mean flow velocities tend to increase with $\alpha$, and misaligned configurations produce clumpy, heterogeneous outflows that undergo precession, and are more prone to instabilities.Comment: Accepted for publication in MNRAS letters, 6 pages 4 figure