EPoS Contribution
EPoS Contribution
Anisotropic and episodic accretion onto protostellar disks

Daniel Seifried
Hamburg Observatory, Hamburg, DE
We present new results of numerical simulations on the question of how Class 0 stage protostellar disks gain their mass and angular momentum in turbulent molecular cloud cores. Considering a wide range of realistic initial conditions for star forming regions we simulate the collapse of molecular cloud cores and the subsequent the formation and evolution of protostellar disks. One of the key results is the highly anisotropic accretion flow of mass and angular momentum towards the protostellar disk. A detailed analysis of the accretion flow in these turbulent environments reveals that accretion preferentially occurs along a few, very narrow accretion channels. These accretion channels usually cover only about 10% of the surface area, despite the fact that the bulge of accretion occurs along them. Along with this turbulent accretion flow comes a strongly disordered magnetic field in the surroundings of the disk. By measuring the number of magnetic field reversals, we can show that the magnetic field has a highly complex structure up to scales of 1000 AU. We discuss how the anisotropic accretion mode and the disordered magnetic field structure allow for the formation of rotationally supported disks in the Class 0 stage in a natural way. Beside the anisotropy, the accretion flow onto the protostellar disk reveals a high time variability. We discuss this effect and how it subsequently leads to an episodic mass accretion onto the protostar itself, which would have significant effects on the radiation released by the protostars.
Caption: Left: Accretion flow (volume rendering and vector field) towards a protostellar disk (blue contours) on scales of 1000 AU. Accretion occurs in a highyl anisotropic fashion along several narrow channels. The magnetic field (black lines) is highly disordered. Right: Hammer projection of the accretion flow as seen from the disk's center (blue: gas flow towards the disk, red: gas flow away from the disk). The different accretion channels seen in the right image clearly show up in the projection.
Collaborators:
R. Banerjee, Hamburg Observatory., Germany
R. Klessen, ITA Heidelberg, Germany
R. Pudritz, McMaster U., Canada
Key publication

Suggested Sessions: Cores to Disks