Effects of Ohmic and ambipolar diffusion on formation and evolution of first cores, protostars, and circumstellar discs
Abstract
We investigate the formation and evolution of a first core, protostar, and circumstellar disc with a three-dimensional non-ideal (including both Ohmic and ambipolar diffusion) radiation magnetohydrodynamics simulation. We found that the magnetic flux is largely removed by magnetic diffusion in the first-core phase and that the plasma β of the centre of the first core becomes large, β > 104. Thus, proper treatment of first-core phase is crucial in investigating the formation of protostar and disc. On the other hand, in an ideal simulation, β ∼ 10 at the centre of the first core. The simulations with magnetic diffusion show that the circumstellar disc forms at almost the same time of protostar formation even with a relatively strong initial magnetic field (the value for the initial mass-to-flux ratio of the cloud core relative to the critical value is μ = 4). The disc has a radius of r ∼ 1 AU at the protostar formation epoch. We confirm that the disc is rotationally supported. We also show that the disc is massive (Q ∼ 1) and that gravitational instability may play an important role in the subsequent disc evolution.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- September 2015
- DOI:
- 10.1093/mnras/stv1290
- arXiv:
- arXiv:1503.04901
- Bibcode:
- 2015MNRAS.452..278T
- Keywords:
-
- MHD;
- methods: numerical;
- protoplanetary discs;
- stars: formation;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 13 pages, 11 figures, accepted for publication in MNRAS