Effects of Ohmic and ambipolar diffusion on formation and evolution of first cores, protostars, and circumstellar discs
Effects of Ohmic and ambipolar diffusion on formation and evolution of first cores, protostars, and circumstellar discs
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DOI：
10.1093/mnras/stv1290
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发表时间：
2015-03
影响因子：
4.8
通讯作者：
Y. Tsukamoto;K. Iwasaki;S. Okuzumi;M. Machida;S. Inutsuka
中科院分区：
文献类型：
--
作者：
Y. Tsukamoto;K. Iwasaki;S. Okuzumi;M. Machida;S. Inutsuka
我们通过三维非理想（包括欧姆和双极扩散）辐射磁流体动力学模拟研究了第一个核心、原恒星和星周盘的形成和演化。我们发现，第一核心相中的磁通量很大程度上被磁扩散消除，并且第一核心中心的等离子体$\beta$变大，$\beta>10^4$。因此，正确处理第一核心相对于研究原恒星和盘的形成至关重要。另一方面，在理想的模拟中，$\beta\sim 10$ 位于第一个核心的中心。磁扩散模拟表明，即使初始磁场相对较强（云核初始质量通量比相对于临界值$\mu=4$），星周盘几乎与原恒星形成同时形成。在原恒星形成时期，圆盘的半径为 $r \sim 1$ AU。我们确认光盘受到旋转支撑。我们还表明，该盘是巨大的（$Q\sim 1$），并且重力不稳定可能在随后的盘演化中发挥重要作用。
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 $\beta$ of the centre of the first core becomes large, $\beta>10^4$. 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, $\beta\sim 10$ 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 $\mu=4$). The disc has a radius of $r \sim 1$ AU at the protostar formation epoch. We confirm that the disc is rotationally supported. We also show that the disc is massive ($Q\sim 1$) and that gravitational instability may play an important role in the subsequent disc evolution.