论文标题
指数放大的磁场消除了种群iii原恒星周围的磁盘碎片化
Exponentially amplified magnetic field eliminates disk fragmentation around the Population III protostar
论文作者
论文摘要
一个关键的问题是不清楚第一颗（种群III）恒星的初始质量功能是积聚磁盘中形成的次级原恒星的最终命运，特别是它们是合并还是生存。我们专注于宇宙学磁场下第一颗恒星形成的磁效应。我们进行一套理想的磁流失动力模拟，直到第一个原恒星形成后的1000年。我们采用了状态方法的刚性方程来代表代表连接到Protostar的磁场结构的刚性方程。在云中首次使用$ b_0 = 10^{ - 20} $ g初始化的云中的第一个原始的构建$ n_0 = 10^4 \，{\ rm cm^{ - 3}} $在云初始初始化的十年后，protostar周围的磁场强度从pico-toco-gauss到kilo-gauss，这是相同的强度，这与现在的日子相同。自Protostar附近的气体（$ \ leq \！10 $ au）中，磁场迅速结束。随着质量积聚的进展，重要的磁场区域向外延伸，磁制动消除了在未经磁模型中形成的磁盘的碎片化。另一方面，假设具有小角度动量的气云，这种扩增可能不起作用，因为旋转会较慢。但是，在这种情况下不会发生磁盘破碎。我们得出的结论是，宇宙学磁场强度的指数扩增约为$ 10^{ - 18} $ g，消除了种群III质体周围的磁盘碎片。
One critical remaining issue to unclear the initial mass function of the first (Population III) stars is the final fate of secondary protostars formed in the accretion disk, specifically whether they merge or survive. We focus on the magnetic effects on the first star formation under the cosmological magnetic field. We perform a suite of ideal magnetohydrodynamic simulations until 1000 years after the first protostar formation. Instead of the sink particle technique, we employ a stiff equation of state approach to represent the magnetic field structure connecting to protostars. Ten years after the first protostar formation in the cloud initialized with $B_0 = 10^{-20}$ G at $n_0 = 10^4\,{\rm cm^{-3}}$, the magnetic field strength around protostars amplifies from pico- to kilo-gauss, which is the same strength as the present-day star. The magnetic field rapidly winds up since the gas in the vicinity of the protostar ($\leq\!10$ au) has undergone several tens orbital rotations in the first decade after protostar formation. As the mass accretion progresses, the vital magnetic field region extends outward, and the magnetic braking eliminates fragmentation of the disk that would form in the unmagnetized model. On the other hand, assuming a gas cloud with small angular momentum, this amplification might not work because the rotation would be slower. However, disk fragmentation would not occur in that case. We conclude that the exponential amplification of the cosmological magnetic field strength, about $10^{-18}$ G, eliminates disk fragmentation around the Population III protostars.
