Generation of the primordial magnetic fields during cosmological reionization
Generation of the primordial magnetic fields during cosmological reionization
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DOI：
10.1086/309272
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发表时间：
2000-08-20
影响因子：
4.9
通讯作者：
Zweibel, EG
中科院分区：
文献类型：
--
作者：
Gnedin, NY;Ferrara, A;Zweibel, EG
我们使用原星系中恒星对宇宙再电离的新模拟，研究了比尔曼电池在宇宙电离前沿产生的磁场。两种机制主要负责磁发生：(1)电离锋从原星系爆发和(2)电离锋通过高密度中性细丝传播，这是宇宙网的一部分。在电离区重叠(z约为7)之前，第一种机制占主导地位，而第二种机制即使在那个时代之后仍继续运行。然而，叠加后场强的增加在很大程度上是由于宇宙结构形成时发生的气体压缩。因此，z约为5时的磁场与气体密度密切相关，并且在兆秒尺度上是高度有序的。在模拟框中，平均质量加权场强B-0近似为10(-19)G。在我们的模拟中，B-0和维里化天体的重子质量之间有一个相对明确的、近乎线性的关联，在最大质量的天体(M接近10(9)M)中，B-0近似为10(-18)G。这是一个下限，因为缺乏数值分辨率使我们无法跟踪可能放大原星系磁场的小尺度动力学过程。尽管我们计算的持有强度可能足以作为银河系发电机的种子场，但这个场太小了，不足以对星系的形成、热传导或星系间介质中的宇宙射线传输产生重大影响。然而，通过基于伽马射线爆发光子到达时间分析的创新方法，可以在星系间介质中观察到它。
We investigate the generation of magnetic fields by the Biermann battery in cosmological ionization fronts, using new simulations of the reionization of the universe by stars in protogalaxies. Two mechanisms are primarily responsible for magnetogenesis: (1) the breakout of ionization fronts from protogalaxies and (2) the propagation of ionization fronts through the high-density neutral filaments that are part of the cosmic web. The first mechanism is dominant prior to overlapping of ionized regions (z approximate to 7), whereas the second continues to operate even after that epoch. However, after overlap the field strength increase is largely due to the gas compression occurring as cosmic structures form. As a consequence, the magnetic field at z approximate to 5 closely traces the gas density, and it is highly ordered on megaparsec scales. The mean mass-weighted field strength is B-0 approximate to 10(-19) G in the simulation box. There is a relatively well-defined, nearly linear correlation between B-0 and the baryonic mass of virialized objects, with B-0 approximate to 10(-18) G in the most massive objects (M approximate to 10(9) M,) in our simulations. This is a lower limit, as lack of numerical resolution prevents us from following small-scale dynamical processes that could amplify the field in protogalaxies. Although the held strengths we compute are probably adequate as seed fields for a galactic dynamo, the field is too small to have had significant effects on galaxy formation, on thermal conduction, or on cosmic-ray transport in the intergalactic medium. It could, however, be observed in the intergalactic medium through innovative methods based on analysis of gamma-ray burst photon arrival times.