极端原初暗晕中的磁场：湍流转坍及其对早期类星体形成的启示
Magnetic fields in extreme primordial halos: turbulent collapse and implications for early quasar formation
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中文总结 AI 辅助
本研究通过宇宙学高分辨率磁流体动力学模拟，探究极端原初暗晕的磁场演化，发现其由大尺度动力学主导，即使有磁场仍会形成约10^4倍太阳质量的中心大质量天体。
中文摘要 AI 辅助
有人提出，高红移处质量最大的类星体可能形成于宇宙密度场中罕见的高σ峰值。我们利用初始场强为$10^{-14}-10^{-8}$G的宇宙学高分辨率磁流体动力学变焦模拟，研究了对应于这些罕见σ峰值之一的大质量原初暗晕的演化。该暗晕形成于强会聚流的交汇处，已在星系际尺度上形成了高度超声速湍流，暗晕内部的湍流马赫数约为10-20。湍流磁场放大效应此前从未在该 regime 中被研究过，因此我们探究这是否会产生与更典型暗晕中观测到的类似效应。较弱的初始场因剪切流作用被放大得稍强，但不同模拟中的整体演化相当相似，且流场由超声速湍流主导。我们特别表明，湍流金斯质量始终主导热金斯质量和磁金斯质量，仅在$10^{-2}-10$pc的尺度上，磁金斯质量才可能与热金斯质量相当。因此，我们的模拟强烈表明演化由大尺度动力学主导。如先前研究确立的，我们因此预期，即使存在磁场，也会形成质量约为$10^4$倍太阳质量的中心大质量天体。这种情况与更典型的原子冷却暗晕略有不同，先前结果表明，在中间尺度上磁金斯质量的相关性更大，可能会增大大质量天体的质量。
英文摘要
It is sometimes suggested that the most massive quasars at high redshift may have formed from rare high-sigma peaks in the cosmic density field. We explore here the evolution in a massive primordial halo corresponding to one of these rare sigma peaks, employing cosmological high-resolution magneto-hydrodynamical zoom-in simulations with initial field strength of $10^{-14}-10^{-8}$ G. The dark matter halo forms at the intersection of strongly convergent flows, leading to the formation of highly supersonic turbulence already on intergalactic scales, with turbulent Mach numbers of order $10-20$ also within the halo. Turbulent magnetic field amplification has never been explored in this regime and we therefore investigate whether this gives rise to effects similar to those observed in more typical halos. While the weaker initial field is somewhat more strongly amplified as a result of the shear flows, overall the evolution in the different simulations is rather similar and the flows are dominated by supersonic turbulence. We show in particular that the turbulent Jeans mass always dominates over the thermal and magnetic Jeans masses, and only on scales of $10^{-2}-10$ pc, the magnetic Jeans mass may become comparable to the thermal one. Our simulations thus strongly suggest the evolution to be dominated by the large-scale dynamics. As established in previous work, we thus expect the formation of central massive objects of a few times $10^4$ M$_\odot$ also in the presence of magnetic fields. The situation is somewhat different from more typical atomic cooling halos, where previous results have indicated a larger relevance of the magnetic Jeans mass on intermediate scales, potentially enhancing the mass of the massive object.
