星系中磁场的演化和未来的平方公里阵列观测试验
Evolution of magnetic fields in galaxies and future observational tests with the Square Kilometre Array
摘要：
目标。本文根据现有的星系形成和演化模型，研究了星系中大小尺度磁场的宇宙学演化。方法.我们用发电机理论导出了盘星系和膨胀星系中磁场的放大和有序化的时间尺度。原星系晕中由热维里化产生的湍流可以驱动一个有效的湍流发电机。层次结构形成宇宙学的模拟结果提供了一个工具，以发展一个演化模型的规则磁场耦合星系形成和演化。结果湍流（小尺度）发电机能够在几个10^8年内将原星系晕中的微弱种子磁场放大到几μ G的强度。这个湍流场是平均场（大尺度）发电机的种子。类似于银河系的星系在z~10处形成了它们的圆盘，并且在2 Gyr（z~3处）内产生了muG强度和几kpc相干长度的规则场，但是在星系大小的相干尺度上的场排序需要额外的6 Gyr（z~0.5处）。巨大的星系在z~10时形成了它们的盘，这使得在z~4时就能更有效地产生强规则场（相干长度为kpc）。然而，宇宙的年龄对于大于15 kpc的巨大星系中的完全相干场来说是短暂的。矮星系应该在z~1处拥有完全相干的场。在一次主要的合并之后，湍流场的强度增强了几倍。结论.这种进化的情况下，可以测试偏振同步辐射和法拉第旋转与计划SKA的测量。我们预言星系大小与有序尺度和星系大小之比之间存在着一个近似的关系。
英文摘要：
Aims. We investigate the cosmological evolution of large- and small-scale magnetic fields in galaxies in the light of present models of formation and evolution of galaxies. Methods. We use the dynamo theory to derive the timescales of amplification and ordering of magnetic fields in disk and puffy galaxies. Turbulence in protogalactic halos generated by thermal virialization can drive an efficient turbulent dynamo. Results from simulations of hierarchical structure formation cosmology provide a tool to develop an evolutionary model of regular magnetic fields coupled with galaxy formation and evolution. Results. The turbulent (small-scale) dynamo was able to amplify a weak seed magnetic field in halos of protogalaxies to a few muG strength within a few 10^8 yr. This turbulent field served as a seed to the mean-field (large-scale) dynamo. Galaxies similar to the Milky Way formed their disks at z~10 and regular fields of muG strength and a few kpc coherence length were generated within 2 Gyr (at z~3), but field-ordering on the coherence scale of the galaxy size required an additional 6 Gyr (at z~0.5). Giant galaxies formed their disks at z~10, allowing more efficient dynamo generation of strong regular fields (with kpc coherence length) already at z~4. However, the age of the Universe is short for fully coherent fields in giant galaxies larger than 15 kpc to have been achieved. Dwarf galaxies should have hosted fully coherent fields at z~1. After a major merger, the strength of the turbulent field is enhanced by a factor of a few. Conclusions. This evolutionary scenario can be tested by measurements of polarized synchrotron emission and Faraday rotation with the planned SKA. We predict an anticorrelation between galaxy size and ratio between ordering scale and galaxy size (abridged).
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
