As one of the prime contributors to the interstellar medium energy budget, magnetic fields naturally play a part in shaping the evolution of galaxies. Galactic magnetic fields can originate from strong primordial magnetic fields provided these latter remain below current observational upper limits. To understand how such magnetic fields would affect the global morphological and dynamical properties of galaxies, we use a suite of high-resolution constrained transport magneto-hydrodynamic cosmological zoom simulations where we vary the initial magnetic field strength and configuration along with the prescription for stellar feedback. We find that strong primordial magnetic fields delay the onset of star formation and drain the rotational support of the galaxy, diminishing the radial size of the galactic disk and driving a higher amount of gas towards the centre. This is also reflected in mock UVJ observations by an increase in the light profile concentration of the galaxy. We explore the possible mechanisms behind such a reduction in angular momentum, focusing on magnetic braking. Finally, noticing that the effects of primordial magnetic fields are amplified in the presence of stellar feedback, we briefly discuss whether the changes we measure would also be expected for galactic magnetic fields of non-primordial origin.

中文翻译：

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原始磁场如何缩小星系

作为星际介质能量收支的主要贡献者之一，磁场自然会在塑造星系演化过程中发挥作用。银河磁场可以源自强大的原始磁场，前提是这些原始磁场保持在当前的观测上限以下。为了了解这种磁场将如何影响星系的全局形态和动力学特性，我们使用了一套高分辨率约束输运磁流体动力学宇宙学缩放模拟，其中我们改变了初始磁场强度和配置以及恒星反馈的处方. 我们发现强大的原始磁场延迟了恒星形成的开始并消耗了星系的旋转支持，减小银盘的径向尺寸，并将更多的气体推向中心。这也反映在模拟 UVJ 观测中，增加了星系的光分布浓度。我们探索了这种角动量减少背后的可能机制，重点是磁制动。最后，注意到原始磁场的影响在恒星反馈的存在下被放大，我们简要讨论了我们测量的变化是否也适用于非原始起源的星系磁场。