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arXiv 2005.10269astro-ph.GAastro-ph.CO
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原始磁场如何使星系收缩

How primordial magnetic fields shrink galaxies

Sergio Martin-Alvarez, Adrianne Slyz, Julien Devriendt, Carlos Gómez-Guijarro

摘要:

作为星际介质能量收支的主要贡献者之一,磁场自然在塑造星系演化中发挥作用。银河系的磁场可以起源于强大的原始磁场,只要这些磁场保持在当前观测的上限之下。为了了解这样的磁场将如何影响星系的全球形态和动力学特性,我们使用一套高分辨率的约束运输磁流体动力学宇宙学变焦模拟,我们改变初始磁场强度和配置以及处方恒星反馈。我们发现,强大的原始磁场延迟了恒星形成的开始,耗尽了星系的旋转支持,减少了星系盘的径向尺寸,并向中心驱动了更多的气体。这也反映在模拟UVJ观测中,即星系光剖面浓度的增加。我们探讨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被放大的恒星反馈的存在下,我们简要地讨论了我们测量的变化是否也将预期为银河系磁场的非原始起源。

英文摘要:

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.

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