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arXiv 1811.04401astro-ph.GA
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磁场在星系演化中的作用

The Role of Magnetic Fields in The Evolution of Galaxies

Fatemeh S. Tabatabaei

摘要:

磁场构成了星系中星际介质的能量成分,因此可以影响星系结构的形成。对星系样品进行了灵敏的分辨射电连续谱观测和统计研究,以研究磁场的起源和影响。JVLA对本星系群M33的云尺度观测揭示了沿着旋臂和星系中心的强烈纠缠磁场,这表明由于分子云的压缩和局部剪切而产生的放大。通过对一个非星系团、无相互作用的星系样本的研究,我们发现大尺度有序磁场与星系的自转速度成比例关系。在正常的恒星形成星系中,总的和无序的磁场与恒星形成速率成比例。另一方面,NGC 1097中心的一个强大的磁场--一个正在淬火的大质量星系--被发现是减缓其大质量恒星形成的原因。综合这些结果,我们可以推断:1)在大爆炸后大约1 Gyr的大质量恒星诞生高峰之后不久,宇宙就被高度磁化了; 2)在这段时间之后,强磁场可能起到了反反应的作用,淬灭了大质量恒星的形成,并刺激了大质量星系中低质量恒星的形成。

英文摘要:

Magnetic fields constitute an energetic component of the interstellar medium in galaxies and hence can affect the formation of galactic structures. Sensitive resolved radio continuum observations together with statistical studies in galaxy samples are performed to investigate the origin and the impact of the magnetic fields. The JVLA cloud-scale survey of the local group galaxy, M33, unveils strong tangled magnetic field along the spiral arms and in the galaxy center indicating amplification due to compression and local shear in molecular clouds. Studying a sample of non-cluster, non-interacting galaxies, we find that the large-scale ordered magnetic field scales with the rotation speed of galaxies. The total and disordered magnetic fields scales with the star formation rate in normal star forming galaxies. On the other hand, a strong magnetic field in the center of NGC 1097 -- a massive galaxy undergoing quenching -- is found responsible for decelerating its massive star formation. Putting these results together, it is deduced that 1) the Universe was highly magnetized short after the peak of the massive star birth at about 1 Gyr after the Big Bang and 2) the strong magnetic field has possibly acted as back reaction after this time, quenching the massive star formation and stimulating the creation of low-mass stars in massive galaxies.

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