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arXiv 1901.01434astro-ph.COastro-ph.HE
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宇宙学磁制动与高红移超大质量黑洞的形成

Cosmological magnetic braking and the formation of high-redshift, super-massive black holes

Kanhaiya L. Pandey, Shiv K. Sethi, Bharat Ratra

摘要:

本文研究了在高红移下大质量($\gtrsim 10^{4} M_\odot$)直接坍缩黑洞(DCBH)形成过程中由于原始磁场引起的磁制动效应。在轴对称的假设下,解析计算了磁制动对坍缩到由引力潮汐力矩旋转而成的大质量暗物质晕($\simeq 10^{7-9} M_\odot$)势阱中的气体角动量的影响.我们发现,一个强度为$B_0\simeq 0.1$ ~nG(共动)的原始磁场可以消除由潮汐力矩引起的下落气体的初始角动量,从而显著降低了DCBH形成的角动量势垒。这些磁场强度与天体物理学和宇宙学测量的原始磁场的边界一致,它们足够大,可以为观测到的银河系磁场提供种子。

英文摘要:

We study the effect of magnetic braking due to a primordial magnetic field in the context of the formation of massive ($\gtrsim 10^{4} M_\odot$) direct collapse black holes (DCBHs) at high redshifts. Under the assumption of axial symmetry, we analytically compute the effect of magnetic braking on the angular momentum of gas collapsing into the potential well of massive dark matter haloes ($\simeq 10^{7-9} M_\odot$) which are spun up by gravitational tidal torques. We find that a primordial magnetic field of strength $B_0\simeq 0.1$~nG (comoving) can remove the initial angular momentum gained by the in-falling gas due to tidal torques, thus significantly lowering the angular momentum barrier to the formation of DCBHs. These magnetic field strengths are consistent with the bounds on primordial fields from astrophysical and cosmological measurements and they are large enough to seed observed galactic magnetic fields.

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