arXiv 2101.092812021-01-22astro-ph.CO

原始磁场存在下的第一个恒星形成

First Star Formation in the Presence of Primordial Magnetic Fields

Daegene Koh, Tom Abel, Karsten Jedamzik

备注：: 8 pages, 6 figures, submitted to ApJL
DOI：: 10.3847/2041-8213/abe8dd

摘要：

最近有人声称，原始磁场可以缓解宇宙学上的哈勃张力。我们认为，这种领域的第一个宇宙学对象的形成的影响，形成小晕的恒星，为当今的磁场强度范围内的$2\times 10^{-12}$ - $2\times 10^{-10}$ G。这些值对应于阿尔文速度与$v_a/c_s\approx 0.03 - 3$声速的初始比值。我们发现，当$v_a/c_s\ll 1$，效果是温和的。而当发生$v_a\sim c_s$时，引力坍缩的开始时间延迟，持续时间延长了$Δ$ z = 2.5的红移.当$v_a > c_s$时，坍缩被完全抑制，并且迷你晕继续增长，并且在达到原子冷却极限之前不太可能坍缩。利用目前对原始磁场的观测极限，我们得出结论，暴胀产生的原始磁场可能对第一颗恒星的形成产生重大影响，而后暴胀产生的磁场则不会。

英文摘要：

It has been recently claimed that primordial magnetic fields could relieve the cosmological Hubble tension. We consider the impact of such fields on the formation of the first cosmological objects, mini-halos forming stars, for present-day field strengths in the range of $2\times 10^{-12}$ - $2\times 10^{-10}$ G. These values correspond to initial ratios of Alvén velocity to the speed of sound of $v_a/c_s\approx 0.03 - 3$. We find that when $v_a/c_s\ll 1$, the effects are modest. However, when $v_a\sim c_s$, the starting time of the gravitational collapse is delayed and the duration extended as much as by $Δ$z = 2.5 in redshift. When $v_a > c_s$, the collapse is completely suppressed and the mini-halos continue to grow and are unlikely to collapse until reaching the atomic cooling limit. Employing current observational limits on primordial magnetic fields we conclude that inflationary produced primordial magnetic fields could have a significant impact on first star formation, whereas post-inflationary produced fields do not.

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