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arXiv 2301.10045astro-ph.CO
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通过原初黑洞盘产生原初磁场

Primordial magnetic field generation via primordial black hole disks

Theodoros Papanikolaou, Konstantinos N. Gourgouliatos

备注：
1)To appear in Physical Review D. 2)Major revisions regarding the derivation of the magnetic field power spectrum
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AI总结：

本研究提出一种通过超大质量原初黑洞盘的Biermann电池效应产生大尺度原初磁场的新机制，推导了种子磁场的表达式，并给出了对应现今观测所需原初黑洞质量的下限范围。

摘要：

贯穿星系际介质的大尺度原初磁场（PMFs）在宇宙中被普遍观测到，对宇宙演化起着关键作用。它们的起源仍存在争议，是一个非常活跃的研究领域。在本文中，我们提出了一种新颖的、自然的从头计算机制，通过在大爆炸核合成与复合时期之间形成的超大质量原初黑洞（PBHs）的途径来解释这类原初磁场的起源。具体而言，通过考虑配备局部等温盘的原初黑洞，我们研究了由原初等离子体围绕黑洞的涡旋状运动引发的Biermann电池（比尔曼电池）效应所产生的种子磁场（MF）。最后，通过考虑单色原初黑洞质量分布并推导相关的磁场功率谱，我们对星系际尺度上、红移$z=30$（通常认为星系在此时形成）时的种子原初磁场进行了保守估计，其表达式为$B\backsimeq 10^{-30}\mathrm{G}\left(\frac{\ell_\mathrm{R}}{10^6}\right)^2\left(\frac{M_\mathrm{PBH}}{10^{14}M_\odot}\right)^{5/2}$，其中$M_\mathrm{PBH}$是原初黑洞质量，$\ell_\mathrm{R}\equiv R_\mathrm{d}/R_\mathrm{ISCO}$是盘半径$R_\mathrm{d}$与最内稳定圆轨道半径$R_\mathrm{ISCO}$的比值。十分有趣的是，通过要求种子原初磁场达到$10^{-30}\mathrm{G}$量级（这是产生现今星系际尺度上$10^{-18}\mathrm{G}$磁场所必需的），我们发现原初黑洞质量的下限处于$[10^{10}- 10^{16}]M_\odot$范围内，具体数值取决于原初黑洞盘的半径。

英文摘要：

Large scale primordial magnetic fields (PMFs) threading the intergalactic medium are observed ubiquitously in the Universe playing a key role in the cosmic evolution. Their origin is still debated constituting a very active field of research. In the present article, we propose a novel natural ab initio mechanism for the origin of such PMFs through the portal of supermassive primordial black holes (PBHs) forming between the Big Bang Nucleosynthesis and the recombination era. In particular, by considering PBHs furnished with a locally isothermal disk we study the generation of a Biermann battery induced seed magnetic field (MF) due to the vortexlike motion of the primordial plasma around the black hole. Finally, by considering monochromatic PBH mass distributions and deriving the relevant MF power spectrum we make a conservative estimate for the seed PMF in intergalactic scales and at redshift $z=30$, when typical galaxies are considered to form, which reads as $B\simeq 10^{-30}\mathrm{G}\left(\frac{\ell_\mathrm{R}}{10^6}\right)^2\left(\frac{M_\mathrm{PBH}}{10^{14}M_\odot}\right)^{5/2}$, where $M_\mathrm{PBH}$ is the PBH mass and $\ell_\mathrm{R}\equiv R_\mathrm{d}/R_\mathrm{ISCO}$, is the ratio of the radius of the disk, $R_\mathrm{d}$ over the radius of the innermost stable circular orbit, $R_\mathrm{ISCO}$. Interestingly enough, by requiring to seed a PMF of the order of $10^{-30}\mathrm{G}$ necessary to give rise to a present day $10^{-18}\mathrm{G}$ in intergalactic scales, we find a lower bound on the PBH mass within the range $[10^{10}- 10^{16}]M_\odot$ depending on the radius of the PBH disk.

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