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arXiv 1503.04827astro-ph.CO
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原始磁场对电离历史的影响

Effect of primordial magnetic fields on the ionization history

Jens Chluba, Daniela Paoletti, Fabio Finelli, Jose-Alberto Rubino-Martin

摘要:

原始磁场(PMF)在比光子扩散和自由流尺度更小的尺度上衰减。这导致普通物质(电子和重子)的加热,这影响了我们宇宙的热和电离历史。在这里,我们研究加热的效果,由于双极扩散和衰减的磁湍流。我们发现,与CosmoRec相比,用recfast计算的电离历史的变化被显著高估。造成这种差异的主要物理原因是光电离系数必须用辐射温度而不是物质温度来计算。在改变这一方面后,发现与CosmoRec的一致性很好。使用普朗克2013年的数据,只考虑PMF诱导加热的影响,我们发现了一个上限的r.m.s.磁场振幅B0 < 1.1 nG(95% c.l.)的随机背景的PMF与近尺度不变的功率谱。我们还讨论了不确定性的近似加热速率和差异,就以前的研究。我们的研究结果是重要的推导的约束条件的PMF功率谱测量的宇宙微波背景各向异性与全任务普朗克数据。他们也可能改变一些计算的PMF诱导的原始化学和21厘米信号的影响。

英文摘要:

Primordial magnetic fields (PMF) damp at scales smaller than the photon diffusion and free-streaming scale. This leads to heating of ordinary matter (electrons and baryons), which affects both the thermal and ionization history of our Universe. Here, we study the effect of heating due to ambipolar diffusion and decaying magnetic turbulence. We find that changes to the ionization history computed with recfast are significantly overestimated when compared with CosmoRec. The main physical reason for the difference is that the photoionization coefficient has to be evaluated using the radiation temperature rather than the matter temperature. A good agreement with CosmoRec is found after changing this aspect. Using Planck 2013 data and considering only the effect of PMF-induced heating, we find an upper limit on the r.m.s. magnetic field amplitude of B0 < 1.1 nG (95% c.l.) for a stochastic background of PMF with a nearly scale-invariant power spectrum. We also discuss uncertainties related to the approximations for the heating rates and differences with respect to previous studies. Our results are important for the derivation of constraints on the PMF power spectrum obtained from measurements of the cosmic microwave background anisotropies with full-mission Planck data. They may also change some of the calculations of PMF-induced effects on the primordial chemistry and 21cm signals.

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