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arXiv 0705.2861astro-ph
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星系团和星系法拉第旋转的二次B模偏振

Secondary B-mode polarization from Faraday rotation in clusters and galaxies

Hiroyuki Tashiro, Nabila Aghanim, Mathieu Langer

备注：
Accepted for publication in MNRAS
发表信息：
Mon.Not.Roy.Astron.Soc.384:733-746,2008
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摘要：

我们重新讨论了当宇宙微波背景光子穿过磁化等离子体时法拉第旋转引起的极化。我们计算了质量从$10^{11}$到$10^{16.5} M_\odot$的星系和星系团中由于磁场引起的法拉第旋转的次级B模角功率谱。我们调查其依赖于电子和磁场的配置文件。也就是说，我们考虑的电子密度的β分布，以及电子密度分布的基础上的Navarro-Frenk-White暗物质的档案。我们模拟的磁场结构的星系和集群的动机最近的观测。我们进一步考虑其红移的演变，我们研究其相干长度的重要性。我们发现法拉第旋转产生的B模偏振依赖于归一化参数$C_l\propto σ_8^{5-6}$。在30 GHz的$σ_8=0.8$，法拉第旋转的B模式范围之间的$0.01 {μ\rm K}^2$和$4 \times 10^{-3} {μ\rm K}^2$在$l=10^4$的情况下，最大相干场。对于较小的相干长度，这些振幅较小，并且它们在较高的多极子处达到峰值。

英文摘要：

We revisit the polarisation induced by Faraday rotation when Cosmic Microwave Background photons traverse magnetised plasma. We compute the secondary B-mode angular power spectrum from Faraday rotation due to magnetic fields in galaxies and galaxy clusters with masses ranging from $10^{11}$ to $10^{16.5} M_\odot$. We investigate its dependence on the electron and the magnetic field profiles. Namely, we consider both the beta-profile of electron density as well as an electron density distribution based on the Navarro-Frenk-White dark matter profile. We model the magnetic field structure in galaxies and clusters motivated by recent observations. We further account for its redshift evolution and we examine the importance of its coherence length. We find that the B-mode polarisation from Faraday rotation depends on the normalisation parameter $C_l\propto σ_8^{5-6}$. At 30 GHz for $σ_8=0.8$, the B-modes from Faraday rotation range between $0.01 {μ\rm K}^2$ and $4 \times 10^{-3} {μ\rm K}^2$ at $l=10^4$ in the case of a maximally coherent fields. For smaller coherence lengths, those amplitudes are smaller and they peak at higher multipoles.

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