Predictions of Cosmic Microwave Background Foreground Dust Polarization Using Velocity Gradients
Predictions of Cosmic Microwave Background Foreground Dust Polarization Using Velocity Gradients
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DOI：
10.3847/1538-4357/ab60a5
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发表时间：
2019-10
期刊：
影响因子：
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通讯作者：
Yue Hu;K. Yuen;A. Lazarian
中科院分区：
文献类型：
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作者：
Yue Hu;K. Yuen;A. Lazarian
对宇宙微波背景波动的观测提供了有关宇宙原始不均匀性的信息。然而，暴胀引力波的 B 模式偏振受到由星际磁场排列的尘埃产生的银河系前景偏振辐射的污染。为了追踪磁场，我们使用速度梯度技术 (VGT)，该技术采用了对磁流体动力学湍流运动本质的现代理解。在本文中，我们将VGT与主成分分析（PCA）相结合来提高磁场追踪的准确性。我们将 VGT-PCA 应用于 GALFA-H i 调查的高分辨率中性氢数据来预测尘埃的偏振。我们报告称，预测的尘埃偏振方向与普朗克 353 GHz 报告的方向具有良好的对应性，两者之间的对准测量值≃0.79 ± 0.01。我们表明，我们的结果在统计上与磁场追踪方面的普朗克极化一致。我们发现整个天空的粉尘排放效率变化很小。使用我们预测的偏振图，我们计算了 E 模式和 B 模式的比率，并表明 BB/EE ≃ 0.53 ± 0.10，这与普朗克偏振的结果相似。
Observations of fluctuations in the cosmic microwave background provide information about primordial inhomogeneities in the universe. However, the B-mode polarization of the inflationary gravitational wave is contaminated by the Galactic foreground polarized radiation arising from dust aligned by interstellar magnetic fields. To trace magnetic fields, we use the Velocity Gradient Technique (VGT), which employs modern understanding of the nature of magnetohydrodynamic turbulent motions. In this paper, we combine the VGT with Principal Component Analysis (PCA) to improve the accuracy of magnetic field tracing. We apply the VGT–PCA to the high-resolution neutral hydrogen data from the GALFA-H i survey to predict the polarization of dust. We report that the predicted directions of dust polarization provide good correspondence with those reported by Planck 353 GHz, with the alignment measure between the two ≃0.79 ± 0.01. We show that our results statistically agree with the Planck polarization in terms of magnetic field tracing. We find that the variation of dust emission efficiency across the sky is small. Using our maps of predicted polarization, we calculate the ratio of the E- and B-modes, and show that BB/EE ≃ 0.53 ± 0.10, which is similar to the result from Planck polarization.