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arXiv 1802.01145astro-ph.GAastro-ph.COastro-ph.IM
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S-PASS认为2.3 GHz极化银河同步加速器对CMB观测是一种污染

The S-PASS view of polarized Galactic Synchrotron at 2.3 GHz as a contaminant to CMB observations

N. Krachmalnicoff, E. Carretti, C. Baccigalupi, G. Bernardi, S. Brown, B. M. Gaensler, M. Haverkorn, M. Kesteven, F. Perrotta, S. Poppi, L. Staveley-Smith

备注：
accepted for publication on A&A
发表信息：
A&A 618, A166 (2018)
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摘要：

我们分析了南天发射线偏振在2.3 GHz的S波段偏振全天巡天S-PASS观测。我们的目的是研究扩散银河偏振同步加速器作为CMB B模观测的污染物的性质。本文利用角功率谱研究了S-PASS信号在银河系中高纬度的角分布。功率谱显示了作为\ell <200的多极函数的谱振幅的衰减，这是典型的漫发射。光谱可以近似为幂律C_{\ell} \propto \ell^{alpha}，α约为-3，其特征在于B/E比约为0.5。通过计算低频WMAP和Planck映射的功率谱，研究了偏振态下的同步辐射自聚焦效应。结果表明，在2.3-33 GHz的频率范围内，SED符合幂律，β_s=-3.22 \pm 0.08。将S-PASS偏振图与来自WMAP和Planck的偏振图相结合，我们导出了约30%天空上角分辨率为2°的同步加速器光谱指数图。恢复的分布峰值在约-3.2处。我们还测量同步辐射和热尘埃信号之间的显着空间相关性，跟踪普朗克353 GHz的通道。这种相关性在较大的角尺度上达到约40%，在度尺度上显著衰减。最后，我们使用的S-PASS地图来评估偏振同步辐射污染的CMB观测的B模式。此外，通过将S-PASS数据与普朗克353 GHz观测数据相结合，我们恢复了总偏振前景污染对B模的最小程度的映射，发现在任何频率下，天空中没有任何区域的污染低于等效高音标量比~10^-3。这一结果证实了在CMB B模式测量中观察高频和低频前景的重要性。

英文摘要：

We analyze the Southern Sky emission in linear polarization at 2.3 GHz as observed by the S-band Polarization All Sky Survey S-PASS. Our purpose is to study the properties of the diffuse Galactic polarized synchrotron as a contaminant to CMB B-mode observations. We study the angular distribution of the S-PASS signal at intermediate and high Galactic latitudes by means of angular power spectra. Power spectra, show a decay of the spectral amplitude as a function of multipole for \ell<200, typical of the diffuse emission. Spectra can be approximated by a power law C_{\ell}\propto\ell^{alpha}, with alpha~-3, and characterized by a B-to-E ratio of ~0.5. We study the synchrotron SED in polarization by computing power spectra of the low frequency WMAP and Planck maps. Results show that the SED, in the frequency range 2.3-33 GHz, is compatible with a power law with beta_s=-3.22\pm0.08. Combining S-PASS polarization maps with those coming from WMAP and Planck we derived a map of the synchrotron spectral index at angular resolution of 2° on about 30% of the sky. The recovered distribution peaks at the value around -3.2. We also measure a significant spatial correlation between synchrotron and thermal dust signals, as traced by the Planck 353 GHz channel. This correlation reaches about 40% on the larger angular scales, decaying considerably at the degree scales. Finally, we use the S-PASS maps to assess the polarized synchrotron contamination to CMB observations of the B-modes. Moreover, by combining S-PASS data with Planck 353 GHz observations, we recover a map of the minimum level of total polarized foreground contamination to B-modes, finding that there is no region of the sky, at any frequency, where this contamination lies below equivalent tenor-to-scalar ratio ~10^-3. This result confirms the importance of observing both high and low frequency foregrounds in CMB B-mode measurements.

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