通过宽带无线电分光偏振测量的CMB前景测量：SKA-MPG望远镜的前景
CMB foreground measurements through broad-band radio spectro-polarimetry: prospects of the SKA-MPG telescope
摘要：
精确测量前景同步辐射污染了微弱的偏振宇宙微波背景辐射，是下一代宇宙微波背景实验的主要挑战。为了解决这个问题，正在2至40 GHz之间的无线电频率进行专门的前景测量实验。前景偏振同步辐射测量是特别具有挑战性的，主要是由于在法拉第旋转的存在下的复杂的频率依赖性，并且最好通过在频率$\lesssim 5$ GHz的宽分数带宽偏振测量来恢复。工作在1.7 ~ 3.5GHz（S波段）的15米SKA-MPG望远镜将为测量前景偏振同步辐射提供一个独特的机会。在这里，我们提出了一个南方天空调查的范围在S波段在1度角分辨率，并探讨其应用强大的技术，如斯托克斯$Q$，$U$拟合和RM合成的额外优势。用这台望远镜进行的南天偏振巡天，与其他正在进行的稍高频率的工作相结合，将为建模和外推前景偏振同步辐射到CMB频率（$\gtrsim80$ ~GHz）提供极好的频率覆盖范围，均方根亮温优于10 nK/1度$^2$。我们发现，这项调查将是至关重要的了解法拉第去极化的影响，特别是在低银河系纬度地区。这将允许更好的前景清理，从而将大大有助于进一步改进成分分离分析，并增加可用于\textit{Planck}数据宇宙学分析的天空面积，以及未来的\textit{LiteBIRD}任务。
英文摘要：
Precise measurement of the foreground synchrotron emission, which contaminates the faint polarized cosmic microwave background radiation (CMB), is a major challenge for the next-generation of CMB experiments. To address this, dedicated foreground measurement experiments are being undertaken at radio frequencies between 2 and 40 GHz. Foreground polarized synchrotron emission measurements are particularly challenging, primarily due to the complicated frequency dependence in the presence of Faraday rotation, and are best recovered through broad fractional-bandwidth polarization measurements at frequencies $\lesssim 5$ GHz. A unique opportunity for measuring the foreground polarized synchrotron emission will be provided by the 15-m SKA-MPG telescope operating in the frequency range 1.7 to 3.5~GHz (S-Band). Here, we present the scope of a Southern sky survey in S-Band at 1 degree angular resolution and explore its added advantage for application of powerful techniques, such as, Stokes $Q$, $U$ fitting and RM-synthesis. A full Southern-sky polarization survey with this telescope, when combined with other on-going efforts at slightly higher frequencies, will provide an excellent frequency coverage for modeling and extrapolating the foreground polarized synchrotron emission to CMB frequencies ($\gtrsim80$~GHz) with rms brightness temperature better than 10~nK per 1 degree$^2$. We find that this survey will be crucial for understanding the effects of Faraday depolarization, especially in low Galactic latitude regions. This will allow better foreground cleaning and thus will contribute significantly in further improving component separation analyses and increase usable sky area for cosmological analysis of the \textit{Planck} data, and the \textit{LiteBIRD} mission in the future.
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