Two-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: A First Detection of Atmospheric Circular Polarization at Q band
Two-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: A First Detection of Atmospheric Circular Polarization at Q band
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DOI：
10.3847/1538-4357/ab64e2
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发表时间：
2020-02-01
影响因子：
4.9
通讯作者：
Xu, Zhilei
中科院分区：
文献类型：
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作者：
Petroff, Matthew A.;Eimer, Joseph R.;Xu, Zhilei
地球磁场引起大气中分子氧磁偶极跃迁的塞曼分裂，从而产生毫米波范围内的偏振发射。这种偏振发射主要是圆偏振的，表现为具有偶极子形状天空图案的前景，用于偏振敏感的地面宇宙微波背景实验，例如宇宙学大角尺度测量仪（CLASS），它能够测量大角尺度圆偏振。利用大气排放理论和辐射传输形式，我们对该信号的预期幅度和空间分布进行了建模，并评估了智利北部阿塔卡马沙漠 CLASS 观测站的模型。然后，利用 CLASS Q 波段望远镜在 323 至 43.7 GHz 的两年观测结果，我们提出了对该信号的检测，并将观测到的信号与模型预测的信号进行了比较。我们恢复了磁北与真北之间的角度为-55°06，这与CLASS观测站的-59°的预期一致。当比较偶极子天空模式与模拟和数据导出的天空图的拟合时，偶极子方向匹配在一定程度内，测量的幅度匹配在大约 20% 之内。
The Earth's magnetic field induces Zeeman splitting of the magnetic dipole transitions of molecular oxygen in the atmosphere, which produces polarized emission in the millimeter-wave regime. This polarized emission is primarily circularly polarized and manifests as a foreground with a dipole-shaped sky pattern for polarization-sensitive ground-based cosmic microwave background experiments, such as the Cosmology Large Angular Scale Surveyor (CLASS), which is capable of measuring large angular scale circular polarization. Using atmospheric emission theory and radiative transfer formalisms, we model the expected amplitude and spatial distribution of this signal and evaluate the model for the CLASS observing site in the Atacama Desert of northern Chile. Then, using two years of observations at 323 to 43.7 GHz from the CLASS Q-band telescope, we present a detection of this signal and compare the observed signal to that predicted by the model. We recover an angle between magnetic north and true north of -55 06, which is consistent with the expectation of -59 for the CLASS observing site. When comparing dipole sky patterns fit to both simulated and data-derived sky maps, the dipole directions match to within a degree, and the measured amplitudes match to within similar to 20%.