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arXiv 2010.08366astro-ph.CO
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宇宙射电偶极：估计量和频率依赖性

The Cosmic Radio Dipole: Estimators and Frequency Dependence

Thilo M. Siewert, Matthias Schmidt-Rubart, Dominik J. Schwarz

备注：
19 pages, 10 figures; version accepted by A&A
发表信息：
A&A 653, A9 (2021)
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摘要：

宇宙射电偶极是宇宙学的基本兴趣。最近的研究揭示了关于观测到的宇宙射电偶极子的性质的公开问题。我们使用模拟源计数地图来测试一个线性和二次估计其可能的偏见估计偶极振幅相对于掩蔽程序。我们发现的二次估计，然后用于分析TGSS-ADR 1，WENSS，SUMSS和NVSS的无线电源目录，传播超过十年的频率的优越性。同样的掩蔽策略应用于所有四个调查，以产生可比的结果。为了解决观测到的偶极子振幅的差异，我们交叉匹配位于分析频率范围两端的两个调查。对于线性估计，我们确定了一个一般的偏见估计偶极子方向。对于$10^7$模拟源的天空，二次估计器对CMB偶极子的位置偏移小于一度，估计偶极子振幅的绝对精度优于$10^{-3}$。对于四个射电源目录，我们发现一个增加的偶极子振幅随频率的降低，这是一致的结果，从文献和交叉匹配目录的结果。我们的结论是，对于所有分析的调查，所观察到的宇宙射电偶极子振幅超过预期，来自CMB偶极子，这不能解释的运动偶极子单独。

英文摘要：

The Cosmic Radio Dipole is of fundamental interest to cosmology. Recent studies revealed open questions about the nature of the observed Cosmic Radio Dipole. We use simulated source count maps to test a linear and a quadratic estimator for its possible biases in the estimated dipole amplitude with respect to the masking procedure. We find a superiority of the quadratic estimator, which is then used to analyse the TGSS-ADR1, WENSS, SUMSS, and NVSS radio source catalogues, spreading over a decade of frequencies. The same masking strategy is applied to all four surveys to produce comparable results. In order to address the differences in the observed dipole amplitudes, we cross-match the two surveys located at both ends of the analysed frequency range. For the linear estimator, we identify a general bias in the estimated dipole directions. The positional offsets of the quadratic estimator to the CMB dipole for skies with $10^7$ simulated sources is found to be below one degree and the absolute accuracy of the estimated dipole amplitudes is better than $10^{-3}$. For the four radio source catalogues, we find an increasing dipole amplitude with decreasing frequency, which is consistent with results from the literature and results of the cross-matched catalogue. We conclude that for all analysed surveys, the observed Cosmic Radio Dipole amplitudes exceed the expectation, derived from the CMB dipole, which can not be explained by a kinematic dipole alone.

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