论文标题
宇宙无线电偶极子：估计器和频率依赖性
The Cosmic Radio Dipole: Estimators and Frequency Dependence
论文作者
论文摘要
宇宙无线电偶极子是宇宙学的基本兴趣。最近的研究揭示了有关观察到的宇宙无线电偶极子的性质的开放问题。我们使用模拟的源计数图来测试与掩模过程相对于估计的偶极振幅中的线性和二次估计器的可能偏差。我们发现了二次估计量的优势，然后将其用于分析TGSS-ADR1，WENSS，SUMSS和NVSS无线电源目录，并扩散在十年的频率中。同样的掩蔽策略适用于所有四个调查，以产生可比的结果。为了解决观察到的偶极子振幅的差异，我们在分析频率范围的两端进行了两次调查。对于线性估计器，我们确定估计偶极子方向的一般偏差。发现二次估计器的位置偏移量为$ 10^7 $模拟来源的cmb偶极子的偶极子低于一个程度，并且估计偶极振幅的绝对准确性优于$ 10^{ - 3} $。对于四个无线电源目录，我们发现偶极幅度的增加随频率的降低，这与文献的结果和交叉匹配目录的结果一致。我们得出的结论是，对于所有分析的调查，观察到的宇宙无线电偶极子幅度超过了源自CMB偶极子的预期，这不能单独通过运动学偶极子来解释。
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.
