The significance of anisotropic signals hiding in the Type Ia supernovae
The significance of anisotropic signals hiding in the Type Ia supernovae
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Ia型超新星中隐藏的各向异性信号的意义
DOI：
10.1093/mnras/stw995
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发表时间：
2016-04
影响因子：
4.8
通讯作者：
Zhe Chang
中科院分区：
文献类型：
--
作者：
Hai-Nan Lin;Xin Li;Zhe Chang
我们使用了两种不同的方法，即偶极子拟合（DF）和半球比较（HC），来搜索隐藏在Union2.1数据集中的各向异性信号。我们发现，用这两种方法得到的最大物质密度方向彼此相差约114A度。我们构建了四个类似union2.1的模拟样本来检验这两种方法的统计显著性。结果表明，DF方法具有显著的统计意义，而HC方法受天空中数据点分布的影响有很强的偏倚。然后我们假设距离模量的各向异性主要是由物质密度的各向异性引起的，并将其建模为偶极子形式Omega(M) = Omega(M0)（1 - cos θ）。我们将我们的模型拟合到Union2.1，发现最大物质密度的方向与用DF方法得到的方向很好地一致，但与之前声称的方向有很大的不同。蒙特卡罗模拟表明，我们的方法在统计上比HC方法更显著，尽管不如DF方法显著。如果数据点在天空中均匀分布，则可以进一步提高统计显著性。然而，由于目前超新星数据的质量较低，现在断言宇宙有任何优先方向还为时过早。
We use two different methods, i.e. dipole-fitting (DF) and hemisphere comparison (HC), to search for the anisotropic signals hiding in the Union2.1 data set. We find that the directions of maximum matter density derived using these two methods are about 114A degrees away from each other. We construct four Union2.1-like mock samples to test the statistical significance of these two methods. It is shown that DF method is statistically significant, while HC method is strongly biased by the distribution of data points in the sky. Then we assume that the anisotropy of distance modulus is mainly induced by the anisotropy of matter density, which is modelled to be the dipole form Omega(M) = Omega(M0)(1 - cos theta). We fit our model to Union2.1, and find that the direction of maximum matter density is well consistent with the direction derived using DF method, but it is very different from the direction previously claimed. Monte Carlo simulations show that our method is statistically more significant than HC method, although it is not as significant as DF method. The statistical significance can be further improved if the data points are homogeneously distributed in the sky. Due to the low quality of present supernovae data, however, it is still premature to claim that the Universe has any preferred direction.
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DOI：
10.1103/physrevd.87.123522
发表时间：
2013-03
期刊：
Physical Review D - Particles, Fields, Gravitation and Cosmology
影响因子：
--
作者：
Cai, Rong-Gen;Ma, Yin-Zhe;Tang, Bo;Tuo, Zhong-Liang
通讯作者：
Tuo, Zhong-Liang
用Union2.1数据寻找首选方向
影响因子：
4.8
作者：
Yang, Xiaofeng;Wang, F. Y.;Chu, Zhe
通讯作者：
Chu, Zhe
DOI：
10.1086/154576
发表时间：
1976-08
期刊：
The Astrophysical Journal
影响因子：
--
作者：
E. Turner
通讯作者：
E. Turner
影响因子：
5
作者：
A. Mariano;L. Perivolaropoulos
通讯作者：
A. Mariano;L. Perivolaropoulos
不同 Ia 型超新星群对宇宙的各向异性的约束
影响因子：
4.4
作者：
Chang Zhe;Li Xin;Lin Hai-Nan;Wang Sai
通讯作者：
Wang Sai