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arXiv 0812.3795astro-ph
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宇宙微波背景从全天空到次度尺度涨落的功率不对称性:宇宙是各向同性的吗?

Power Asymmetry in Cosmic Microwave Background Fluctuations from Full Sky to Sub-degree Scales: Is the Universe Isotropic?

F. K. Hansen, A. J. Banday, K. M. Gorski, H. K. Eriksen, P. B. Lilje

摘要:

我们重复并扩展了Eriksen等2004和Hansen等2004的分析,测试了宇宙微波背景(CMB)波动的各向同性。我们发现,半球功率不对称以前报道的最大规模l=2-40扩展到更小的规模。事实上,对于全多极范围l=2-600,在以θ =107 °为中心的半球中发现明显更大的功率,φ =226度)在银河系的同纬度和经度比在相反的半球与先前检测到的不对称的方向为l=2-40一致。我们采用模型选择试验,其中不对称的方向和幅度以及多极范围是自由参数。在0.4%的显著性水平下,考虑到描述它所需的附加参数,发现具有l=2-600的功率不对称分布的模型优于各向同性模型。在l=2-600之间的100个多极子的所有六个子范围中独立地发现了类似的不对称方向。600,我们的9800各向同性模拟地图没有一个显示出类似的一致方向的不对称性在这样一个大的多极范围。没有已知的系统性影响或前景被发现能够解释的不对称性。

英文摘要:

We repeat and extend the analysis of Eriksen et al 2004 and Hansen et al 2004 testing the isotropy of the Cosmic Microwave Background (CMB) fluctuations. We find that the hemispherical power asymmetry previously reported for the largest scales l=2-40 extend to much smaller scales. In fact, for the full multipole range l=2-600, significantly more power is found in the hemisphere centered at (theta=107 deg., phi=226 deg.) in galactic co-latitude and longitude than in the opposite hemisphere consistent with the previously detected direction of asymmetry for l=2-40. We adopt a model selection test where the direction and amplitude of asymmetry as well as the multipole range are free parameters. A model with an asymmetric distribution of power for l=2-600 is found to be preferred over the isotropic model at the 0.4% significance level taking into account the additional parameters required to describe it. A similar direction of asymmetry is found independently in all six subranges of 100 multipoles between l=2-600 and none of our 9800 isotropic simulated maps show a similarly consistent direction of asymmetry over such a large multipole range. No known systematic effects or foregrounds are found to be able to explain the asymmetry.

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