Measurement of the Cosmic Microwave Background Bispectrum on the COBE DMR Sky Maps
Measurement of the Cosmic Microwave Background Bispectrum on the COBE DMR Sky Maps
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COBE DMR 天空图上宇宙微波背景双谱的测量
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
K. Górski
中科院分区：
文献类型：
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作者：
E. Komatsu;B. Wandelt;D. Spergel;A. Banday;K. Górski
从COBE差分微波辐射计(DMR)4年天图上测量了宇宙微波背景(CMB)辐射各向异性的角双谱。角双谱是三点相关函数的调和变换，类似于角功率谱，是两点相关函数的调和变换。首先，研究了双谱和归一化双谱的统计性质。我们发现后者更适用于统计分析；归一化双谱的分布是非常高斯的，而裸双谱分布是高度非高斯的。然后，我们测量了归一化双谱的466个模，所有三点组态的独立组合直到最大多极子20，该模对应于DMR光束尺寸。通过测量10倍于前人工作总和的模式，我们测试了DMR图的高斯性。我们将数据与模拟的高斯实现进行比较，发现在逐个模式的基础上没有显著检测到归一化双谱。我们还发现，先前报道的归一化双谱的检测与统计涨落是一致的。通过对慢滚膨胀激发的原始CMB双谱数据的理论预测，我们对表征膨胀中的非线性的参数施加了弱约束。同时拟合从星际尘埃和同步加速器模板图估计的前景双谱，表明尘埃和同步辐射对银河系高纬度的双谱都没有显著贡献。我们得出结论，DMR图与高斯分布是一致的。
We measure the angular bispectrum of the cosmic microwave background (CMB) radiation anisotropy from the COBE Differential Microwave Radiometer (DMR) 4 yr sky maps. The angular bispectrum is the harmonic transform of the three-point correlation function, analogous to the angular power spectrum, the harmonic transform of the two-point correlation function. First, we study statistical properties of the bispectrum and the normalized bispectrum. We find the latter more useful for statistical analysis; the distribution of the normalized bispectrum is very much Gaussian, while the bare bispectrum distribution is highly non-Gaussian. Then, we measure 466 modes of the normalized bispectrum, all independent combinations of three-point configurations up to a maximum multipole of 20, the mode corresponding to the DMR beam size. By measuring 10 times as many modes as the sum of previous work, we test the Gaussianity of the DMR maps. We compare the data with the simulated Gaussian realizations, finding no significant detection of the normalized bispectrum on a mode-by-mode basis. We also find that the previously reported detection of the normalized bispectrum is consistent with a statistical fluctuation. By fitting a theoretical prediction to the data for the primordial CMB bispectrum, which is motivated by slow-roll inflation, we put a weak constraint on the parameter characterizing nonlinearity in inflation. Simultaneously fitting the foreground bispectra estimated from interstellar dust and synchrotron template maps shows that neither dust nor synchrotron emission significantly contributes to the bispectrum at high Galactic latitude. We conclude that the DMR map is consistent with Gaussianity.