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arXiv 0704.3736astro-ph
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WMAP数据中的对齐和符号强度异常

Alignment and signed-intensity anomalies in WMAP data

P. Vielva, Y. Wiaux, E. Martinez-Gonzalez, P. Vandergheynst

摘要:

利用WMAP三年数据,通过对信号进行球面方向可调小波分解,发现了宇宙微波背景(CMB)局部特征的显著排列和符号强度异常。首先,对准分析确定了天空中的两个平均优选平面,两者的法向轴都接近CMB偶极轴。第一平面由局部CMB特征被错误地对准的方向限定。在这个平面上还确定了一个平均优选轴,它非常靠近黄道两极轴。第二个平面由局部CMB特征避免的方向定义。这种排列异常为最近的结果提供了进一步的见解(Wiaux等人,2006年)。其次,符号强度分析确定了南银河半球三个平均的首选方向,其局部CMB特征的温度过高或过低:一个冷点基本上与已知的冷点相同(Vielva et al. 2004),第二个冷点非常接近CMB偶极轴的南端,以及一个热点靠近黄道极轴的南端。在这两种分析中,观测到的异常在小波尺度上对应于天球上10度左右的角度大小,全球显著性水平约为1%。进一步的研究表明,对齐和符号强度异常只有非常部分相关。仪器噪声,前景排放,以及其他系统的某种形式,强烈拒绝作为可能的起源的检测。一个解释可能仍然设想在一个全球违反宇宙的各向同性,诱导固有的统计各向异性的CMB。

英文摘要:

Significant alignment and signed-intensity anomalies of local features of the cosmic microwave background (CMB) are detected on the three-year WMAP data, through a decomposition of the signal with steerable wavelets on the sphere. Firstly, an alignment analysis identifies two mean preferred planes in the sky, both with normal axes close to the CMB dipole axis. The first plane is defined by the directions toward which local CMB features are anomalously aligned. A mean preferred axis is also identified in this plane, located very close to the ecliptic poles axis. The second plane is defined by the directions anomalously avoided by local CMB features. This alignment anomaly provides further insight on recent results (Wiaux et al. 2006). Secondly, a signed-intensity analysis identifies three mean preferred directions in the southern galactic hemisphere with anomalously high or low temperature of local CMB features: a cold spot essentially identified with a known cold spot (Vielva et al. 2004), a second cold spot lying very close to the southern end of the CMB dipole axis, and a hot spot lying close to the southern end of the ecliptic poles axis. In both analyses, the anomalies are observed at wavelet scales corresponding to angular sizes around 10 degress on the celestial sphere, with global significance levels around 1%. Further investigation reveals that the alignment and signed-intensity anomalies are only very partially related. Instrumental noise, foreground emissions, as well as some form of other systematics, are strongly rejected as possible origins of the detections. An explanation might still be envisaged in terms of a global violation of the isotropy of the Universe, inducing an intrinsic statistical anisotropy of the CMB.

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