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Systematical Effects on the Wilkinson Microwave Anisotropy

 Probe Suggest Necessary Corrections and Even New Physics

 

The Wilkinson microwave anisotropy probe (WMAP) is a spacecraft used to detect the cosmic microwave background (CMB) anisotropy, whose results are regarded as the foundation of precision cosmology. However, Ti-Pei Li and Hao Liu of Tsinghua University and Institute of High Energy Physics of Chinese Academy of Sciences have discovered several systematical effects that cast strong doubts on the WMAP results, and suggest necessary corrections or even new physics.

For example, the spacecraft detects the CMB anisotropy by two antennas separated by 141 degrees; 141 is apparently an artificial number, which should not be ��seen�� on the natural all-sky CMB maps. However, it has definitely been seen: the hot regions on the CMB maps, like the Galactic plane and the planets, are confirmed to have suppressed the temperatures of the pixels that are right 141 degrees apart from them (Fig. 1), and such ��temperature suppression�� has been detected by several methods (Liu & Li, 2009). It has also been confirmed that such correlation can significantly contaminate the large-scale two-point correlation function (Aurich et al., 2010).

 


Fig. 1: The correlation coefficients between the temperature of the center hot region and the average temperature on rings of different separation angles. Strongest negative correlation is seen right around 141 degrees, illustrating the existence of ring contamination on the CMB maps.

 

More importantly, Li and Liu have discovered that the CMB quadrupole component has also been seriously contaminated by systematical effects, such as the sidelobe uncertainty. They have described how such systematical effects, independent of the CMB signal, can create an artificial CMB quadrupole through the WMAP observation and data reduction procedure (Liu & Li 2011a, 2011b), and they have provided convincing evidence against WMAP by confirming that such systematic distortion is almost the same to the claimed real ��CMB quadrupole�� (Fig. 2). Therefore, the WMAP CMB quadrupole is highly suspect, and we must consider the possibility that the real CMB quadrupole is almost zero; it is a possibility which could lead to new physics.

 


Fig. 2: Left panel: The estimated temperature distortion, derived without using any CMB data. Right panel: The released WMAP CMB quadrupole component derived from WMAP5 V and W bands, both in Galactic coordinates and in units of mK. The similarity between these figures casts large doubts on the WMAP result.

 

Liu Hao, Li Ti-Pei. (2009). Systematic distortion in cosmic microwave background maps, Science in China G: Physics and Astronomy, 52, 804-808

Liu Hao, Li Ti-Pei. (2011a). Pseudo-Dipole Signal Removal from WMAP Data, Chinese Science Bulletin, 56(1) 29-33

Liu Hao, Li Ti-Pei. (2011b). Observational Scan-Induced Artificial Cosmic Microwave Background Anisotropy , Astrophys. J., 732, 125-130

Aurich R., Lustig S., Steiner F. (2010). Hot pixel contamination in the CMB correlation function? Classical and Quantum Gravity, 27, 095009.

 

 
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