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What: |
The Hot and Cold Spots in Five-year WMAP Data |
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( PMO)) |
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Who: |
Dr.Hou,Zh |
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When: |
Wednesday afternoon ,Oct.22th,2:00 p.m. |
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Where: |
Room 327, Office Block, 2 West Beijing Road (PMO, CAS) |
abstract
We present an intensive frequentist analysis on the one-point statistics (number, mean, variance, skewness and kurtosis) and two-point correlation functions of the local extrema of the cosmic microwave background in five-year Wilkinson Microwave Anisotropy Probe ( WMAP ) data. Hypothesis test on one-point statistics indicates a extreme low-variance of hot and cold spots that the observation at all the bands of WMAP is rejected at 95% C.L.outside KQ75 mask and additional two northern hemispheres, based on our Gaussian simulations. Dipole modulation and Galactic equatorial cut are performed to fit the North-South power asymmetry and eliminate probable residual Galactic foreground contamination but still proved inadequate to fit the statistics.It is improved until we remove first 5 moments,and much better for l rmv =10.Two- point correlation functions of local extrema are calculated for both temperature pair product (T-T) and spatial pair-counting (P-P). The WMAP observed ones show weak correlation on scales below 20 deg and even 3σ confidence lower for T-T once thresholds applied on extrema on the full-and northern sky.The P-P correlation structure corresponds to the scale properties of the temperature“clustering” regions of large-scale moments.It is the smaller and less fluctuated hot and cold “clusters” of l =2~5 as a strong evidence that suppress the angular correlation of local extrema, and is even the origin of low-variance of extrema on northern sky.
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