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Xin Liu and Shuang Nan Zhang 2005, ApJ, in press, v630 (astro-ph/0504589) Tsinghua University

Non-Gaussianity Due to Possible Residual Foreground Signals in Wilkinson Microwave Anistropy Probe First-Year Data Using Spherical Wavelet Approaches. Xin Liu and Shuang Nan Zhang 2005, ApJ, in press, v630 (astro-ph/0504589) Tsinghua University. Outline. Introduction

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Xin Liu and Shuang Nan Zhang 2005, ApJ, in press, v630 (astro-ph/0504589) Tsinghua University

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  1. Non-Gaussianity Due to Possible Residual Foreground Signals in Wilkinson Microwave Anistropy Probe First-Year Data Using Spherical Wavelet Approaches Xin Liu and Shuang Nan Zhang 2005, ApJ, in press, v630 (astro-ph/0504589) Tsinghua University

  2. Outline • Introduction 2. Wavelets on the sphere 3. Non-Gaussianity analysis 4. Results 5. Conclusions and discussions

  3. 1. Introduction • The importance of the test of non-Gaussianity of CMB temperature anisotropies • Current status of the test • Causes of the CMB non-Gaussianity • Foreground removal and the foreground template • Spherical wavelet approaches

  4. 2. Wavelets on the sphere • The general theory • Spherical wavelet: the spherical counterpart of the planar wavelet • Practical implementation • Yet Another Wavelet toolbox (http://www.fyma.ucl.ac.be/projects/yawtb) • Spherical wavelet basis • Spherical Mexican Hat Wavelet and Spherical Morlet Wavelet

  5. 3. Non-Gaussianity analysis • Non-Gaussianity statistics • Monte Carlo simulations

  6. 4. Results • Spherical wavelet coefficient statistics

  7. Non-Gaussianity localization

  8. Sources of non-Gaussianity

  9. Sources of non-Gaussianity Fig. 10a in Bennett et al. 2003

  10. Sources of non-Gaussianity

  11. 5. Conclusions and Discussions • In the wavelet space, deviations from Gaussianity are found in skewness at scales from 11 to 14 degrees on the sky and in kurtosis on scales smaller than 11 degrees. • Several possible non-Gaussian spots are detected in the real space. • On the possible sources of the detected non-Gaussianity: • Systematic effects have been excluded; • Foreground templates adopted by the WMAP team also make no significant contribution; • The most likely source of the detected non-Gaussianity is the residual foreground signals in the map. • It is still premature to test more precisely on the non-Gaussianity of the intrinsic CMB fluctuations before we can identify the origin of these foreground signals, understand its nature, and finally remove them from the CMB maps completely.

  12. WMAP and EGRET cross-correlation in wavelet space: a foreground residual detection

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