Asymmetries in the CMB anisotropy field
Abstract
We report on the results from two independent but complementary statistical analyses of the WMAP data. In the first, the data are subjected to an N-point correlation function analysis, and in the second to a power spectrum analysis. We focus on large and intermediate scales (larger than about 3 degrees), and compare the observed data on these scales against Monte Carlo ensembles with WMAP-like properties. On the largest scales we find that the WMAP data contain too little structure overall; both the two-point and three-point correlation functions reject the model at the 3-sigma level. Even more importantly, we find clear asymmetries between pairs of hemispheres. The northern and western galactic hemispheres and the northern ecliptic hemisphere have much less large scale fluctuations than the simulated maps, whereas the southern and eastern galactic hemispheres and the southern ecliptic hemisphere show relatively stronger fluctuations. The same asymmetries are also found on intermediate scales, as measured by correlation functions at 3-5 degrees. Also, comparison of the hemisphere power spectra yields consistent results; the ratio of the northern to the southern ecliptic hemisphere power spectrum is found to be low in the multipole range l~2-35 at the 3-sigma confidence level. Finally, in order to check for systematics, we study the power spectra also from the COBE-DMR maps, and find similar asymmetries in those data.Keywords
All Related Versions
This publication has 0 references indexed in Scilit: