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Volume 454, Number 2, August I 2006
APEX Special Booklet
Page(s) 409 - 414
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:20054243

A&A 454, 409-414 (2006)
DOI: 10.1051/0004-6361:20054243

On the cosmic microwave background large-scale angular correlations

A. Bernui, T. Villela, C. A. Wuensche, R. Leonardi and I. Ferreira

Instituto Nacional de Pesquisas Espaciais, Divisão de Astrofísica, Av. dos Astronautas 1758, 12227-010, São José dos Campos, SP - Brazil
    e-mail: [bernui;thyrso;alex;leonardi;ivan]@das.inpe.br

(Received 23 September 2005 / Accepted 16 January 2006)

Aims.We study the large-scale angular correlation signatures of the cosmic microwave background (CMB) temperature fluctuations from WMAP data in several spherical cap regions of the celestial sphere, outside the Kp0 or Kp2 cut-sky masks.
Methods.We applied a recently proposed method to CMB temperature maps to permit an accurate analysis of their angular correlations in the celestial sphere through the use of normalized histograms of the number of pairs of such objects with a given angular separation versus their angular separation. The method allows for a better comparison of the results from observational data with the expected CMB angular correlations of a statistically isotropic universe, computed from Monte-Carlo maps according to the WMAP best-fit $\Lambda$CDM model.
Results.We found that the already known, anomalous lack of large-scale power in full-sky CMB maps is mainly due to deficient angular correlations of a quadrupole-like signature. This result is robust with respect to frequency CMB maps and cut-sky masks. Moreover, we also confirm previous results regarding the uneven distribution in the sky of the large-scale power of WMAP data. In a bin-to-bin correlation analyses, measured by the full covariance matrix $\chi^2$ statistic, we found that the angular correlation signatures in opposite Galactic hemispheres are anomalous at a 98%-99% confidence level.

Key words: cosmology: large-scale structure of Universe -- cosmic microwave background -- cosmology: observations

© ESO 2006

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