Journal Article

Needlet bispectrum asymmetries in the <i>WMAP</i> 5-year data

Davide Pietrobon, Paolo Cabella, Amedeo Balbi, Robert Crittenden, Giancarlo De Gasperis and Nicola Vittorio

in Monthly Notices of the Royal Astronomical Society: Letters

Published on behalf of The Royal Astronomical Society

Volume 402, issue 1, pages L34-L38
Published in print February 2010 |
Published online February 2010 | e-ISSN: 1745-3933 | DOI:

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We apply the needlet formalism to the Wilkinson Microwave Anisotropy Probe 5-year data, looking for evidence of non-Gaussianity in the bispectrum of the needlet amplitudes. We confirm earlier findings of an asymmetry in the non-Gaussianity between the Northern and Southern Galactic hemispheres. We attempt to isolate which scales and geometrical configurations are most anomalous and find that the bispectrum is most significant on large scales and in the more co-linear configurations and also in the ‘squeezed’ configurations. However, these anomalies do not appear to affect the estimate of the non-linear parameter fNL, and we see no significant difference between its values measured in the two hemispheres.

Keywords: methods: data analysis; cosmic microwave background; early Universe

Journal Article.  3325 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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