Journal Article

Signals of statistical anisotropy in <i>WMAP</i> foreground-cleaned maps

Pramoda Kumar Samal, Rajib Saha, Pankaj Jain and John P. Ralston

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 396, issue 1, pages 511-522
Published in print June 2009 | ISSN: 0035-8711
Published online June 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.14728.x
Signals of statistical anisotropy in WMAP foreground-cleaned maps

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Recently, a symmetry-based method to test for statistical isotropy of the cosmic microwave background was developed. We apply the method to template-cleaned 3- and 5-years Wilkinson Microwave Anisotropy Probe-Differencing Assembly maps. We examine a wide range of angular multipoles from 2 < l < 300. The analysis detects statistically significant signals of anisotropy inconsistent with an isotropic cosmic microwave background in some of the foreground-cleaned maps. We are unable to resolve whether the anomalies have a cosmological, local astrophysical or instrumental origin. Assuming the anisotropy arises due to residual foreground contamination, we estimate the residual foreground power in the maps. For the W-band maps, we also find a highly improbable degree of isotropy we cannot explain. We speculate that excess isotropy may be caused by faulty modelling of detector noise.

Keywords: methods: data analysis; cosmic microwave background; cosmology: miscellaneous

Journal Article.  6293 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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