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Signals of statistical anisotropy in WMAP foreground-cleaned maps

Kumar Samal, Pramoda
Saha, Rajib
Jain, Pankaj
Ralston, John P.
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Abstract
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.
Description
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2008 The Authors. Journal compilation © 2009 RAS. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date
2009-06-03
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Oxford University Press
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Keywords
Methods: data analysis, Cosmic microwave background, Cosmology: miscellaneous
Citation
Pramoda Kumar Samal, Rajib Saha, Pankaj Jain, John P. Ralston, Signals of statistical anisotropy in WMAP foreground-cleaned maps, Monthly Notices of the Royal Astronomical Society, Volume 396, Issue 1, June 2009, Pages 511–522, https://doi.org/10.1111/j.1365-2966.2009.14728.x.
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