Signals of statistical anisotropy in WMAP foreground-cleaned maps |
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| Authors: | Pramoda Kumar Samal Rajib Saha Pankaj Jain John P Ralston |
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| Institution: | Department of Physics, Indian Institute of Technology, Kanpur, U.P. 208016, India;Jet Propulsion Laboratory, M/S 169-327, 4800 Oak Grove Drive, Pasadena, CA 91109, USA;California Institute of Technology, Pasadena, CA 91125, USA;Department of Physics &Astronomy, University of Kansas, Lawrence, KS 66045, USA |
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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. |
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| Keywords: | methods: data analysis cosmic microwave background cosmology: miscellaneous |
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