Das, Santanu ; Mitra, Sanjit ; Rotti, Aditya ; Pant, Nidhi ; Souradeep, Tarun (2016) Statistical isotropy violation in WMAP CMB maps resulting from non-circular beams Astronomy & Astrophysics, 591 . No pp. given. ISSN 1432-0746
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Official URL: http://www.aanda.org/articles/aa/abs/2016/07/aa241...
Related URL: http://dx.doi.org/10.1051/0004-6361/201424164
Abstract
Statistical isotropy (SI) of cosmic microwave background (CMB) fluctuations is a key observational test to validate the cosmological principle underlying the standard model of cosmology. While a detection of SI violation would have immense cosmological ramification, it is important to recognise their possible origin in systematic effects of observations. The WMAP seven year (WMAP-7) release claimed significant deviation from SI in the bipolar spherical harmonic (BipoSH) coefficients All20 and Al-2l20>. Here we present the first explicit reproduction of the measurements reported in WMAP-7, confirming that beam systematics alone can completely account for the measured SI violation. The possibility of such a systematic origin was alluded to in WMAP-7 paper itself and other authors but not as explicitly so as to account for it accurately. We simulate CMB maps using the actual WMAP non-circular beams and scanning strategy. Our estimated BipoSH spectra from these maps match the WMAP-7 results very well. It is also evident that only a very careful and adequately detailed modelling, as carried out here, can conclusively establish that the entire signal arises from non-circular beam effect. This is important since cosmic SI violation signals are expected to be subtle and dismissing a large SI violation signal as observational artefact based on simplistic plausibility arguments run the serious risk of “throwing the baby out with the bathwater.
Item Type: | Article |
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Source: | Copyright of this article belongs to EDP Sciences. |
ID Code: | 107546 |
Deposited On: | 26 Dec 2017 07:04 |
Last Modified: | 26 Dec 2017 07:04 |
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