Wednesday, March 20, 2013

1303.4727 (A. Rassat et al.)

Removal of two large scale Cosmic Microwave Background anomalies after subtraction of the Integrated Sachs Wolfe effect    [PDF]

A. Rassat, J. -L. Starck, F. -X. Dupe
Although there is currently a debate over the significance of the claimed large scale anomalies in the Cosmic Microwave Background (CMB), their existence is not totally dismissed. In parallel to the debate over their statistical significance, recent work has also focussed on masks and secondary anisotropies as potential sources of these anomalies. In this work we investigate simultaneously the impact of masked regions as well the integrated Sachs-Wolfe (ISW) effect, the secondary anisotropy most likely to affect these anomalies. Our work is an update of both Francis & Peacock 2010 and Kim et al. 2012. We aim to identify trends in CMB data from different years and with different masks treatments. We reconstruct the ISW signal due to 2MASS and NVSS galaxies, effectively reconstructing the low-z ISW signal out to z ~ 1. We account for missing data using sparse inpainting techniques of Abrial et al. 2008, Starck, Murtagh & Fadili 2010 and Starck, Fadili & Rassat 2013. We test sparse inpainting of the CMB, Large Scale Structure and ISW and find it constitutes a bias-free reconstruction method suitable to study large-scale statistical isotropy and the ISW effect. We focus on three large-scale CMB anomalies: the low quadrupole, the quadrupole/octopole alignment and the octopole planarity. After sparse inpainting, the low quadrupole becomes more anomalous, whilst the quadrupole/octopole alignment becomes less anomalous. After subtraction of the ISW, the trend is that both the low quadrupole and the quadrupole/octopole alignment are no longer statistically significant. Our results also suggest that both of these previous anomalies may be due to the quadrupole alone. The octopole planarity significance is reduced after inpainting and after ISW subtraction, though it was very anomalous to start with.
View original: http://arxiv.org/abs/1303.4727

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