Searching for planar signatures in WMAP

Abstract

We search for planar deviations of statistical isotropy in the Wilkinson Microwave Anisotropy Probe (WMAP) data by applying a recently introduced angular-planar statistics both to full-sky and to masked temperature maps, including in our analysis the eect of the residual foreground contamination and systematics in the foreground removing process as sources of error. We conrm earlier ndings that full-sky maps exhibit anomalies at the planar (l) and angular ( ) scales (l, ) = (2, 5), (4, 7), and (6,8), which seem to be due to unremoved foregrounds since this features are present in the full-sky map but not in the masked maps. On the other hand, our test detects slightly anomalous results at the scales (l, ) = (10, 8) and (2,9) in the masked maps but not in the full-sky one, indicating that the foreground cleaning procedure (used to generate the full-sky map) could not only be creating false anomalies but also hiding existing ones. We also nd a signicant trace of an anomaly in the full-sky map at the scale (l, ) = (10, 5), which is still present when we consider galactic cuts of 18.3% and 28.4%. As regards the quadrupole ( = 2), we nd a coherent over-modulation over the whole celestial sphere, for all full-sky and cut-sky maps. Overall, our results seem to indicate that current CMB maps derived from WMAP data do not show signicant signs of anisotropies, as measured by our angular-planar estimator. However, we have detected a curious coherence of planar modulations at angular scales of the order of the galaxy's plane, which may be an indication of residual contaminations in the full-and cut-sky maps. PACS numbers: 98.80.-k, 98.70.Vc, 98.80.Es I. INTRODUCTIONThe statistical concordance model of the universe has now been established with unprecedent accuracy by the Wilkinson Microwave Anisotropy Probe (WMAP). The ve year dataset release of the WMAP team [1,2] has shown that to a very good extent the temperature eld of the cosmic microwave background radiation (CMB) obeys a Gaussian statistic with zero mean and a variance which is the same in every direction in the sky. At the same time, several dierent teams [3,4,5,6,7,8,9,10,11,12,13] have reported the detection of statistical peculiarities in this eld, mainly in the largest cosmological scales, which range from slightly to extremely unlikely within the framework of a Gaussian and statistically isotropic universe. Among these anomalies, the most conspicuous are the lack of power in the low-multipole sector and in the 2-point correlation function [3,6], the alignment of the quadrupole = 2 and the octopole = 3 [5,6,14], and the so-called north-south asymmetry [4,8,9,11,12,13,15,16,17,18,19]. Several attempts to explain away these statistical features in terms of known sources of microwave radiation or peculiarities of the instrument have been proposed, but have not yet produced a compelling explanation.If we put aside the hypotheses that these anomalies may possibly be due to some residual galactic contamination [20,21,22,23] or even to a systematic data analysis eect [...

A neural-network based estimator to search for primordial non-Gaussianity in Planck CMB maps

“…In [23] Planck team uses the analysis of the FFP6 simulations (Full Focal Plane 6, see [34] for details), exactly the same performed upon the real data, to provide important informations, or previsions, about the residual contamination expected for the four released Planck CMB maps. This type of contamination takes the following form on the simulation results: (1) the contamination on the Commander − Ruler is an under-subtracted free-free emission; (2) for the NILC and SEVEM it seems to be an over-subtracted thermal dust emission; and (3) for the SMICA there is an under-subtracted thermal dust emission. Therefore, the contamination is performed by adding a weighted foreground map to the MC CMB maps, when aiming to mimic the SMICA and Commander − Ruler residual maps, and by subtracting it from these maps if necessary to mimic the SEVEM and NILC residual maps.…”

“…Inflation not only explains the large-scale homogeneity and isotropy of the universe, but also provides a mechanism to produce primordial fluctuations in cosmic microwave background (CMB) radiation which follow a nearly Gaussian statistics, and where deviations from it characterises different classes of inflationary models [2][3][4][5][6][7]. Severe constraints for Gaussian deviations found in the latest Planck analysis strongly supports the simplest inflationary model based on a single minimally-coupled scalar field [8].…”

Angular-planar CMB power spectrum

“…On the other hand, the residual foreground can be an important source of contamination, and therefore deserves a careful analysis which is beyond the scope of the present work. In a companion paper we carry a more rigorous analysis of planar signature in CMB data in which the eect of the residual foreground will be estimated [29].…”

The scale of homogeneity in the local Universe with the ALFALFA catalogue

“…Besides, the projected isotropy of the Planck convergence map [19] and of the WISE galaxy map [20][21][22][23] have been also investigated without indications of a possible CP violation. The cosmic microwave background (CMB) radiation is also consistent with statistical isotropy at small angular scales [24][25][26], although some controversy exists at the largest scales [27][28][29][30][31][32][33][34][35].…”