Quadrant asymmetry in the angular distribution of cosmic microwave background in the Planck satellite data

¹ Università di Roma “Tor Vergata”Dipartimento di Fisica, 00133 Rome, Italy
e-mail: larissa.santos@roma2.infn.it
² INFN, Sezione di Roma Tor Vergata, 00133 Rome, Italy
³ Instituto Nacional de Pesquisas Espaciais - INPE, Divisão de Astrofísica, 12227-010 São José dos Campos, SP, Brazil

Received: 29 October 2013
Accepted: 29 July 2014

Abstract

Some peculiar features found in the angular distribution of the cosmic microwave background (CMB) measured by the Wilkinson Microwave Anisotropy Probe (WMAP) deserve further investigation. Among these peculiar features is the quadrant asymmetry, which is likely related to the north-south asymmetry. In this paper, we aim to extend the analysis of the quadrant asymmetry in the ΛCDM framework to the Planck foreground-cleaned maps, using the mask provided by Planck team. We compute the two-point correlation function (TPCF) from each quadrant of the Planck CMB sky maps, and compare the result with 1000 Monte Carlo (MC) simulations generated assuming the ΛCDM best-fit power spectrum. We detect the presence of an excess of power in the southeastern quadrant (SEQ) and a significant lack of power in the northeastern quadrant (NEQ) in the Planck data. Asymmetries between the SEQ and the other three quadrants (southwestern quadrant (SWQ), northwestern quadrant (NWQ), and NEQ) are each in disagreement with an isotropic sky at a 95% confidence level. Furthermore, by rotating the Planck temperature sky map with respect to z direction, we showed the rotation angle where the TPCF of the SEQ has its maximal power. Our analysis of the Planck foreground-cleaned maps shows that there is an excess of power in the TPCF in the SEQ and a significant lack of power in the NEQ when compared with simulations. This asymmetry is anomalous when considering the ΛCDM framework.