Asymmetry of the CMB map: local and global anomalies

Abstract

We investigate the sources of parity asymmetry in the CMB temperature maps using a pixel domain approach. We demonstrate that this anomaly is mainly associated with the presence of two pairs of high asymmetry regions. The first pair of peaks with Galactic coordinates $(l,b)=(212^{\circ },-21^{\circ })$ and $(32^{\circ },21^{\circ })$ is associated with the Northern Galactic Spur and the direction of the dipole modulation of the power spectrum of the CMB anisotropy. The other pair ($(l,b)=(332^{\circ },-8^{\circ })$ and $(152^{\circ },8^{\circ })$) is located within the Galactic plane (the Galactic Cold Spot and its antipodal partner). Similar asymmetric peaks, but with smaller amplitudes, belong to the WMAP/Planck Cold Spot and its partner in the Northern Galactic Spur. These local anomalies increase the odd-multipole power to a level consistent with Gaussian simulations. In contrast, the deficit of symmetric peaks is accompanied by a deficit in the even-multipole power and is the source of the parity asymmetry of the CMB temperature maps at the level of about 3 sigma. We also evaluate the influence of the quadrupole, which is another source of the even-multipole deficit. If the low quadrupole is an intrinsic feature of the theoretical model, it will reduce the significance of the parity asymmetry to around the 2 sigma level. We also investigate the relationship between the asymmetry of the power spectrum and the level of the parity asymmetry in the framework of a model with dipole modulation of a statistically uniform Gaussian signal. We show that these two anomalies are innately linked to each other.

15 pages, 10 figures

References in corpus (5)

• Hemispherical power asymmetry in the three-year Wilkinson Microwave Anisotropy Probe sky maps
• Power asymmetry in WMAP and Planck temperature sky maps as measured by a local variance estimator
• Fingerprints of Galactic Loop I on the Cosmic Microwave Background
• New constraints on Parity Symmetry from a re-analysis of the WMAP-7 low resolution power spectra
• Symmetry and anti-symmetry of the CMB anisotropy pattern

Cited by in corpus (5)

• Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies
• Finding origins of CMB anomalies in the inflationary quantum fluctuations
• Hubble tensions: a historical statistical analysis
• Missing large-angle correlations versus even-odd point-parity imbalance in the cosmic microwave background
• Probing CMB Polarization Gaussianity with the Statistics of Unpolarized Points: Non-Gaussianity of Planck Data and Prospects for Future B-Mode Measurements