Searching for hidden mirror symmetries in CMB fluctuations from WMAP 7 year maps

Abstract

We search for hidden mirror symmetries at large angular scales in the WMAP 7 year Internal Linear Combination map of CMB temperature anisotropies using global pixel based estimators introduced for this aim. Two different axes are found for which the CMB intensity pattern is anomalously symmetric (or anti-symmetric) under reflection with respect to orthogonal planes at the 99.84(99.96)% CL (confidence level), if compared to a result for an arbitrary axis in simulations without the symmetry. We have verified that our results are robust to the introduction of the galactic mask. The direction of such axes is close to the CMB kinematic dipole and nearly orthogonal to the ecliptic plane, respectively. If instead the real data are compared to those in simulations taken with respect to planes for which the maximal mirror symmetry is generated by chance, the confidence level decreases to 92.39 (76.65)%. But when the effect in question translates into the anomalous alignment between normals to planes of maximal mirror (anti)-symmetry and these natural axes mentioned. We also introduce the representation of the above estimators in the harmonic domain, confirming the results obtained in the pixel one. The symmetry anomaly is shown to be almost entirely due to low multipoles, so it may have a cosmological and even primordial origin. Contrary, the anti-symmetry one is mainly due to intermediate multipoles that probably suggests its non-fundamental nature. We have demonstrated that these anomalies are not connected to the known issue of the low variance in WMAP observations and we have checked that axially symmetric parts of these anomalies are small, so that the axes are not the symmetry ones.

18 pages, 10 figures, 2 tables. Consideration and discussion expanded, 5 figures and 1 table added, main conclusions unchanged

References in corpus (17)

• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• A Measurement of the Damping Tail of the Cosmic Microwave Background Power Spectrum with the South Pole Telescope
• Hemispherical power asymmetry in the three-year Wilkinson Microwave Anisotropy Probe sky maps
• The Uncorrelated Universe: Statistical Anisotropy and the Vanishing Angular Correlation Function in WMAP Years 1-3
• Global universe anisotropy probed by the alignment of structures in the cosmic microwave background
• New constraints on Parity Symmetry from a re-analysis of the WMAP-7 low resolution power spectra
• Alignment tests for low CMB multipoles
• Alignment and signed-intensity anomalies in WMAP data
• Is the CMB asymmetry due to the kinematic dipole?
• Constraints on the topology of the Universe derived from the 7-year WMAP data
• Power Asymmetries in the Cosmic Microwave Background Temperature and Polarization patterns
• Parity in the CMB: Space Oddity
• Pearson's random walk in the space of the CMB phases: evidence for parity asymmetry
• Large Scale Plane-Mirroring in the Cosmic Microwave Background WMAP5 Maps
• On Axial and Plane--Mirror Inhomogeneities in the WMAP3 Cosmic Microwave Background Maps
• Parametric tension between even and odd multipole data of WMAP power spectrum: unaccounted contamination or missing parameters?
• Maxwell's Multipole Vectors and the CMB

Cited by in corpus (15)

• Planck 2013 results. XXIII. Isotropy and statistics of the CMB
• Planck 2018 results. VII. Isotropy and Statistics of the CMB
• Planck 2015 results. XVI. Isotropy and statistics of the CMB
• Is the Observable Universe Consistent with the Cosmological Principle?
• CMB Maximum Temperature Asymmetry Axis: Alignment with Other Cosmic Asymmetries
• Cosmological model with local symmetry of very special relativity and constraints on it from supernovae
• Quadrupole--octopole alignment of CMB related to primordial power spectrum with dipolar modulation in anisotropic spacetime
• Hemispherical power asymmetries in the WMAP 7-year low-resolution temperature and polarization maps
• Studying the Peculiar Velocity Bulk Flow in a Sparse Survey of Type-Ia SNe
• CMB low multipole alignments in the $\mathbf{\Lambda }$CDM and Dipolar models
• Anisotropic cosmology and inflation from tilted Bianchi IX model
• A close examination of cosmic microwave background mirror-parity after Planck
• Parity in Planck full-mission CMB temperature maps
• Searching for Stringy Topologies in the Cosmic Microwave Background
• Homology reveals significant anisotropy in the cosmic microwave background