Covariance of CMB anomalies

Abstract

Several unexpected features are observed at large angular scales in the CMB temperature anisotropy measurements by both WMAP and Planck. These include the lack of both variance and correlation, alignment of the lowest multipole moments with one another, hemispherical power asymmetry, and an odd-to-even parity excess. In this work, we study the statistics of eight representative large-angle CMB features in order to evaluate their covariance in LCDM. We do so using two sets of simulated CMB temperature maps; an ensemble of 100,000 simple Gaussian simulations, and 1000 Full Focal Plane (FFP) simulations provided by the Planck collaboration. In measuring feature probabilities, we pay particular attention to analysis choices, making sure that we can reproduce previous results in the literature, and explain differences where appropriate. The covariance structure we find is consistent with expectations given that many of the features studied are functions of the angular power spectrum. Notably, we find significant differences in the covariance entries associated with the quadrupole-octopole alignments derived from the Gaussian and FFP simulations. We additionally perform a principal component analysis to quantitatively gauge what combinations of features capture the most information about how simulation measurements vary, and to provide an alternative assessment of the ways in which the real sky is anomalous. The first four principal components explain about 90\% of the simulations' variance, with the first two roughly quantifying the lack of large-angle correlations, and the next two quantifying the phase-dependent anomalies (multipole alignments and power asymmetry). Though the results of this analysis are fairly unsurprising, its comprehensive approach serves to tie together a number of previous results, and will therefore provide context for future studies of large-angle anomalies.

arXiv comment22 pages, 8 figures, comments welcome. Code and data available at https://github.com/jessmuir/cmbanomcov_muir-adhikari-huterer . Minor edits to reflect published version, added Gruppuso 2017 citation

References in corpus (59)

• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters
• Planck 2015 results. XIII. Cosmological parameters
• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Preliminary Maps and Basic Results
• Planck 2013 results. I. Overview of products and scientific results
• 4-Year COBE DMR Cosmic Microwave Background Observations: Maps and Basic Results
• Asymmetries in the CMB anisotropy field
• Planck 2015 results. XI. CMB power spectra, likelihoods, and robustness of parameters
• The significance of the largest scale CMB fluctuations in WMAP
• Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Are There Cosmic Microwave Background Anomalies?
• Planck 2013 results. XXIII. Isotropy and statistics of the CMB
• Detection of non-Gaussianity in the WMAP 1-year data using spherical wavelets
• Is the low-l microwave background cosmic?
• Planck 2015 results. XVI. Isotropy and statistics of the CMB
• Suppressing the lower Multipoles in the CMB Anisotropies
• CMB Anomalies after Planck
• Multipole Vectors--a new representation of the CMB sky and evidence for statistical anisotropy or non-Gaussianity at 2<=l<=8
• Hemispherical power asymmetry in the three-year Wilkinson Microwave Anisotropy Probe sky maps
• On the large-angle anomalies of the microwave sky
• Planck 2015 results. IX. Diffuse component separation: CMB maps
• The Uncorrelated Universe: Statistical Anisotropy and the Vanishing Angular Correlation Function in WMAP Years 1-3
• Increasing evidence for hemispherical power asymmetry in the five-year WMAP data
• Planck 2013 results. XXVII. Doppler boosting of the CMB: Eppur si muove
• Fast estimation of polarization power spectra using correlation functions
• Spontaneous Isotropy Breaking: A Mechanism for CMB Multipole Alignments
• 2-Point Correlations in the COBE DMR 4-Year Anisotropy Maps
• Asymmetries in the local curvature of the WMAP data
• Power asymmetry in WMAP and Planck temperature sky maps as measured by a local variance estimator
• No large-angle correlations on the non-Galactic microwave sky
• Is the Universe odd?
• Anomalous parity asymmetry of the Wilkinson Microwave Anisotropy Probe power spectrum data at low multipoles
• Lack of large-angle TT correlations persists in WMAP and Planck
• Large-scale alignments from WMAP and Planck
• Assessing the effects of foregrounds and sky removal in WMAP
• Testable polarization predictions for models of CMB isotropy anomalies
• New constraints on Parity Symmetry from a re-analysis of the WMAP-7 low resolution power spectra
• Anomalous parity asymmetry of WMAP power spectrum data at low multpoles: is it cosmological or systematics?
• Bayesian Power Spectrum Analysis of the First-Year WMAP data
• Correlating anomalies of the microwave sky: The Good, the Evil and the Axis
• Aspects of the Cosmic Microwave Background Dipole
• A low CMB variance in the WMAP data
• Cosmological Parameter Constraints as Derived from the Wilkinson Microwave Anisotropy Probe Data via Gibbs Sampling and the Blackwell-Rao Estimator
• On the significance of power asymmetries in Planck CMB data at all scales
• A comprehensive overview of the Cold Spot
• Missing Power vs low-l Alignments in the Cosmic Microwave Background: No Correlation in the Standard Cosmological Model
• Anomalous variance in the WMAP data and Galactic Foreground residuals
• Large-Angle CMB Suppression and Polarization Predictions
• Large-scale anomalies in the cosmic microwave background as signatures of non-Gaussianity
• Two-point Correlation Function of WMAP 9 year data
• Local variance asymmetries in Planck temperature anisotropy maps
• Alignments of parity even/odd-only multipoles in CMB
• Contamination cannot explain the lack of large-scale power in the cosmic microwave background radiation
• Microwave Background Polarization as a Probe of Large-Angle Correlations
• A comparison of CMB Angular Power Spectrum Estimators at Large Scales: the TT case
• Detectability of large-scale power suppression in the galaxy distribution
• Testing physical models for dipolar asymmetry with CMB polarization
• Probing Large-Angle Correlations with the Microwave Background Temperature and Lensing Cross Correlation
• CMB low multipole alignments in the $\mathbf{\Lambda }$CDM and Dipolar models
• CMB-S4 and the Hemispherical Variance Anomaly

Cited by in corpus (19)

• Challenges for $\Lambda$CDM: An update
• Planck 2018 results. VII. Isotropy and Statistics of the CMB
• Is the Observable Universe Consistent with the Cosmological Principle?
• Ginzburg-Landau Theory of Dark Energy: A Framework to Study Both Temporal and Spatial Cosmological Tensions Simultaneously
• Explaining Cosmological Anisotropy: Evidence for Causal Horizons from CMB data
• The Degree of Fine-Tuning in our Universe -- and Others
• Modeling the large-scale power deficit with smooth and discontinuous primordial spectra
• Lack-of-correlation anomaly in CMB large scale polarisation maps
• Joint Bayesian analysis of large angular scale CMB temperature anomalies
• Testing CMB Anomalies in E-mode Polarization with Current and Future Data
• Scale-dependent dipolar modulation and the quadrupole-octopole alignment in the CMB temperature
• Multipole vectors of completely random microwave skies for $l\le 50$
• Isotropic non-Gaussian $g_{\mathrm{NL}}$-like toy models that reproduce the cosmic microwave background anomalies
• The CMB cold spot under the lens: ruling out a supervoid interpretation
• Late-Time Anisotropy Sourced by a 2-Form Field Non-Minimally Coupled to Cold Dark Matter
• Is the lack of power anomaly in the CMB correlated with the orientation of the Galactic plane?
• CMB two-point angular correlation function in the Ellipsoidal Universe
• Phenomenology of Holography via Quantum Coherence on Causal Horizons
• Large-scale structure with superhorizon isocurvature dark energy