Detection of Dipole Modulation in CMB Temperature Anisotropy Maps from WMAP and Planck using Artificial Intelligence

Abstract

Breakdown of rotational invariance of the primordial power spectrum manifests in the statistical anisotropy of the observed Cosmic Microwave Background (CMB) radiation. Hemispherical power asymmetry in the CMB may be caused due to a dipolar modulation, indicating the presence of a preferred direction. Appropriately re-scaled local variance maps of the CMB temperature anisotropy data effectively encapsulate this dipolar pattern. As a first-of-its-kind method, we train Artificial Neural Networks (ANNs) with such local variances as input features to distinguish statistically isotropic CMB maps from dipole modulated ones. Our trained ANNs are able to predict components of the amplitude times the unit vector of the preferred direction for mixed sets of modulated and unmodulated maps, with goodness of fit ($R^2$) scores $>0.97$ for full sky, and $>0.96$ for partial sky coverage. On all observed foreground-cleaned CMB maps, the ANNs detect the dipolar modulation signal with overall consistent values of amplitudes and directions. This detection is significant at $97.21\%-99.38\%$ C.L. for all full sky maps, and at $98.34\%-100\%$ C.L. for all partial sky maps. Robustness of the signal holds across full and partial skies, various foreground cleaning methods, inpainting algorithms, instruments and all the different periods of observation for Planck and WMAP satellites. The significant and robust detection of the signal, in addition to the consistency of values of amplitude and directions, as found independent of any pre-existing methods, further mitigates the criticisms of look-elsewhere effects and a posteriori inferences for the preferred dipole direction in the CMB.

arXiv comment21 pages, 16 figures

References in corpus (62)

• 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
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results
• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Data Processing, Sky Maps, and Basic Results
• Aleatoric and Epistemic Uncertainty in Machine Learning: An Introduction to Concepts and Methods
• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Foreground Emission
• Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Temperature Analysis
• MASTER of the CMB Anisotropy Power Spectrum: A Fast Method for Statistical Analysis of Large and Complex CMB Data Sets
• Asymmetries in the CMB anisotropy field
• A high resolution foreground cleaned CMB map from WMAP
• The significance of the largest scale CMB fluctuations in WMAP
• The axis of evil
• Is the low-l microwave background cosmic?
• Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Galactic Foreground Emission
• Planck 2018 results. IV. Diffuse component separation
• Testing the cosmological principle of isotropy: local power spectrum estimates of the WMAP data
• Planck intermediate results. LVII. Joint Planck LFI and HFI data processing
• Planck 2013 results. XII. Component separation
• Hemispherical power asymmetry in the three-year Wilkinson Microwave Anisotropy Probe sky maps
• 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
• COSMOPOWER: emulating cosmological power spectra for accelerated Bayesian inference from next-generation surveys
• 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
• The Hot and Cold Spots in the WMAP Data are Not Hot and Cold Enough
• A deep learning approach to cosmological dark energy models
• Lack of large-angle TT correlations persists in WMAP and Planck
• Analysing the 21cm signal from the Epoch of Reionization with artificial neural networks
• Reconstructing Functions and Estimating Parameters with Artificial Neural Networks: A Test with the Hubble Parameter and SNe Ia
• Anomalous parity asymmetry of WMAP power spectrum data at low multpoles: is it cosmological or systematics?
• 2-point anisotropies in WMAP and the Cosmic Quadrupole
• A low CMB variance in the WMAP data
• Explaining Cosmological Anisotropy: Evidence for Causal Horizons from CMB data
• Testing Isotropy of Cosmic Microwave Background Radiation
• Parity Asymmetry in the CMBR Temperature Power Spectrum
• Directional Variations of Cosmological Parameters from the Planck CMB Data
• Neural Network Reconstruction of Late-Time Cosmology and Null Tests
• Full-sky Cosmic Microwave Background Foreground Cleaning Using Machine Learning
• Planck CMB Anomalies: Astrophysical and Cosmological Secondary Effects and the Curse of Masking
• Anomalous variance in the WMAP data and Galactic Foreground residuals
• Directional dependence of CMB parity asymmetry
• Signals of Statistical Anisotropy in WMAP Foreground-Cleaned Maps
• On the proper kinetic quadrupole CMB removal and the quadrupole anomalies
• BAMBI: blind accelerated multimodal Bayesian inference
• Low-l CMB Analysis and Inpainting
• Accelerated Bayesian inference using deep learning
• Local variance asymmetries in Planck temperature anisotropy maps
• Observational cosmology with Artificial Neural Networks
• Testing the Dipole Modulation Model in CMBR
• Recovering the CMB Signal with Machine Learning
• North-South non-Gaussian asymmetry in PLANCK CMB maps
• Relating the inhomogeneous power spectrum to the CMB hemispherical anisotropy
• Artificial Neural Network in Cosmic Landscape
• Using Artificial Neural Networks to extract the 21-cm Global Signal from the EDGES data
• Isotropy statistics of CMB hot and cold spots
• Scale-dependent dipolar modulation and the quadrupole-octopole alignment in the CMB temperature
• Estimation of Full Sky Power Spectrum between Intermediate to Large Angular Scales from Partial Sky CMB Anisotropies using Artificial Neural Network
• An Unbiased Estimator of the Full-sky CMB Angular Power Spectrum at Large Scales using Neural Networks
• Level correlations of the CMB temperature angular power spectrum

Cited by in corpus (4)

• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• Probing cosmic isotropy in the Local Universe
• ParamANN: A Neural Network to Estimate Cosmological Parameters for $\Lambda$CDM Universe Using Hubble Measurements
• Reconstruction of full sky CMB $\mathbf{E}$ and $\mathbf{B}$ modes spectra removing $\mathbf{E}$-to-$\mathbf{B}$ leakage from partial sky using deep learning