Local bandpower diagnostics for the hemispherical power asymmetry in CMB E-mode polarization

Abstract

We present local bandpower diagnostics that test whether a candidate dipolar modulation in E-mode polarization data originates in the cosmic microwave background (CMB) itself rather than in noise or systematics. The target is the hemispherical power asymmetry (HPA), one of the most persistent large-scale anomalies in the CMB temperature field; polarization offers an independent probe of its origin, but at Planck sensitivity the polarized sky is noise-dominated. Local power is estimated in overlapping patches on the masked sky, with E-to-B leakage corrected through standard pseudo-$C_{\ell }$ deconvolution, and dipole directions are fitted independently to the two Planck half-mission maps, which share the same sky but carry independent noise. Tight directional agreement indicates a CMB-level signal, although it cannot distinguish a real modulation from a chance CMB fluctuation. Applied to Planck PR3 Commander data at $\ell =15$-$40$, the half-mission directions are separated by $8.7^{\circ }$, a closer agreement than in any of the 300 isotropic simulations ($p<0.33\%$), and lie near the temperature HPA axis. The coherence appears only in EE, vanishes without leakage correction, and is corroborated by a cross-spectrum check. LiteBIRD, with substantially higher polarization sensitivity, is a natural next application.

References in corpus (25)

• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• Planck 2018 results. X. Constraints on inflation
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results
• Planck 2018 results. I. Overview and the cosmological legacy of Planck
• 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
• The significance of the largest scale CMB fluctuations in WMAP
• Detection of non-Gaussianity in the WMAP 1-year data using spherical wavelets
• Planck 2018 results. VII. Isotropy and Statistics of the CMB
• Planck 2015 results. XVI. Isotropy and statistics of the CMB
• Planck 2018 results. IV. Diffuse component separation
• A unified pseudo-$C_{\ell }$ framework
• CMB Anomalies after Planck
• Testing the cosmological principle of isotropy: local power spectrum estimates of the WMAP data
• Increasing evidence for hemispherical power asymmetry in the five-year WMAP data
• Estimators for CMB Statistical Anisotropy
• The non-Gaussian Cold Spot in the 3-year WMAP data
• A Hemispherical Power Asymmetry from Inflation
• Analysis of CMB polarization on an incomplete sky
• Power asymmetry in WMAP and Planck temperature sky maps as measured by a local variance estimator
• CMB EB and TB cross-spectrum estimation via pseudo-spectrum techniques
• Expected dipole asymmetry in CMB polarization
• Hemispherical Power Asymmetry in intensity and polarization for Planck PR4 data
• A Pixel Space Method for Testing Dipole Modulation in the CMB Polarization
• CMB Polarization by the Asymmetric Template of Scalar Perturbations