Needlet Detection of Features in WMAP CMB Sky and the Impact on Anisotropies and Hemispherical Asymmetries

Abstract

We apply spherical needlets to the Wilkinson Microwave Anisotropy Probe 5-year cosmic microwave background (CMB) dataset, to search for imprints of non-isotropic features in the CMB sky. We use the needlets localization properties to resolve peculiar features in the CMB sky and to study how these features contribute to the anisotropy power spectrum of the CMB. In addition to the now well-known "cold spot" of the CMB map in the southern hemisphere, we also find two hot spots at greater than 99% confidence level, again in the southern hemisphere and closer to the Galactic plane. While the cold spot contributes to the anisotropy power spectrum in the multipoles between l=6 to l=33, the hot spots are found to be dominating the anisotropy power in the range between l=6 and l=18. Masking both the cold and the two hot spots results in a reduction by about 15% in the amplitude of the angular power spectrum of CMB around l=10. The resulting changes to the cosmological parameters when the power spectrum is estimated masking these features (in addition to the WMAP team's KQ85 mask) are within the 1$\sigma$ errors published with the WMAP mask only. We also study the asymmetry between the angular power spectra evaluated on the northern and southern hemispheres. When the features detected by needlets are masked, we find that the difference in the power, measured in terms of the anisotropy variance between l=4 and l=18, is reduced by a factor 2. We make available a mask related to needlet features for more detailed studies on asymmetries in the CMB anisotropy sky.

arXiv comment12 pages, 12 figures; masks available at http://www.fisica.uniroma2.it/~cosmo/masks

References in corpus (25)

• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• Detection of non-Gaussianity in the WMAP 1-year data using spherical wavelets
• A model of diffuse Galactic Radio Emission from 10 MHz to 100 GHz
• 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
• The non-Gaussian Cold Spot in the 3-year WMAP data
• Power spectrum estimation from high-resolution maps by Gibbs sampling
• Integrated Sachs-Wolfe effect from the cross correlation of WMAP3 year and the NRAO VLA sky survey data: New results and constraints on dark energy
• Spherical Needlets for CMB Data Analysis
• Wavelets, ridgelets and curvelets on the sphere
• Asymmetries in the local curvature of the WMAP data
• The Hot and Cold Spots in the WMAP Data are Not Hot and Cold Enough
• Exact reconstruction with directional wavelets on the sphere
• Correspondence principle between spherical and Euclidean wavelets
• Detection of the ISW effect and corresponding dark energy constraints
• Detection of the ISW effect and corresponding dark energy constraints made with directional spherical wavelets
• Constraints on CPT violation from WMAP three year polarization data: a wavelet analysis
• Global universe anisotropy probed by the alignment of structures in the cosmic microwave background
• A high-significance detection of non-Gaussianity in the WMAP 3-year data using directional spherical wavelets
• Foreground Subtraction of Cosmic Microwave Background Maps using WI-FIT (Wavelet based hIgh resolution Fitting of Internal Templates)
• Alignment and signed-intensity anomalies in WMAP data
• Search for non-Gaussianity in pixel, harmonic and wavelet space: compared and combined
• Blind component separation in wavelet space. Application to CMB analysis
• Non-Gaussianity analysis on local morphological measures of WMAP data
• Cosmic Microwave Background Anisotropy from Nonlinear Structures in Accelerating Universes

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