2008/09/30 by D. Pietrobon, Davide Pietrobon, Alexandre Amblard +6 · 2 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Cosmology and Gravitation Theories #Radio Astronomy Observations and Technology #astro-ph
paper · pdf · doi:10.1103/physrevd.78.103504
published as Phys.Rev.D78:103504,2008 · 12 pages, 12 figures; masks available at http://www.fisica.uniroma2.it/~cosmo/masks
openalex publication_date 2008/11/06 · arxiv created 2008/11/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We apply spherical needlets to the Wilkinson Microwave Anisotropy Probe 5-year cosmic microwave background (CMB) data set, to search for imprints of nonisotropic 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 \ensuremathℓ=6 to \ensuremathℓ=33, the hot spots are found to be dominating the anisotropy power in the range between \ensuremathℓ=6 and \ensuremathℓ=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 \ensuremathℓ=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\ensuremathσ 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 \ensuremathℓ=4 and \ensuremathℓ=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.