TY - JOUR
T1 - Understanding the WMAP cold spot mystery
AU - Nasselski, Pavel
AU - Christensen, Per Rex
AU - Coles, P.
AU - Verkhodanov, O.
AU - Novikov, Igor Dmitrievich
AU - Kim, Ja.
PY - 2010/4
Y1 - 2010/4
N2 - The Cold Spot (CS) at galactic coordinates (b = -57°, l = 209°) was discovered in the WilkinsonMicrowave Anisotropy Probe (WMAP)data as a cosmic background anomaly. In order to assess the cosmological significance of the Spot, we examine its properties using the cluster analysis of the local extrema in the cosmic microwave background (CMB) signal. We also check the hypothesis that the CMB signal has a non-Gaussian tail, localized in the low-multipole components. We constructed a linear filter, dividing the signal into two parts: non-Gaussian and Gaussian. Using the filter scale as a variable, we can maximize the skewness and kurtosis of the smoothed signal and minimize these statistics. We discovered that the shape of the CS is formed primarily by the components of the CMB signal represented by the multipoles between 10 ≤ ℓ ≤ 20, with a corresponding angular scale of about 5°-10°. This signal leads to the modulation of the CMB on the whole sky, clearly seen at {phipe}b{phipe} > 30° in both the ILC andWCM maps, rather than in a single localized feature. After subtraction of this modulation, the remaining part of the CMB signal appears to be consistent with statistical homogeneity and Gaussianity. We therefore infer that the mystery of the WMAP Cold Spot reflects directly the peculiarities of low multipoles of the CMB signal, rather than a single local (isolated) defect or the manifestations of a globally anisotropic cosmology.
AB - The Cold Spot (CS) at galactic coordinates (b = -57°, l = 209°) was discovered in the WilkinsonMicrowave Anisotropy Probe (WMAP)data as a cosmic background anomaly. In order to assess the cosmological significance of the Spot, we examine its properties using the cluster analysis of the local extrema in the cosmic microwave background (CMB) signal. We also check the hypothesis that the CMB signal has a non-Gaussian tail, localized in the low-multipole components. We constructed a linear filter, dividing the signal into two parts: non-Gaussian and Gaussian. Using the filter scale as a variable, we can maximize the skewness and kurtosis of the smoothed signal and minimize these statistics. We discovered that the shape of the CS is formed primarily by the components of the CMB signal represented by the multipoles between 10 ≤ ℓ ≤ 20, with a corresponding angular scale of about 5°-10°. This signal leads to the modulation of the CMB on the whole sky, clearly seen at {phipe}b{phipe} > 30° in both the ILC andWCM maps, rather than in a single localized feature. After subtraction of this modulation, the remaining part of the CMB signal appears to be consistent with statistical homogeneity and Gaussianity. We therefore infer that the mystery of the WMAP Cold Spot reflects directly the peculiarities of low multipoles of the CMB signal, rather than a single local (isolated) defect or the manifestations of a globally anisotropic cosmology.
U2 - 10.1134/S199034131002001X
DO - 10.1134/S199034131002001X
M3 - Journal article
SN - 1990-3413
VL - 65
SP - 101
EP - 120
JO - Astrophysical Bulletin
JF - Astrophysical Bulletin
IS - 2
ER -