Detection of a non‐Gaussian spot in WMAP

By M.Cruz, E.Martinez-Gonzalez, P.Vielva, L.Cayon. 2004

305 citations recorded by the source corpus.

An extremely cold and big spot in the Wilkinson Microwave Anisotropy Probe (WMAP) 1-yr data is analysed. Our work is a continuation of a previous paper by Vielva et al. that reported the detection of non-Gaussianity, with a method based on the spherical Mexican hat wavelet (SMHW) technique. We study the spots at different thresholds on the SMHW coefficient maps, considering six estimators, namely the number of maxima, the number of minima, the numbers of hot and cold spots, and the number of pixels of those spots. At SMHW scales around 4° (10° on the sky), the data deviate from Gaussianity. The analysis is performed on all of the sky, the Northern and Southern hemispheres, and on four regions covering all of the sky. A cold spot at (b = -57°,l = 209°) is found to be the source of this non-Gaussian signature. We compare the spots of our data with 10 000 Gaussian simulations, and conclude that only around 0.2 per cent of them present such a cold spot. Excluding this spot, the remaining map is compatible with Gaussianity, and even the excess of kurtosis in the paper by Vielva et al. is found to be due exclusively to this spot. Finally, we study whether the spot causing the observed deviation from Gaussianity could be generated by systematics or foregrounds. None of them seem to be responsible for the non-Gaussian detection.

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Citations in the corpus

FIVE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE OBSERVATIONS: COSMOLOGICAL INTERPRETATION (2008, unknown): “…et al. 2004; Schwarz et al. 2004; Copi et al. 2006, 2007; Gordon et al. 2005; Bielewicz et al. 2005; Jaffe et al. 2005, 2006; Vielva et al. 2004; Cruz et al. 2005, 2006, 2007b,a; Cayón et al. 2005; Bridges et al. 2007; Wiaux et al. 2008; Räth et al. 2007; Land & Magueijo 2005b,a, 2007; Rakić…”
Extragalactic Radio Sources and the WMAP Cold Spot (2007, methodology): “The non-gaussianity of this extreme region has been scrutinized, (Cayon, Jun & Treaster 2005; Cruz et al. 2005, 2006, 2007) concluding that it cannot be explained by either foreground correction problems or the normal Gaussian fluctuations of the CMB.”
Hemispherical Power Asymmetry in the Third-Year Wilkinson Microwave Anisotropy Probe Sky Maps (2007, background): “…multipoles (de Oliveira-Costa et al. 2004; Eriksen et al. 2004a), 2) an apparent asymmetry in the distribution of fluctuation power in two opposing hemispheres (Eriksen et al. 2004b; Hansen et al. 2004), and 3) a peculiar cold spot in the southern hemisphere (Vielva et al. 2004; Cruz et al. 2005).”
Resolving the Hubble tension with new early dark energy (2020, background): “It is an intriguing possibility that such a feature in the CMB could be related to NEDE [69, 70]”
Some characterizations of the spherical harmonics coefficients for isotropic random fields (2006, background): “Key words and phrases Spherical Random Fields, Spherical Harmonics, Characterization of Gaussian Random Fields.”
Cosmology and Fundamental Physics with the Euclid Satellite (2012, methodology): “This has been mainly motivated by hints of anomalies in the cosmic microwave background (CMB) distribution observed on the full sky by the WMAP satellite [388, 1210, 359, 464] and Planck satellite [963, 964, 965, 966].”
INCREASING EVIDENCE FOR HEMISPHERICAL POWER ASYMMETRY IN THE FIVE-YEAR WMAP DATA (2009, background): “…violation of statistical isotropy in the WMAP data has grown very large, indeed (e.g., Bernui et al. 2006; Bielewicz et al. 2005; Copi et al. 2006; Cruz et al. 2005, 2006; Eriksen et al. 2004b,c, 2005; Jaffe et al. 2005, 2006; Mart́ınez-González et al. 2006; McEwen et al. 2008; Räth et al.…”
The non‐Gaussian cold spot in Wilkinson Microwave Anisotropy Probe: significance, morphology and foreground contribution (2006, methodology): “…alignment statistics (Wiaux et al. 2006); multivariate analysis (Dineen & Coles 2005); Minkowski functionals (Park 2004, Eriksen et al. 2004b); gradient and dispersion analyses (Chyzy et al. 2005) or wavelets (Vielva et al. 2004, Mukherjee & Wang 2004, Cruz et al. 2005, McEwen et al. 2005).”
Local Voids as the Origin of Large-Angle Cosmic Microwave Background Anomalies. I. (2006, background): “…between the quadrupole and the octopole (Tegmark et al. 2003; de Oliveira-Costa et al. 2004); an anomalously cold spot on angular scales 10 (Vielva et al. 2004; Cruz et al. 2005, 2006); and an asymmetry in the largeangle power between opposite hemispheres (Eriksen et al. 2004; Hansen et al. 2004).”
Evidence of Vorticity and Shear at Large Angular Scales in the WMAP Data: A Violation of Cosmological Isotropy? (2005, background): “In addition, Vielva et al. (2004) and Cruz et al. (2005) have detected a localised source of non-Gaussianity, in the form of a very cold spot on the sky of angular scale ∼ 10◦.”