Non-Gaussian signatures in the temperature fluctuation observed by the Wilkinson Microwave Anisotropy Probe

By Chan-Gyung Park. 2003

151 citations recorded by the source corpus.

We present results from a test for the Gaussianity of the whole sky subdegree-scale cosmic microwave background (CMB) temperature anisotropy measured by the Wilkinson Microwave Anisotropy Probe (WMAP). We calculate the genus from the foreground-subtracted and Kp0-masked WMAP maps and measure the genus shift parameters defined at negative and positive threshold levels (Δv - and Δv + ) and the asymmetry parameter (Ag) to quantify the deviation from the Gaussian relation. At WMAP Q, V and W bands, the genus and genus-related statistics imply that the observed CMB sky is consistent with a Gaussian random phase field. However, from the genus measurement on the Galactic northern and southern hemispheres, we have found two non-Gaussian signatures at the W-band resolution (0.35 scale), i.e. the large difference of genus amplitudes between the north and the south and the positive genus asymmetry in the south, which are statistically significant at 2.6σ and 2.4σ levels, respectively. The large genus amplitude difference also appears in the WMAP Q- and V-band maps, deviating from the Gaussian prediction with a significance level of about 2σ. The probability that the genus curves show such a large genus amplitude difference exceeding the observed values at all Q, V and W bands in a Gaussian sky is only 1.4 per cent. Such non-Gaussian features are reduced as the higher Galactic cut is applied, but their dependence on the Galactic cut is weak. We discuss possible sources that can induce non-Gaussian features, such as the Galactic foregrounds, the integrated Sachs-Wolfe and the Sunyaev-Zel'dovich effects, and the reionization-induced low l-mode non-Gaussianity that are aligned along the Galactic plane. We conclude that CMB data with higher signal-to-noise ratio and an accurate foreground model are needed to understand the non-Gaussian signatures.

Subfields: Astronomy and Astrophysics, Global and Planetary Change, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/80dab5942d5c080d3a0121111264e5e10cc0172e

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Citations in the corpus

On the large-angle anomalies of the microwave sky (2005, unknown): “2003; Park 2004; Chiang etal.”
The non‐Gaussian cold spot in Wilkinson Microwave Anisotropy Probe: significance, morphology and foreground contribution (2006, unknown): “…2005, Tojeiro et al. 2005); structure 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…”
POWER ASYMMETRY IN WMAP AND PLANCK TEMPERATURE SKY MAPS AS MEASURED BY A LOCAL VARIANCE ESTIMATOR (2014, background): “…and is with current data sets generally found to be statistically significant at the 3σ–3.5σ level depending on the algorithm and angular scales under considerations (Park 2004; Eriksen et al. 2007; Hansen et al. 2009; Hoftuft et al. 2009; Axelsson et al. 2013; Planck Collaboration 2013d).”
Detection of Non-Gaussianity in the Wilkinson Microwave Anisotropy Probe First-Year Data Using Spherical Wavelets (2003, methodology): “Previous non-Gaussianity works on the WMAP data have reported some asymmetries between the northern and the southern hemispheres (Park 2004; Eriksen et al. 2004a).”
POWER ASYMMETRY IN COSMIC MICROWAVE BACKGROUND FLUCTUATIONS FROM FULL SKY TO SUB-DEGREE SCALES: IS THE UNIVERSE ISOTROPIC? (2008, background): “…as well as other statistical anomalies were confirmed by several other authors using other methods (de Oliveira-Costa et al. 2004; Tegmark et al. 2003; Park 2004; Vielva et al. 2004b; Eriksen et al. 2004b; Land & Magueijo 2005a,b; Larson & Wandelt 2004; McEwen et al. 2005; Hansen et al. 2004b,c).”
Testing for Non-Gaussianity in the Wilkinson Microwave Anisotropy Probe Data: Minkowski Functionals and the Length of the Skeleton (2004, methodology): “Here it is worth noticing that Park (2004) considered even smaller scales, since the maps were not explicitly smoothed at all, except for a small effect introduced by a stereographical projection.”
Local Voids as the Origin of Large-Angle Cosmic Microwave Background Anomalies. I. (2006, background): “Evidence for other forms of non-Gaussianity on large angular scales has also been reported (Chiang et al. 2004; Park 2004; Schwarz et al. 2004; Larson & Wandelt 2004).”
The Axis of Evil revisited (2006, unknown): “Reports of something awry have been obtained using a variety of techniques (e.g., Park (2004); Eriksen et al. (2004a); Hansen et al. (2004); Donoghue & Donoghue (2005); Land & Magueijo (2005a); Hansen et al. (2004); Eriksen et al. (2004b); Vielva et al. (2004)).”
FIVE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE OBSERVATIONS: COSMOLOGICAL INTERPRETATION (2008, unknown): “There have been many studies on non-Gaussian signatures in the WMAP data in various forms (Chiang et al. 2003, 2007; Naselsky et al. 2007; Park 2004; de Oliveira-Costa et al. 2004; Tegmark et al. 2003; Larson & Wandelt 2004; Eriksen et al. 2004; Eriksen et al. 2004; Eriksen et al. 2004, 2007a; Copi…”
On Foreground Removal from the Wilkinson Microwave Anisotropy Probe Data by an Internal Linear Combination Method: Limitations and Implications (2004, background): “Recent detections of non-Gaussianity (Chiang et al. 2003; Coles et al. 2004; Eriksen et al. 2004a; Naselsky et al. 2003; Park 2004; Vielva et al. 2004), the continuing debate over the low amplitude of large angular scale anisotropy (see, e.g., Efstathiou 2004), and a possible preferred direction or…”