Hemispherical Power Asymmetry in the Third-Year Wilkinson Microwave Anisotropy Probe Sky Maps

By H. Eriksen, A. Banday, K. G'orski, F. Hansen, P. Lilje. 2007

259 citations recorded by the source corpus.

We consider the issue of hemispherical power asymmetry in the third-year WMAP data, adopting a previously introduced modulation framework. Computing both frequentist probabilities and Bayesian evidences, we find that the model consisting of an isotropic CMB sky modulated by a dipole field gives a substantially better fit to the observations than the purely isotropic model, even when accounting for the larger prior volume. For the ILC map, the Bayesian log-evidence difference is ~1.8 in favor of the modulated model, and the raw improvement in maximum log likelihood is 6.1. The best-fit modulation dipole axis points toward (l, b) = (225°, -27°), and the modulation amplitude is 0.114, in excellent agreement with the results from the first-year analyses. The frequentist probability of obtaining such a high modulation amplitude in an isotropic universe is ~1%. These results are not sensitive to data set or sky cut. Thus, the statistical evidence for a power asymmetry anomaly is both substantial and robust, although not decisive, for the currently available data. Increased sky coverage through better foreground handling and full-sky and high-sensitivity polarization maps may shed further light on this issue.

Subfields: Astronomy and Astrophysics, Oceanography

View Paper: https://www.semanticscholar.org/paper/27b8c8cbbcc16a64e1dd3f7883656a5797f4118b

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. E. Komatsu
2. A. Banday
3. K. G'orski
4. H. Eriksen
5. David N. Spergel
6. Mark Halpern
7. C. Bennett
8. J. Weiland

In Oceanography

1. F. Hansen
2. A. Banday
3. H. Eriksen
4. K. G'orski
5. P. Lilje
6. J. Hoftuft
7. E. Komatsu
8. Yashar Akrami

Citations in the corpus

• SEVEN-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP ) OBSERVATIONS: ARE THERE COSMIC MICROWAVE BACKGROUND ANOMALIES? (2010, methodology): “Eriksen et al. (2007) used this approach to search for a dipole power asymmetry in low-resolution three-year WMAP data and a statistical significance of ∼ 99% was claimed.”
• FIVE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE OBSERVATIONS: COSMOLOGICAL INTERPRETATION (2008, unknown): “…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 et al. 2004; Schwarz et al. 2004; Copi et al. 2006, 2007; Gordon et al. 2005; Bielewicz et al. 2005; Jaffe et al.…”
• POWER ASYMMETRY IN COSMIC MICROWAVE BACKGROUND FLUCTUATIONS FROM FULL SKY TO SUB-DEGREE SCALES: IS THE UNIVERSE ISOTROPIC? (2008, background): “Some of these have been confirmed again in the 3 and 5 year data (Hinshaw et al. 2007; Spergel et al. 2006; Cruz et al. 2006; McEwen et al. 2006; Eriksen et al 2007; Pietrobon et al. 2008).”
• 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).”
• SEVEN-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP) OBSERVATIONS: COSMOLOGICAL INTERPRETATION (2010, methodology): “…et al. 2010) to measure the low-l TT power spectrum in l = 2 − 32, and calculate the likelihood using the Gibbs sampling and Blackwell-Rao (BR) estimator (Jewell et al. 2004; Wandelt 2003; Wandelt et al. 2004; O’Dwyer et al. 2004; Eriksen et al. 2004, 2007a,b; Chu et al. 2005; Larson et al. 2007).”
• Fundamental physics with the Square Kilometre Array (2018, methodology): “…components of angular correlations of CMB anisotropies with WMAP and Planck data on large scales (Hansen et al., 2004; Gordon et al., 2005; Eriksen et al., 2007; Gordon, 2007; Planck Collaboration et al., 2014b; Akrami et al., 2014; Planck Collaboration et al., 2016e,c; Aiola et al.,…”
• INCREASING EVIDENCE FOR HEMISPHERICAL POWER ASYMMETRY IN THE FIVE-YEAR WMAP DATA (2009, methodology): “Note that this approximation was explicitly validated by Eriksen et al. (2007b) for the 3-year WMAP data, which have higher instrumental noise than the 5-year data.”