2-point anisotropies in WMAP and the Cosmic Quadrupole

Abstract

Large-scale modes in the temperature anisotropy power spectrum C_l measured by the Wilkinson Microwave Anisotropy Probe (WMAP), seem to have lower amplitudes (C_2, C_3 and C_4) than that expected in the so called concordance LCDM model. In particular, the quadrupole C_2 is reported to have a smaller value than allowed by cosmic variance. This has been interpreted as a possible indication of new physics. In this paper we re-analyse the WMAP data using the 2-point angular correlation and its higher-order moments. This method, which requires a full covariance analysis, is more direct and provides better sampling of the largest modes than the standard harmonic decomposition. We show that the WMAP data is in good agreement (~ 30% probability) with a LCDM model when the WMAP data is considered as a particular realization drawn from a set of realistic LCDM simulations with the corresponding covariance. This is also true for the higher-order moments, shown here up to 6th order, which are consistent with the Gaussian hypothesis. The sky mask plays a major role in assessing the significance of these agreements. We recover the best fit model for the low-order multipoles based on the 2-point correlation with different assumptions for the covariance. Assuming that the observations are a fair sample of the true model, we find C_2 = 123 +/- 233, C_3= 217 +/- 241 and C_4 = 212 +/- 162 (in mu K^2). The errors increase by about a factor of 5 if we assume the \lcdm model. If we exclude the Galactic plane |b|<30 from our analysis, we recover very similar values within the errors (ie C_2=172, C_3= 89, C_4=129). This indicates that the Galactic plane is not responsible for the lack of large-scale power in the WMAP data.

arXiv comment11 pages, 23 figs, matches version accepted for publication in MNRAS. Additional tests with 2000 more simulations presented, including histogram of chi2 values. Probability for LCDM shown to be as large as ~30%. Main conclusions unchanged

References in corpus (11)

• A Line of Sight Approach to Cosmic Microwave Background Anisotropies
• Suppressing the lower Multipoles in the CMB Anisotropies
• Analysis of Systematic Effects and Statistical Uncertainties in Angular Clustering of Galaxies from Early SDSS Data
• Microwave Emission at High Galactic Latitudes
• Is the Low CMB Quadrupole a Signature of Spatial Curvature?
• 2-Point Correlations in the COBE DMR 4-Year Anisotropy Maps
• Non-Gaussianity of the derived maps from the first-year WMAP data
• Band Power Spectra in the COBE DMR 4-Year Anisotropy Maps
• 3-point temperature anisotropies in WMAP: Limits on CMB non-Gaussianities and non-linearities
• Three-Point Correlations in the COBE-DMR Two-Year Anisotropy Maps
• 2-Point Moments in Cosmological Large Scale Structure: I. Theory and Comparison with Simulations

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