Uncorrelated universe: Statistical anisotropy and the vanishing angular correlation function in WMAP years 1–3

Abstract

The large-angle (low-ℓ) correlations of the Cosmic Microwave Background (CMB) as reported by the Wilkinson Microwave Anisotropy Probe (WMAP) after their first year of observations exhibited statistically significant anomalies compared to the predictions of the standard inflationary big-bang model. We suggested then that these implied the presence of a solar system foreground, a systematic correlated with solar system geometry, or both. We re-examine these anomalies for the data from the first three years of WMAP's operation. We show that, despite the identification by the WMAP team of a systematic correlated with the equinoxes and the ecliptic, the anomalies in the firstyear Internal Linear Combination (ILC) map persist in the three-year ILC map, in all-but-one case at similar statistical significance. The three-year ILC quadrupole and octopole therefore remain inconsistent with statistical isotropy -they are correlated with each other (99.6%C.L.), and there are statistically significant correlations with local geometry, especially that of the solar system. The angular two-point correlation function at scales > 60 degrees in the regions outside the (kp0) galactic cut, where it is most reliably determined, is approximately zero in all wavebands and is even more discrepant with the best fit ΛCDM inflationary model than in the first-year data -99.97%C.L. for the new ILC map. The full-sky ILC map, on the other hand, has a non-vanishing angular two-point correlation function, apparently driven by the region inside the cut, but which does not agree better with ΛCDM. The role of the newly identified low-ℓ systematics is more puzzling than reassuring.

Detection of a supervoid aligned with the cold spot of the cosmic microwave background

“…Furthermore, the other CMB anomalies associated with large-angle correlations (Land & Magueijo 2005;Copi et al 2006Copi et al , 2013 should be revisited in light of these findings.…”

Missing power vs low-ℓ alignments in the cosmic microwave background: No correlation in the standard cosmological model

“…inv ( ,i) . Copi et al (2006) found thatn 2 ·n 3 = 0.962 for the TOH map. The corresponding values obtained from the analysis of the WMAP 7-year data is 0.937.…”

“…In the subsequent sections, to be conservative, we use S (3,3) = 0.798 (Copi et al 2007), obtained using the cleaned full sky map of Tegmark, de Oliveira-Costa, & Hamilton (2003) (TOH; henceforth). An alternative statistic that tests the planarity is given by the angular momentum dispersion (de Oliveira-Costa et al (2004)).…”

“…To quantify this lack of correlation, we follow past work (Spergel et al 2003;Copi et al 2007;Copi, Huterer, Schwarz, & Starkman 2009) and adopt the S 1/2 statistic to test the total amount of correlation at angles above 60 • :…”

“…Attempts to explain these anomalies include astrophysical, instrumental, cosmological causes, as well as arguments that faulty data analysis or a posteriori statistics are at work (for a review, see Copi, Huterer, Schwarz, & Starkman (2010)). Two particularly puzzling features at large angular scales are the alignments of large-angle anisotropies (de Oliveira-Costa, Tegmark, Zaldarriaga, & Hamilton 2004;Schwarz, Starkman, Huterer, & Copi 2004;Land & Magueijo 2005;Copi, Huterer, Schwarz, & Starkman 2006), and the low power at large scales (Spergel et al 2003;Copi, Huterer, Schwarz, & Starkman 2007); each of these anomalies are 1% likely. For reviews with differing points of view see Bennett et al (2010); Copi et al (2010).…”