Significance of the largest scale CMB fluctuations in WMAP

By A. D. Oliveira-Costa, Max Tegmark, M. Zaldarriaga, A. Hamilton. 2003

495 citations recorded by the source corpus.

We investigate anomalies reported in the Cosmic Microwave Background maps from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite on very large angular scales and discuss possible interpretations. Three independent anomalies involve the quadrupole and octopole: 1. The cosmic quadrupole on its own is anomalous at the 1-in-20 level by being low (the cut-sky quadrupole measured by the WMAP team is more strikingly low, apparently due to a coincidence in the orientation of our Galaxy of no cosmological significance); 2. The cosmic octopole on its own is anomalous at the 1-in-20 level by being very planar; 3. The alignment between the quadrupole and octopole is anomalous at the 1-in-60 level. Although the a priori chance of all three occurring is 1 in 24000, the multitude of alternative anomalies one could have looked for dilutes the significance of such a posteriori statistics. The simplest small universe model where the universe has toroidal topology with one small dimension of order half the horizon scale, in the direction towards Virgo, could explain the three items above. However, we rule this model out using two topological tests: the S-statistic and the matched circle test.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/db91bbdd11b83bf4aff94b15270dc47dd73c1ac6

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Citations in the corpus

The non‐Gaussian cold spot in Wilkinson Microwave Anisotropy Probe: significance, morphology and foreground contribution (2006, background): “In the last years some works seem to support the existence of spinning dust emission at frequencies around 10–20 GHz (de Oliveira-Costa et al. 2004b, Watson et al. 2005).”
Power Spectrum Estimation from High-Resolution Maps by Gibbs Sampling (2004, background): “This quadrupole appears to be small compared to the best-ﬁt cosmological model (Spergel et al. 2003; Efstathiou 2003a; de Oliveira-Costa et al. 2004), and several authors have considered what this may imply in terms of new physics.”
POWER ASYMMETRY IN WMAP AND PLANCK TEMPERATURE SKY MAPS AS MEASURED BY A LOCAL VARIANCE ESTIMATOR (2014, background): “…found various anomalous features in the data that hinted at possible violations of the statistical isotropy (see, e.g., Tegmark et al. 2003; de Oliveira-Costa et al. 2004; Vielva et al. 2004; Larson & Wandelt 2004; Land & Magueijo 2005a, 2005b, 2007; McEwen et al. 2005, 2006; Jaffe et al.…”
The Axis of Evil revisited (2006, methodology): “In this paper we focus on anomalies in the largest scale modes, after it was first noted that the quadrupole (ℓ = 2) and octopole (ℓ = 3) appeared to be correlated (de Oliveira-Costa et al. 2004), and their power is suspiciously low.”
On Foreground Removal from the Wilkinson Microwave Anisotropy Probe Data by an Internal Linear Combination Method: Limitations and Implications (2004, methodology): “Here we briefly define the various statistics and refer the interested reader to de Oliveira-Costa et al. (2004) for details on how each quantity actually is computed.”
Cosmology and Fundamental Physics with the Euclid Satellite (2012, methodology): “1, these anomalies include an alignment between the harmonic quadrupole and octupole modes in the temperature anisotropies [388], an asymmetric distribution of CMB power between two hemispheres, or dipole asymmetry [465], the lack of power of the temperature two-point correlation function on large a”
INCREASING EVIDENCE FOR HEMISPHERICAL POWER ASYMMETRY IN THE FIVE-YEAR WMAP DATA (2009, background): “Some early notable examples include unexpected low-ℓ correlations (de Oliveira-Costa et al. 2004), a peculiar large cold spot in the southern Galactic hemisphere (Vielva et al. 2004), and a dipolar distribution of large-scale power (Eriksen et al. 2004a).”
Testing the cosmological principle of isotropy: Local power spectrum estimates of the WMAP data (2004, background): “…multipole range was similar to the morphology seen in the integrated foreground template contribution, suggesting that the low order multipoles may remain compromised by residual Galactic emission (this was also noted by (de Oliveira-Costa et al. 2004; Eriksen et al. 2004c; Schwarz et al. 2004)).”
No large-angle correlations on the non-Galactic microwave sky (2008, methodology): “If the WMAP ILC is a reliable reconstruction of the full-sky CMB, then there is overwhelming evidence (de Oliveira-Costa et al. 2004; Eriksen et al. 2004; Copi, Huterer & Starkman 2004; Schwarz et al. 2004; Copi et al. 2006; Copi et al. 2007; Land & Magueijo 2005a,b,c,d; Rakić & Schwarz 2007; for…”
Probing the anisotropic local Universe and beyond with SNe Ia data (2010, background): “…of anomalies in large-angle anisotropies in the CMB, e.g. the hemispherical asymmetry (Eriksen et al. 2004) and the unexpected quadrupole–octupole alignment (de Oliveira-Costa et al. 2004), have led many to question whether the CMB is indeed statistically isotropic (e.g. Copi et al. 2007).”