SEVEN-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP ) OBSERVATIONS: ARE THERE COSMIC MICROWAVE BACKGROUND ANOMALIES?

Journal Article · Tue Feb 01 00:00:00 EST 2011 · Astrophysical Journal, Supplement Series

DOI:https://doi.org/10.1088/0067-0049/192/2/17· OSTI ID:21562759

Bennett, C L; Larson, D; Gold, B ^[1]; Hill, R S; Odegard, N; Weiland, J L ^[2]; Hinshaw, G; Kogut, A; Wollack, E ^[3]; Smith, K M; Spergel, D N ^[4]; Dunkley, J ^[5]; Halpern, M ^[6]; Jarosik, N; Page, L ^[7]; Komatsu, E ^[8]; Limon, M ^[9]; Meyer, S S ^[10]; Nolta, M R ^[11]; Tucker, G S ^[12]

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1. Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218-2686 (United States)
2. ADNET Systems, Inc., 7515 Mission Dr., Suite A100 Lanham, MD 20706 (United States)
3. Code 665, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
4. Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544-1001 (United States)
5. Astrophysics, University of Oxford, Keble Road, Oxford, OX1 3RH (United Kingdom)
6. Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada)
7. Department of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544-0708 (United States)
8. University of Texas, Austin, Department of Astronomy, 2511 Speedway, RLM 15.306, Austin, TX 78712 (United States)
9. Columbia Astrophysics Laboratory, 550 W. 120th St., Mail Code 5247, New York, NY 10027-6902 (United States)
10. Departments of Astrophysics and Physics, KICP and EFI, University of Chicago, Chicago, IL 60637 (United States)
11. Canadian Institute for Theoretical Astrophysics, 60 St. George St, University of Toronto, Toronto, ON M5S 3H8 (Canada)
12. Department of Physics, Brown University, 182 Hope St., Providence, RI 02912-1843 (United States)

A simple six-parameter {Lambda}CDM model provides a successful fit to WMAP data. This holds both when the WMAP data are analyzed alone or in combination with other cosmological data. Even so, it is appropriate to examine the data carefully to search for hints of deviations from the now standard model of cosmology, which includes inflation, dark energy, dark matter, baryons, and neutrinos. The cosmological community has subjected the WMAP data to extensive and varied analyses. While there is widespread agreement as to the overall success of the six-parameter {Lambda}CDM model, various 'anomalies' have been reported relative to that model. In this paper we examine potential anomalies and present analyses and assessments of their significance. In most cases we find that claimed anomalies depend on posterior selection of some aspect or subset of the data. Compared with sky simulations based on the best-fit model, one can select for low probability features of the WMAP data. Low probability features are expected, but it is not usually straightforward to determine whether any particular low probability feature is the result of the a posteriori selection or non-standard cosmology. Hypothesis testing could, of course, always reveal an alternative model that is statistically favored, but there is currently no model that is more compelling. We find that two cold spots in the map are statistically consistent with random cosmic microwave background (CMB) fluctuations. We also find that the amplitude of the quadrupole is well within the expected 95% confidence range and therefore is not anomalously low. We find no significant anomaly with a lack of large angular scale CMB power for the best-fit {Lambda}CDM model. We examine in detail the properties of the power spectrum data with respect to the {Lambda}CDM model and find no significant anomalies. The quadrupole and octupole components of the CMB sky are remarkably aligned, but we find that this is not due to any single map feature; it results from the statistical combination of the full-sky anisotropy fluctuations. It may be due, in part, to chance alignments between the primary and secondary anisotropy, but this only shifts the coincidence from within the last scattering surface to between it and the local matter density distribution. While this alignment appears to be remarkable, there was no model that predicted it, nor has there been a model that provides a compelling retrodiction. We examine claims of a hemispherical or dipole power asymmetry across the sky and find that the evidence for these claims is not statistically significant. We confirm the claim of a strong quadrupolar power asymmetry effect, but there is considerable evidence that the effect is not cosmological. The likely explanation is an insufficient handling of beam asymmetries. We conclude that there is no compelling evidence for deviations from the {Lambda}CDM model, which is generally an acceptable statistical fit to WMAP and other cosmological data.

• OSTI ID: 21562759
• Journal Information: Astrophysical Journal, Supplement Series, Vol. 192, Issue 2; Other Information: DOI: 10.1088/0067-0049/192/2/17; ISSN 0067-0049
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ANISOTROPY
COSMOLOGY
NONLUMINOUS MATTER
RELICT RADIATION
STANDARD MODEL
TELESCOPES
UNIVERSE
ELECTROMAGNETIC RADIATION
FIELD THEORIES
GRAND UNIFIED THEORY
MATHEMATICAL MODELS
MATTER
MICROWAVE RADIATION
PARTICLE MODELS
QUANTUM FIELD THEORY
RADIATIONS
UNIFIED GAUGE MODELS