Microwave background correlations from dipole anisotropy modulation

Full-sky maps of the cosmic microwave background temperature reveal a 7% asymmetry of fluctuation power between two halves of the sky. A common phenomenological model for this asymmetry is an overall dipole modulation of statistically isotropic fluctuations, which produces particular off-diagonal co...

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Veröffentlicht in:Physical review. D 2015-09, Vol.92 (6), Article 063008
Hauptverfasser: Aiola, Simone, Wang, Bingjie, Kosowsky, Arthur, Kahniashvili, Tina, Firouzjahi, Hassan
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Sprache:eng
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Zusammenfassung:Full-sky maps of the cosmic microwave background temperature reveal a 7% asymmetry of fluctuation power between two halves of the sky. A common phenomenological model for this asymmetry is an overall dipole modulation of statistically isotropic fluctuations, which produces particular off-diagonal correlations between multipole coefficients. We compute these correlations and construct corresponding estimators for the amplitude and direction of the dipole modulation. Applying these estimators to various cut-sky temperature maps from Planck and WMAP data shows consistency with a dipole modulation, differing from a null signal at 2.5[sigma], with an amplitude and direction consistent with previous fits based on the temperature fluctuation power. The signal is scale dependent, with a statistically significant amplitude at angular scales larger than 2[degrees]. Future measurements of microwave background polarization and gravitational lensing can increase the significance of the signal. If the signal is not a statistical fluke in an isotropic universe, it requires new physics beyond the standard model of cosmology.
ISSN:1550-7998
2470-0010
1550-2368
2470-0029
DOI:10.1103/PhysRevD.92.063008