Evidence of Vorticity and Shear at Large Angular Scales in the WMAP Data: A Violation of Cosmological Isotropy?
Motivated by the large-scale asymmetry observed in the cosmic microwave background sky, we consider a specific class of anisotropic cosmological models--Bianchi type VII sub(h)--and compare them to the WMAP first-year data on large angular scales. Remarkably, we find evidence of a correlation that i...
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| Published in: | The Astrophysical journal 2005-08, Vol.629 (1), p.L1-L4 |
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| Main Authors: | , , , , |
| Format: | Article |
| Language: | eng |
| Online Access: | Get full text |
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| Summary: | Motivated by the large-scale asymmetry observed in the cosmic microwave background sky, we consider a specific class of anisotropic cosmological models--Bianchi type VII sub(h)--and compare them to the WMAP first-year data on large angular scales. Remarkably, we find evidence of a correlation that is ruled out as a chance alignment at the 3 s level. The best-fit Bianchi model corresponds to x = 0.55, sub(0) = 0.5, a rotation axis in the direction (l, b) = (222, -62), shear (s/H) sub(0) = 2.4 x 10 super(-10), and a right-handed vorticity (w/H) sub(0) = 4.3 x 10 super(-10). Correcting for this component greatly reduces the significance of the large-scale power asymmetry, resolves several anomalies detected on large angular scales (i.e., the low quadrupole amplitude and quadrupole/octopole planarity and alignment), and can account for a non-Gaussian "cold spot" on the sky. Despite the apparent inconsistency with the best-fit parameters required in inflationary models to account for the acoustic peaks, we consider the results sufficiently provocative to merit further consideration. |
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| ISSN: | 1538-4357 0004-637X 1538-4357 |