Evidence of Vorticity and Shear at Large Angular Scales in the WMAP Data: A Violation of Cosmological Isotropy?
Abstract
Motivated by the largescale asymmetry observed in the cosmic microwave background sky, we consider a specific class of anisotropic cosmological modelsBianchi type VII_{h}and compare them to the WMAP firstyear data on large angular scales. Remarkably, we find evidence of a correlation that is ruled out as a chance alignment at the 3 σ level. The bestfit Bianchi model corresponds to x=0.55, Ω_{0}=0.5, a rotation axis in the direction (l, b) = (222°, 62°), shear (σ/H)_{0}=2.4×10^{10}, and a righthanded vorticity (ω/H)_{0}=4.3×10^{10}. Correcting for this component greatly reduces the significance of the largescale 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 nonGaussian ``cold spot'' on the sky. Despite the apparent inconsistency with the bestfit parameters required in inflationary models to account for the acoustic peaks, we consider the results sufficiently provocative to merit further consideration.
 Publication:

The Astrophysical Journal
 Pub Date:
 August 2005
 DOI:
 10.1086/444454
 arXiv:
 arXiv:astroph/0503213
 Bibcode:
 2005ApJ...629L...1J
 Keywords:

 Cosmology: Cosmic Microwave Background;
 Cosmology: Observations;
 Methods: Numerical;
 Astrophysics
 EPrint:
 4 pages, 3 figures