Abstract
We cross correlate the new 3 year Wilkinson Microwave Anistropy Probe (WMAP) cosmic microwave background data with the NRAO VLA Sky Survey radio galaxy data and find further evidence of late integrated Sachs-Wolfe (ISW) effect taking place at late times in cosmic history. Our detection makes use of a novel statistical method (P. Baldi, G. Kerkyacharian, D. Marinucci, and D. Picard, math.ST/0606154 and P. Baldi, G. Kerkyacharian, D. Marinucci, D. Picard, math.ST/0606599) based on a new construction of spherical wavelets, called needlets. The null hypothesis (no ISW) is excluded at more than 99.7% confidence. When we compare the measured cross correlation with the theoretical predictions of standard, flat cosmological models with a generalized dark energy component parameterized by its density, , equation of state and speed of sound , we find at 95% C.L., independently of and . If dark energy is assumed to be a cosmological constant (), the bound on density shrinks to . Models without dark energy are excluded at more than . The bounds on depend rather strongly on the assumed value of . We find that models with more negative equation of state (such as phantom models) are a worse fit to the data in the case than in the case .
- Received 20 June 2006
DOI:https://doi.org/10.1103/PhysRevD.74.043524
©2006 American Physical Society