Testing for non-Gaussianity in the WMAP data: Minkowski functionals and the length of the skeleton

Preprint
Publisher Website
Google Scholar
  • 14 January 2004
Abstract
The three Minkowski functionals and the recently defined length of the skeleton are estimated for the co-added first-year WMAP data, and compared with 5000 Monte Carlo simulations, based on Gaussian fluctuations with the a-priori best-fit running-index power spectrum and WMAP-like beam and noise properties. A number of power spectrum dependent quantities, such as the number of stationary points, the total length of the skeleton, and a spectral parameter, gamma, are also estimated. While the area and length Minkowski functionals and the length of the skeleton show no evidence for departures from the Gaussian hypothesis, the northern hemisphere genus has a chi^2 that is large at the 95% level on all scales. For a smoothing scale of 8 degrees FWHM it is larger than that found in 99.5% of the simulations. Also, the WMAP genus for negative thresholds in the northern hemisphere has an amplitude that is larger than in the simulations with a significance of more than 3 sigma. On scales smaller than 2 degrees, the number of extrema in the WMAP data is high at the 3 sigma level. However, this last result can probably be attributed to the effect of point sources. Also, the spectral parameter gamma is high at the 99% level in the northern galactic hemisphere, while perfectly acceptable in the southern hemisphere, consistent with the previously reported power asymmetry between the two regions.

This publication has 0 references indexed in Scilit: