1999/04/30 by Benjamin C. Bromley, Max Tegmark · 3 citations
Physics and Astronomy · #Advanced Mathematical Theories and Applications #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1086/312304
published as Astrophys.J.524:L79-L82,2000 · Revised to match accepted ApJL version. 4 pages with 2 figs included. Links and color fig at http://www.sns.ias.edu/~max/gaussianity_frames.html or from [email protected]
arxiv created 1999/08/08 · openalex publication_date 1999/10/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
Two recent papers have claimed detection of non-Gaussian features in the COBE Differential Microwave Radiometer sky maps of the cosmic microwave background. We confirm these results, but argue that Gaussianity is still not convincingly ruled out. Since a score of non-Gaussianity tests have now been published, one might expect some mildly significant results even by chance. Moreover, in the case of one measure that yields a detection, a bispectrum statistic, we find that if the non-Gaussian feature is real, it may well be due to detector noise rather than a non-Gaussian sky signal, since a signal-to-noise analysis localizes it to angular scales smaller than the beam. We study its spatial origin in case it is nonetheless due to a sky signal (e.g., a cosmic string wake or flat-spectrum foreground contaminant). It appears highly localized in the direction b = 39 5, l = 257°, since removing a mere five pixels inside a single COBE beam area centered there makes the effect statistically insignificant. We also test Gaussianity with an eigenmode analysis which allows a sky map to be treated as a random number generator. A battery of tests of this generator yields results consistent with Gaussianity.