Astronomy and Astrophysics – Astrophysics
Scientific paper
1997-05-15
Mon.Not.Roy.Astron.Soc. 295 (1998) L35
Astronomy and Astrophysics
Astrophysics
5 pages, 1 figure. Revised to match published version: MNRAS Letters 1998, 295, 35
Scientific paper
10.1046/j.1365-8711.1998.01439.x
We compare the latest results from CMB experiments at scales around $l_e \sim 150$ over different parts of the sky to test the hypothesis that they are drawn from a Gaussian distribution, as is usually assumed. Using both the diagonal and the full covariance $\chi^2$ test, we compare the data with different sets of strategies and find in all cases incompatibility with the Gaussian hypothesis above the one-sigma level. We next show how to include a generic non-Gaussian signal in the data analysis. Results from CMB observations can be made compatible with each other by assuming a non-Gaussian distribution for the signal, with a kurtosis at a level $B_4 = <{\delta_T^4}>_c /{<{\delta_T^2}>_c}^2 \simeq 90$. A possible interpretation for this result is that the initial fluctuations at the surface of last scattering are strongly non-Gaussian. Another interpretation is that the systematic errors have been understimated in all observations by a factor of two. Other explanations include foreground contamination, non-linear effects or a combination of them.
Elizalde Emilio
Fosalba Pablo
Gaztanaga Enrique
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