Non-Gaussian Statistics at Large Angular Scales: {\it COBE} DMR 2-Year Sky Maps

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Session 57 -- COBE and Related Papers
Display presentation, Tuesday, 10, 1995, 9:20am - 6:30pm

[57.02] Non-Gaussian Statistics at Large Angular Scales: {\it COBE} DMR 2-Year Sky Maps

C.L. Bennett (NASA/GSFC), A. Kogut, G. Hinshaw (HSTX), A.J. Banday (USRA), P.M. Lubin (UCSB), G.F. Smoot (UCB)

The angular distribution of the cosmic microwave background (CMB) probes the distribution of mass and energy in the early universe and provides a means to test competing models of structure formation. One such test is whether or not the distribution of CMB anisotropies follows Gaussian statistics. Attempts to differentiate Gaussian from non-Gaussian distributions on large angular scales are complicated by the tendency of any distribution to approach Gaussian when averaged over a sufficiently large area (the central limit theorem) and by our inability to measure more than one sample (our observable universe) of the theoretical parent distribution (``cosmic variance''). We use the two-point correlation function of the extrema points (peaks and valleys) in the COBE Differential Microwave Radiometers (DMR) 2-year sky maps as a test for non-Gaussian temperature distribution in the cosmic microwave background anisotropy. A maximum likelihood analysis compares the DMR data to $n=1$ toy models whose random-phase spherical harmonic components $a_{\ell m}$ are drawn from either Gaussian, $\chi^2$, or log-normal parent populations. The likelihood of the 53 GHz (A+B)/2 data is greatest for the exact Gaussian model. All non-Gaussian models tested are ruled out at 90\% confidence, limited by type II errors in the statistical inference. The extrema correlation function is a stronger test for this class of non-Gaussian models than topological statistics such as the genus.

The National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC) is responsible for the design, development, and operation of the Cosmic Background Explorer (COBE ). Scientific guidance is provided by the COBE Science Working Group.

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