FourYear COBE DMR Cosmic Microwave Background Observations: Maps and Basic Results
Abstract
In this Letter we present a summary of the spatial properties of the cosmic microwave background radiation based on the full 4 yr of COBE Differential Microwave Radiometer (DMR) observations, with additional details in a set of companion Letters. The anisotropy is consistent with a scaleinvariant powerlaw model and Gaussian statistics. With full use of the multifrequency 4 yr DMR data, including our estimate of the effects of Galactic emission, we find a powerlaw spectral index of n = 1.2 +/ 0.3 and a quadrupole normalization QrmsPS = 15.3^{+3.8}_{2.8} mu K. For n = 1 the bestfit normalization is QrmsPSn=1 = 18 +/ 1.6 mu K. These values are consistent with both our previous 1 yr and 2 yr results. The results include use of the l = 2 quadrupole term; exclusion of this term gives consistent results, but with larger uncertainties. The final DMR 4 yr sky maps, presented in this Letter, portray an accurate overall visual impression of the anisotropy since the signaltonoise ratio is ~2 per 10 deg sky map patch. The improved signaltonoise ratio of the 4 yr maps also allows for improvements in Galactic modeling and limits on nonGaussian statistics.
 Publication:

The Astrophysical Journal
 Pub Date:
 June 1996
 DOI:
 10.1086/310075
 arXiv:
 arXiv:astroph/9601067
 Bibcode:
 1996ApJ...464L...1B
 Keywords:

 COSMOLOGY: COSMIC MICROWAVE BACKGROUND;
 COSMOLOGY: OBSERVATIONS;
 Astrophysics
 EPrint:
 11 pages plus 2 PostScript figures. Figures 2 and 4 are not included, but are available upon request to bennett@stars.gsfc.nasa.gov. Submitted to The Astrophysical Journal (Letters)