The Astrophysical Journal Letters

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The Astrophysical Journal Letters Volume 464 Number 1 Create an alert RSS this journal

C. L. Bennett et al 1996 ApJ 464 L1 doi:10.1086/310075

Four-Year COBE* DMR Cosmic Microwave Background Observations: Maps and Basic Results

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C. L. Bennett1, A. J. Banday2, K. M. Górski2, G. Hinshaw2, P. Jackson2, P. Keegstra2, A. Kogut2, G. F. Smoot3, D. T. Wilkinson4 and E. L. Wright5

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Abstract References Cited By

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 scale-invariant power-law 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 power-law spectral index of n = 1.2 ± 0.3 and a quadrupole normalization Qrms-PS = 15.3−2.8+3.8 μK. For n = 1 the best-fit normalization is Qrms-PS|n=1 = 18 ± 1.6 μK. These values are consistent with both our previous 1 yr and 2 yr results. The results include use of the ell = 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 signal-to-noise ratio is ~2 per 10° sky map patch. The improved signal-to-noise ratio of the 4 yr maps also allows for improvements in Galactic modeling and limits on non-Gaussian statistics.


Footnote
*  NASA/GSFC is responsible for the design, development, and operations of the COBE, and for the development of the analysis software and the delivery of the mission data sets. Scientific guidance is provided by the COBE Science Working Group.
Subject headings

cosmic microwave background; cosmology: observations


Dates

Issue 1 (1996 June 10)

Received 1996 January 11, accepted for publication 1996 March 21



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