Power Spectrum of Primordial Inhomogeneity Determined from the 4 - Year COBE 1 DMR Sky Maps

Fourier analysis and power spectrum estimation of the cosmic microwave background anisotropy on an incompletely sampled sky developed by Górski (1994) has been applied to the high-latitude portion of the 4-year COBE DMR 31.5, 53 and 90 GHz sky maps. Likelihood analysis using newly constructed Galaxy cuts (extended beyond |b| = 20 deg to excise the known foreground emission) and simultaneously correcting for the faint high latitude galactic foreground emission is conducted on the DMR sky maps pixelized in both ecliptic and galactic coordinates. The Bayesian power spectrum estimation from the foreground corrected 4-year COBE DMR data renders n ∼ 1.2 ± 0.3, and Q rms−P S ∼ 15.3 +3.7 −2.8 µK (projections of the two-parameter likelihood). These results are consistent with the Harrison-Zel'dovich n = 1 model of amplitude Q rms−P S ∼ 18 µK detected with significance exceeding 14σ (δQ/Q < ∼ 0.07). (A small power spectrum amplitude drop below the published 2-year results is predominantly due to the application of the new, extended Galaxy cuts.) Subject headings: cosmic microwave background — cosmology: observations — methods: analytical, statistical — large scale structure of the universe 1 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. GSFC is also responsible for the analysis software and for the production of the mission data sets.