Power spectrum of primordial inhomogeneity determined from the four-year COBE DMR sky maps

Fourier analysis and power spectrum estimation of the cosmic microwave background anisotropy on an incompletely sampled sky developed by Gorski has been applied to the 4 yr COBE DMR 31.5, 53, and 90 GHz sky maps. Likelihood analysis using newly constructed Galaxy cuts (extended beyond \b\ = 20 degrees 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 yr COBE DMR data renders n similar to 1.2 +/- 0.3 and Q(rms-PS) similar to 15.3(-2.8)(+3.7) mu K (projections of the two-parameter likelihood). The results are consistent with the Harrison-Zeldovich n =1 model of amplitude Q(rms-PS) similar to 18 mu K detected with significance exceeding 14 sigma (delta Q/Q less than or similar to 0.07). (A small power spectrum amplitude drop below the published 2 yr results is predominantly due to the application of the new, extended Galaxy cuts.)