Signal-to-Noise Eigenmode Analysis of the Two-Year COBE Maps

To test best a theory of cosmic microwave background fluctuations, anisotropy maps [here the two-year Cosmic Background Explorer differential microwave radiometer (DMR) $53,90,31\mathrm{GHz}$ $a$ and $b$ and the Far-Infrared Survey (FIRS) 170 GHz maps] are expanded in a complete basis of linear combinations of pixel amplitudes—statistically independent for both the noise and the signal. Bayesian analysis of a 2-parameter inflation-inspired theory shows the overall band-power and spectral tilt index ${\nu }_{\Delta T}+1\mathrm{}$ for all maps agree within $1\sigma$, $\{(1.1\pm 0.1)\times {10}^{-5\mathrm{}}{\}}^2$ and $1.27\pm 0.33$ (compatible with inflation values, $\sim 0.8-1.2$); and $S/N$ filtering of the DMR maps reveals the same large-scale structural features.