The spectrum of the cosmic microwave background anisotropy from the combined COBE FIRAS and WMAP observations

The cosmic microwave background (CMB) anisotropy data from the COBE Far Infrared Absolute Spectrophotometer (FIRAS) is reanalyzed in light of the Wilkinson Microwave Anisotropy Probe (WMAP) observations. The frequency spectrum of the FIRAS signal that has the spatial distribution seen by WMAP is shown to be consistent with CMB temperature fluctuations well into the Wien region of the spectrum. The consistency of these data, from very different instruments with very different observing strategies, provides compelling support for the interpretation that the signal seen by WMAP is temperature anisotropy of cosmological origin. The data also limit rms fluctuations in the Compton y parameter, observable via the Sunyaev-Zeldovich effect, to Deltay < 3 x 10(-6) (95% confidence level) on similar to 5 degrees angular scales.