Cosmic Background Explorer/FIRAS

Product Name
CMB Monopole Spectrum


Fixsen et al. (1996) modeled the full FIRAS low-frequency calibrated sky spectra as a superposition of a CMB monopole, a CMB dipole and selected Galactic emission components. Table 4 of their paper gives the residuals of the derived CMB monopole spectrum from a perfect blackbody. Subsequent analyses by Mather et al. (1999) and Fixsen et al. (2002) improved the FIRAS calibration accuracy and provided a best-estimate for the absolute CMB temperature of 2725 +/- 1 mK.

The CMB monopole spectrum posted here is the sum of a 2.725 K blackbody spectrum and the residual intensity noted above. The complete contents of Table 4 are also provided, in the form of the original residuals, 1-sigma uncertainties, and the modeled Galaxy spectrum.

More details can be found in:

"The Spectral Results of the Far-Infrared Absolute Spectrophotometer Instrument on COBE"
D.J. Fixsen & J.C. Mather, 2002 ApJ 581,817

"Calibrator Design for the COBE Far-Infrared Absolute Spectrophotometer (FIRAS)"
J.C. Mather, et al., 1999 ApJ 512, 511

"The Cosmic Microwave Background Spectrum from the full COBE FIRAS Data Set"
D.J. Fixsen, et al., 1996 ApJ 473, 576

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