Comments on the Statistical Analysis of Excess Variance in the COBE Differential Microwave Radiometer Maps
Abstract
Cosmic anisotropy produces an excess variance σ_sky_^2^ in the {DELTA}T maps produced by the Differential Microwave Radiometer (DMR) on CO8E that is over and above the instrument noise. After smoothing to an effective resolution of 10^deg^, this excess, σ_sky_(10^deg^), provides an estimate for the amplitude of the primordial density perturbation power spectrum with a cosmic uncertainty of only 12%. We employ detailed Monte Carlo techniques to express the amplitude derived from this statistic in terms of the universal rms quadrupole amplitude, <Q_RMS_^2^>^0.5^. The effects of monopole and dipole subtraction and the nonGaussian shape of the DMR beam cause the derived <Q_RMS_^2^>^0.5^ to be 5%10% larger than would be derived using simplified analytic approximations. We also investigate the properties of two other map statistics: the actual quadrupole and the BoughnCottingham statistic. Both the σ_sky_(10^deg^) statistic and the BoughnCottingham statistic are consistent with the <Q_RMS_^2^>^0.5^ = 17 +/ 5 microK reported by Smoot et al. (1992) and Wright et al. (1992).
 Publication:

The Astrophysical Journal
 Pub Date:
 January 1994
 DOI:
 10.1086/173537
 Bibcode:
 1994ApJ...420....1W
 Keywords:

 Microwave Radiometers;
 Monte Carlo Method;
 Signal To Noise Ratios;
 Sky Surveys (Astronomy);
 Variance (Statistics);
 Anisotropy;
 Cosmic Background Explorer Satellite;
 Cosmology;
 Data Smoothing;
 Power Spectra;
 Quadrupoles;
 Astrophysics;
 COSMOLOGY: COSMIC MICROWAVE BACKGROUND;
 COSMOLOGY: OBSERVATIONS