Cosmic Temperature Fluctuations from Two Years of COBE Differential Microwave Radiometers Observations
Abstract
The first two years of COBE DMR observations of the CMB anisotropy are analyzed and compared with our previously published first year results. The results are consistent, but the addition of the second year of data increases the precision and accuracy of the detected CMB temperature fluctuations. The twoyear 53 GHz data are characterized by RMS temperature fluctuations of DT=44+/7 uK at 7 degrees and DT=30.5+/2.7 uK at 10 degrees angular resolution. The 53X90 GHz crosscorrelation amplitude at zero lag is C(0)^{1/2}=36+/5 uK (68%CL) for the unsmoothed 7 degree DMR data. A likelihood analysis of the cross correlation function, including the quadrupole anisotropy, gives a most likely quadrupolenormalized amplitude Q_{rmsPS}=12.4^{+5.2}_{3.3} uK (68% CL) and a spectral index n=1.59^{+0.49}_{0.55} for a power law model of initial density fluctuations, P(k)~k^n. With n fixed to 1.0 the most likely amplitude is 17.4 +/1.5 uK (68% CL). Excluding the quadrupole anisotropy we find Q_{rmsPS}= 16.0^{+7.5}_{5.2} uK (68% CL), n=1.21^{+0.60}_{0.55}, and, with n fixed to 1.0 the most likely amplitude is 18.2+/1.6 uK (68% CL). Monte Carlo simulations indicate that these derived estimates of n may be biased by ~+0.3 (with the observed low value of the quadrupole included in the analysis) and {}~+0.1 (with the quadrupole excluded). Thus the most likely biascorrected estimate of n is between 1.1 and 1.3. Our best estimate of the dipole from the twoyear DMR data is 3.363+/0.024 mK towards Galactic coordinates (l,b)= (264.4+/0.2 degrees, +48.1+/0.4 degrees), and our best estimate of the RMS quadrupole amplitude in our sky is 6+/3 uK.
 Publication:

The Astrophysical Journal
 Pub Date:
 December 1994
 DOI:
 10.1086/174918
 arXiv:
 arXiv:astroph/9401012
 Bibcode:
 1994ApJ...436..423B
 Keywords:

 Background Radiation;
 Cosmology;
 Extraterrestrial Radio Waves;
 Microwaves;
 Radio Astronomy;
 Spaceborne Astronomy;
 Temperature Distribution;
 Universe;
 Anisotropy;
 Computerized Simulation;
 Cosmic Background Explorer Satellite;
 Microwave Radiometers;
 Monte Carlo Method;
 Astronomy;
 COSMOLOGY: COSMIC MICROWAVE BACKGROUND;
 COSMOLOGY: LARGESCALE STRUCTURE OF UNIVERSE;
 COSMOLOGY: OBSERVATIONS;
 Astrophysics
 EPrint:
 Accepted by the Astrophysical Journal. Modifications include the addition of a quadrupole removed correlation function and an analysis of the technique bias on the power spectral index, n. The most likely, debiased, estimate of n is between 1.1 and 1.3. 57 pages of uuencoded postscript (incl 3 b&