A degree scale anisotropy measurement of the cosmic microwave background near the star gamma ursae minoris

J. O. Gundersen, A. C. Clapp, M. Devlin, W. Holmes, M. L. Fischer, P. R. Meinhold, A. E. Lange, P. M. Lubin, P. L. Richards, G. F. Smoot

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66 Scopus citations


Results from a search for anisotropy in the cosmic microwave background (CMB) are presented from the third flight of the Millimeter-wave Anisotropy eXperiment. Observations were made at 6, 9, and 12 cm-1 with a 0.°5 FWHM beam and a 1.°3 sinusoidal chop. The CMB observation occurred over 1.37 hours and covered a 6.24 deg2 area of the sky where very little foreground emission is expected. Significant correlated structure is observed at 6 and 9 cm-1. At 12 cm-1 we place an upper limit on the structure. The relative amplitudes at 6, 9, and 12 cm-1 are consistent with a CMB spectrum. The spectrum of the structure is inconsistent with thermal emission from known forms of interstellar dust. Synchrotron and free-free emission would both require unusually flat spectral indices at cm wavelengths in order to account for the amplitude of the observed structure. Although known systematic errors are not expected to contribute significantly to any of the three optical channels, excess sidelobe contamination cannot be definitively ruled out. If all the structure is attributed to CMB anisotropy, a value of the weighted rms of the 6 and 9 cm-1 channels of ΔTrms/TCMB = 4.7 ± 0.8 × 10-5 (±1 σ) was measured. If the CMB anisotropy is assumed to have a Gaussian autocorrelation function with a coherence angle of 25', then the most probable value is ΔT/TCMB = 4.2-1.1+1.7 × 10-5, where the ± refers to the 95% confidence limits. These values are similar to a measurement made in the same region of the sky on a previous flight; however, this lower limit is larger than the upper limit that was obtained in a different region of the sky during the same flight.

Original languageEnglish (US)
Pages (from-to)L1-L5
JournalAstrophysical Journal
Issue number1 PART 2
StatePublished - Aug 10 1993
Externally publishedYes


  • Cosmic microwave background
  • Cosmology: observations

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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