We detect anisotropy in the cosmic microwave background (CMB) at degree angular scales and confirm a previous detection reported by Wollack et al. (1993). The root-mean-squared amplitude of the fluctuations is 44-7+13 μK. This may be expressed as the square root of the angular power spectrum in a band of multipoles between leff = 69-22+29. We find δTl = [l(2l + 1)〈|alm|2〉/4π]1/2 = 42-7+12 μK. The measured spectral index of the fluctuations is consistent with zero, the value expected for the CMB. The spectral index corresponding to Galactic free-free emission, the most likely foreground contaminant, is rejected at ∼ 3 σ. The analysis is based on three independent data sets. The first, taken in 1993, spans the 26-36 GHz frequency range with three frequency bands; the second was taken with the same radiometer as the first but during an independent observing campaign in 1994; and the third, also taken in 1994, spans the 36-46 GHz range in three bands. For each telescope position and radiometer channel, the drifts in the instrument offset are ≤4 μK day-1 averaged over a period of 1 month. The dependence of the inferred anisotropy on the calibration and data editing is addressed.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
- Cosmic microwave background
- Cosmology: observations