First-year Wilkinson Microwave Anisotropy Probe (WMAP) observations: The angular power spectrum

G. Hinshaw, D. N. Spergel, L. Verde, R. S. Hill, S. S. Meyer, C. Barnes, C. L. Bennett, M. Halpern, N. Jarosik, A. Kogut, E. Komatsu, M. Limon, L. Page, G. S. Tucker, J. L. Weiland, E. Wollack, E. L. Wright

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We present the angular power spectrum derived from the first-year Wilkinson Microwave Anisotropy Probe (WMAP) sky maps. We study a variety of power spectrum estimation methods and data combinations and demonstrate that the results are robust. The data are modestly contaminated by diffuse Galactic foreground emission, but we show that a simple Galactic template model is sufficient to remove the signal. Point sources produce a modest contamination in the low-frequency data. After masking ∼700 known bright sources from the maps, we estimate that residual sources contribute ∼3500 μK2 at 41 GHz and ∼130 μK2 at 94 GHz to the power spectrum [ℓ(ℓ + 1)C/2π] at ℓ = 1000. Systematic errors are negligible compared to the (modest) level of foreground emission. Our best estimate of the power spectrum is derived from 28 cross-power spectra of statistically independent channels. The final spectrum is essentially independent of the noise properties of an individual radiometer. The resulting spectrum provides a definitive measurement of the cosmic microwave background (CMB) power spectrum, with uncertainties limited by cosmic variance, up to ℓ ∼ 350. The spectrum clearly exhibits a first acoustic peak at l = 220 and a second acoustic peak at ℓ ∼ 540 (Page and coworkers), and it provides strong support for adiabatic initial conditions (Spergel and coworkers). Kogut and coworkers analyze the CTE power spectrum and present evidence for a relatively high optical depth and an early period of cosmic reionization. Among other things, this implies that the temperature power spectrum has been suppressed by ∼30% on degree angular scales, as a result of secondary scattering.

Original languageEnglish (US)
Pages (from-to)135-159
Number of pages25
JournalAstrophysical Journal, Supplement Series
Issue number1
StatePublished - Sep 2003

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Cosmic microwave background
  • Cosmological parameters
  • Cosmology: observations
  • Early universe
  • Large-scale structure of universe
  • Space vehicles: instruments


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