First-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: The Angular Power Spectrum
Abstract
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)Cl/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 CTEl 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.
WMAP is the result of a partnership between Princeton University and the NASA Goddard Space Flight Center. Scientific guidance is provided by the WMAP Science Team.- Publication:
-
The Astrophysical Journal Supplement Series
- Pub Date:
- September 2003
- DOI:
- 10.1086/377225
- arXiv:
- arXiv:astro-ph/0302217
- Bibcode:
- 2003ApJS..148..135H
- Keywords:
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- Cosmology: Cosmic Microwave Background;
- Cosmology: Cosmological Parameters- Cosmology: Observations;
- Cosmology: Early Universe;
- Cosmology: Large-Scale Structure of Universe;
- Space Vehicles: Instruments;
- Astrophysics
- E-Print:
- One of thirteen companion papers on first-year WMAP results submitted to ApJ