First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Angular Power Spectrum

Details First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Angular Power Spectrum First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Angular Power Spectrum

2003-02-11

arxiv.org/abs/astro-ph/0302217v1

Astrophys.J.Suppl.148:135,2003

Astronomy and Astrophysics

Astrophysics

One of thirteen companion papers on first-year WMAP results submitted to ApJ; 44 pages, 14 figures; a version with higher qual

Scientific paper

10.1086/377225

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 residual sources contribute ~3500 uK^2 at 41 GHz, and ~130 uK^2 at 94 GHz, to the power spectrum l*(l+1)*C_l/(2*pi) 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 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 and it provides strong support for adiabatic initial conditions. Kogut et al. (2003) analyze the C_l^TE 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, due to secondary scattering.

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