First‐YearWilkinson Microwave Anisotropy Probe(WMAP) Observations: Interpretation of the TT and TE Angular Power Spectrum Peaks

Publisher Website
Google Scholar
Abstract
The CMB has distinct peaks in both its temperature angular power spectrum (TT) and temperature-polarization cross-power spectrum (TE). From the WMAP data we find the first peak in the temperature spectrum at ℓ = 220.1 ± 0.8 with an amplitude of 74.7 ± 0.5 μK; the first trough at ℓ = 411.7 ± 3.5 with an amplitude of 41.0 ± 0.5 μK; and the second peak at ℓ = 546 ± 10 with an amplitude of 48.8 ± 0.9 μK. The TE spectrum has an antipeak at ℓ = 137 ± 9 with a cross-power of -35 ± 9 μK2, and a peak at ℓ = 329 ± 19 with cross-power 105 ± 18 μK2. All uncertainties are 1 σ and include calibration and beam errors. An intuition for how the data determine the cosmological parameters may be gained by limiting one's attention to a subset of parameters and their effects on the peak characteristics. We interpret the peaks in the context of a flat adiabatic ΛCDM model with the goal of showing how the cosmic baryon density, Ωbh2, matter density, Ωmh2, scalar index, ns, and age of the universe are encoded in their positions and amplitudes. To this end, we introduce a new scaling relation for the TE antipeak-to-peak amplitude ratio and recompute known related scaling relations for the TT spectrum in light of the WMAP data. From the scaling relations, we show that WMAP's tight bound on Ωbh2 is intimately linked to its robust detection of the first and second peaks of the TT spectrum.