FIVE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE OBSERVATIONS: DATA PROCESSING, SKY MAPS, AND BASIC RESULTS

Abstract

We present new full-sky temperature and polarization maps in five frequency bands from 23 to 94 GHz, based on data from the first five years of the Wilkinson Microwave Anisotropy Probe (WMAP) sky survey. The new maps are consistent with previous maps and are more sensitive. The five-year maps incorporate several improvements in data processing made possible by the additional years of data and by a more complete analysis of the instrument calibration and in-flight beam response. We present several new tests for systematic errors in the polarization data and conclude that W-band polarization data is not yet suitable for cosmological studies, but we suggest directions for further study. We do find that Ka-band data is suitable for use; in conjunction with the additional years of data, the addition of Ka band to the previously used Q- and V-band channels significantly reduces the uncertainty in the optical depth parameter, τ. Further scientific results from the five-year data analysis are presented in six companion papers and are summarized in Section 7 of this paper. With the five-year WMAP data, we detect no convincing deviations from the minimal six-parameter ΛCDM model: a flat universe dominated by a cosmological constant, with adiabatic and nearly scale-invariant Gaussian fluctuations. Using WMAP data combined with measurements of Type Ia supernovae and Baryon Acoustic Oscillations in the galaxy distribution, we find (68% CL uncertainties): Ω _b h ² = 0.02267^+0.00058 _–0.00059, Ω _c h ² = 0.1131 ± 0.0034, Ω_Λ = 0.726 ± 0.015, n_s = 0.960 ± 0.013, τ = 0.084 ± 0.016, and at k = 0.002 Mpc^-1. From these we derive σ₈ = 0.812 ± 0.026, H ₀ = 70.5 ± 1.3 km s^-1 Mpc^–1, Ω _b = 0.0456 ± 0.0015, Ω _c = 0.228 ± 0.013, Ω _m h ² = 0.1358^+0.0037 _–0.0036, z _reion = 10.9 ± 1.4, and t ₀ = 13.72 ± 0.12 Gyr. The new limit on the tensor-to-scalar ratio is r < 0.22(95%CL), while the evidence for a running spectral index is insignificant, dn_s /dln k = –0.028 ± 0.020 (68% CL). We obtain tight, simultaneous limits on the (constant) dark energy equation of state and the spatial curvature of the universe: –0.14 < 1 + w < 0.12(95%CL) and –0.0179 < Ω _k < 0.0081(95%CL). The number of relativistic degrees of freedom, expressed in units of the effective number of neutrino species, is found to be N _eff = 4.4 ± 1.5 (68% CL), consistent with the standard value of 3.04. Models with N _eff = 0 are disfavored at >99.5% confidence. Finally, new limits on physically motivated primordial non-Gaussianity parameters are –9 < f ^local _NL < 111 (95% CL) and –151 < f ^equil _NL < 253 (95% CL) for the local and equilateral models, respectively.