The angular power spectrum of the first-year Wilkinson Microwave Anisotropy Probe data reanalyzed

We measure the angular power spectrum of the Wilkinson Microwave Anisotropy Probe (WMAP) first-year temperature anisotropy maps. We use the Spatially Inhomogeneous Correlation Estimator (SpICE) to estimate C-l's for multipoles l=2-900 from all possible cross-correlation channels. Except for the map-making stage, our measurements provide an independent analysis of that by G. Hinshaw et al. Despite the different methods used, there is virtually no difference between the two measurements for lless than or similar to700; the highest l's are still compatible within 1 sigma errors. We use a novel intrabin variance method to constrain C-l errors in a model-independent way. Simulations show that our implementation of the technique is unbiased within 1% for lgreater than or similar to100. When applied to WMAP data, the intrabin variance estimator yields diagonal errors similar to10% larger than those reported by the WMAP team for 100<l<450. This translates into a 2.4 sigma detection of systematics, since no difference is expected between the SpICE and the WMAP team estimator window functions in this multipole range. With our measurement of the C-l's and errors, we get a chi(2) per degree of freedom (dof) of 1.042 for a best-fit LambdaCDM model, which has a 14% probability, whereas the WMAP team obtained chi(2)/dof=1.066, which has a 5% probability. We assess the impact of our results on cosmological parameters using Markov chain Monte Carlo simulations. From WMAP data alone, assuming spatially flat power-law LambdaCDM models, we obtain the reionization optical depth tau=0.145+/-0.067, spectral index n(s)=0.99+/-0.04, Hubble constant h=0.67+/-0.05, baryon density Omega(b)h(2)=0.0218+/-0.0014, cold dark matter density Omega(CDM)h(2)=0.122+/-0.018, and sigma(8)=0.92+/-0.12, consistent with a reionization redshift z(re)=16+/-5(68% CL).