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

Pablo Fosalba, I. Szapudi

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

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 Cl'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 l ≲ 700; the highest l's are still compatible within 1 σ errors. We use a novel intrabin variance method to constrain Cl errors in a model-independent way. Simulations show that our implementation of the technique is unbiased within 1% for l ≲ 100. When applied to WMAP data, the intrabin variance estimator yields diagonal errors ∼10% 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 X2 per degree of freedom (dof) of 1.042 for a best-fit ACDM model, which has a 14% probability, whereas the WMAP team obtained X2/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 ACDM models, we obtain the reionization optical depth τ = 0.145 ± 0.067, spectral index ns = 0.99 ± 0.04, Hubble constant h = 0.67 ± 0.05, baryon density Ωbh2 = 0.0218 ± 0.0014, cold dark matter density ΩCDMh2 = 0.122 ± 0.018, and σ8 = 0.92 ± 0.12, consistent with a reionization redshift zre = 16 ± 5 (68% CL).

Original languageEnglish
JournalAstrophysical Journal
Volume617
Issue number2 II
DOIs
Publication statusPublished - Dec 20 2004

Fingerprint

Microwave Anisotropy Probe
power spectra
anisotropy
probe
estimators
multipoles
degrees of freedom
Hubble constant
Markov chains
optical thickness
cross correlation
Markov chain
microwave
baryons
dark matter
optical depth
simulation
power law
estimates

Keywords

  • Cosmic microwave background
  • Cosmology: theory
  • Methods: statistical

ASJC Scopus subject areas

  • Space and Planetary Science
  • Nuclear and High Energy Physics

Cite this

The angular power spectrum of the first-year Wilkinson Microwave Anisotropy Probe data reanalyzed. / Fosalba, Pablo; Szapudi, I.

In: Astrophysical Journal, Vol. 617, No. 2 II, 20.12.2004.

Research output: Contribution to journalArticle

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abstract = "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 Cl'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 l ≲ 700; the highest l's are still compatible within 1 σ errors. We use a novel intrabin variance method to constrain Cl errors in a model-independent way. Simulations show that our implementation of the technique is unbiased within 1{\%} for l ≲ 100. When applied to WMAP data, the intrabin variance estimator yields diagonal errors ∼10{\%} larger than those reported by the WMAP team for 100 l's and errors, we get a X2 per degree of freedom (dof) of 1.042 for a best-fit ACDM model, which has a 14{\%} probability, whereas the WMAP team obtained X2/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 ACDM models, we obtain the reionization optical depth τ = 0.145 ± 0.067, spectral index ns = 0.99 ± 0.04, Hubble constant h = 0.67 ± 0.05, baryon density Ωbh2 = 0.0218 ± 0.0014, cold dark matter density ΩCDMh2 = 0.122 ± 0.018, and σ8 = 0.92 ± 0.12, consistent with a reionization redshift zre = 16 ± 5 (68{\%} CL).",
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