Details

Autor(en) / Beteiligte

• Larson, D
• Dunkley, J
• Hinshaw, G
• Komatsu, E
• Nolta, M. R
• Bennett, C. L
• Gold, B
• Halpern, M
• Hill, R. S
• Jarosik, N
• Kogut, A
• Limon, M
• Meyer, S. S
• Odegard, N
• Page, L
• Smith, K. M
• Spergel, D. N
• Tucker, G. S
• Weiland, J. L
• Wollack, E
• Wright, E. L

Titel

Seven-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Power Spectra and WMAP-derived Parameters

Ist Teil von

• The Astrophysical journal. Supplement series, 2011-02, Vol.192 (2), p.16-jQuery1323920300301='48'

Ort / Verlag

United States: IOP Publishing

Erscheinungsjahr

2011

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• The WMAP mission has produced sky maps from seven years of observations at L2. We present the angular power spectra derived from the seven-year maps and discuss the cosmological conclusions that can be inferred from WMAP data alone. With the seven-year data, the temperature (TT) spectrum measurement has a signal-to-noise ratio per multipole that exceeds unity for l < 919; and in band powers of width Delta *Dl = 10, the signal-to-noise ratio exceeds unity up to l = 1060. The third acoustic peak in the TT spectrum is now well measured by WMAP. In the context of a flat Delta *LCDM model, this improvement allows us to place tighter constraints on the matter density from WMAP data alone, Delta *W m h 2 = 0.1334+0.0056 --0.0055, and on the epoch of matter-radiation equality, z eq = 3196+134 --133. The temperature-polarization (TE) spectrum is detected in the seven-year data with a significance of 20 Delta *s, compared to 13 Delta *s with the five-year data. We now detect the second dip in the TE spectrum near l ~ 450 with high confidence. The TB and EB spectra remain consistent with zero, thus demonstrating low systematic errors and foreground residuals in the data. The low-l EE spectrum, a measure of the optical depth due to reionization, is detected at 5.5 Delta *s significance when averaged over l = 2-7: l(l + 1)C EE l /(2 Delta *p) = 0.074+0.034 --0.025 Delta *mK2 (68% CL). We now detect the high-l, 24 <= l <= 800, EE spectrum at over 8 Delta *s. The BB spectrum, an important probe of gravitational waves from inflation, remains consistent with zero; when averaged over l = 2-7, l(l + 1)C BB l /(2 Delta *p) < 0.055 Delta *mK2 (95% CL). The upper limit on tensor modes from polarization data alone is a factor of two lower with the seven-year data than it was using the five-year data. The data remain consistent with the simple Delta *LCDM model: the best-fit TT spectrum has an effective Delta *y2 of 1227 for 1170 degrees of freedom, with a probability to exceed of 9.6%. The allowable volume in the six-dimensional space of Delta *LCDM parameters has been reduced by a factor of 1.5 relative to the five-year volume, while the Delta *LCDM model that allows for tensor modes and a running scalar spectral index has a factor of three lower volume when fit to the seven-year data. We test the parameter recovery process for bias and find that the scalar spectral index, ns , is biased high, but only by 0.09 Delta *s, while the remaining parameters are biased by <0.15 Delta *s. The improvement in the third peak measurement leads to tighter lower limits from WMAP on the number of relativistic degrees of freedom (e.g., neutrinos) in the early universe: N eff>2.7(95%CL). Also, using WMAP data alone, the primordial helium mass fraction is found to be Y He = 0.28+0.14 --0.15, and with data from higher-resolution cosmic microwave background experiments included, we now establish the existence of pre-stellar helium at >3 Delta *s. These new WMAP measurements provide important tests of big bang cosmology.