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Week of August 29, 2010

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"Five-year Wilkinson Microwave Anistropy Probe observations: Likelihood and parameters from the WMAP data," by J. Dunkley and 18 others, Astrophysical Journal Supplement Series, 180(2): 306-29, February 2009.

[Authors' affiliations: 14 U.S., Canadian, and British institutions]

Abstract: "This paper focuses on cosmological constraints derived from analysis of WMAP data alone. A simple Lambda CDM cosmological model fits the five-year WMAP temperature and polarization data. The basic parameters of the model are consistent with the three-year data and now better constrained: Omega(b)h(2) = 0.02273 +/- 0.00062, Omega(c)h(2) = 0.1099 +/- 0.0062, Omega(Lambda) = 0.742 +/- 0.030, n(s) = 0.963(-0.015)(+0.014), tau = 0.087 +/- 0.017, and sigma(8) = 0.796 +/- 0.036, with h = 0.719(-0.027)(+0.026). With five years of polarization data, we have measured the optical depth to reionization, tau > 0, at 5 sigma significance. The redshift of an instantaneous reionization is constrained to be z(reion) = 11.0 +/- 1.4 with 68% confidence. The 2 sigma lower limit is zreion > 8.2, and the 3 sigma limit is z(reion) > 6.7. This excludes a sudden reionization of the universe at z = 6 at more than 3.5 sigma significance, suggesting that reionization was an extended process. Using two methods for polarized foreground cleaning we get consistent estimates for the optical depth, indicating an error due to the foreground treatment of tau similar to 0.01. This cosmological model also fits small-scale cosmic microwave background (CMB) data, and a range of astronomical data measuring the expansion rate and clustering of matter in the universe. We find evidence for the first time in the CMB power spectrum for a nonzero cosmic neutrino background, or a background of relativistic species, with the standard three light neutrino species preferred over the best-fit Lambda CDM model with N-eff = 0 at > 99.5% confidence, and N-eff > 2.3 (95% confidence limit (CL)) when varied. The five-year WMAP data improve the upper limit on the tensor-to-scalar ratio, r < 0.43 (95% CL), for power-law models, and halve the limit on r for models with a running index, r < 0.58 (95% CL). With longer integration we find no evidence for a running spectral index, with dn(s)/d ln k = -0.037 +/- 0.028, and find improved limits on isocurvature fluctuations. The current WMAP-only limit on the sum of the neutrino masses is Sigma m(v) < 1.3 eV (95% CL), which is robust, to within 10%, to a varying tensor amplitude, running spectral index, or dark energy equation of state."

This 2009 report from Astrophysical Journal Supplement Series was cited 66 times in current journal articles indexed by Clarivate Analytics during March/April 2010. With that latest two-month count, this report now stands as the third-most-cited physics paper published in the last two years, excluding reviews. (The #1 spot in physics, incidentally, is currently filled by another report on the Wilkinson Probe, from the same journal issue.) Prior to the most recent bimonthly tally, citations to the paper have accrued as follows:

January-February 2010: 45 citations
November-December 2009: 55
September-October 2009: 75
July-August 2009: 51
May-June 2009: 54
March-April 2009: 19
January-February 2009: 4

Total Citations to date: 369

SOURCE: Hot Papers Database (Included with a subscription to the print newsletter Science Watch®, available from the Research Services Group of Thomson Reuters. Packaged on a CD that is mailed with each Science Watch issue, the Hot Papers Database contains data on hundreds of highly cited papers published during the last two years. User interface permits searching by author, organization, journal, field, and more. Total citations, as well as citations accrued during successive bimonthly periods, can be assessed and graphed. An updated CD containing the most recent bimonthly data is mailed with every new issue of Science Watch, six times a year. The CD also includes an electronic version of the Science Watch issue in HTML format, for personal desktop access.


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