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Title:
The Cosmological Baryon Density from the Deuterium-to-Hydrogen Ratio in QSO Absorption Systems: D/H toward Q1243+3047
Authors:
Kirkman, David; Tytler, David; Suzuki, Nao; O'Meara, John M.; Lubin, Dan
Affiliation:
AA(), AB(Visiting Astronomer, W. M. Keck Observatory, which is a joint facility of the University of California, the California Institute of Technology, and NASA.; Center for Astrophysics and Space Sciences, University of California at San Diego, MS 0424, La Jolla, CA 92093-0424 .), AC(Visiting Astronomer, W. M. Keck Observatory, which is a joint facility of the University of California, the California Institute of Technology, and NASA.; Center for Astrophysics and Space Sciences, University of California at San Diego, MS 0424, La Jolla, CA 92093-0424 .), AD(Visiting Astronomer, W. M. Keck Observatory, which is a joint facility of the University of California, the California Institute of Technology, and NASA.; Center for Astrophysics and Space Sciences, University of California at San Diego, MS 0424, La Jolla, CA 92093-0424 .), AE(Visiting Astronomer, W. M. Keck Observatory, which is a joint facility of the University of California, the California Institute of Technology, and NASA.; Center for Astrophysics and Space Sciences, University of California at San Diego, MS 0424, La Jolla, CA 92093-0424 .)
Publication:
The Astrophysical Journal Supplement Series, Volume 149, Issue 1, pp. 1-28. (ApJS Homepage)
Publication Date:
11/2003
Origin:
UCP
ApJ Keywords:
Cosmology: Observations, Nuclear Reactions, Nucleosynthesis, Abundances, Galaxies: Quasars: Absorption Lines, Galaxies: Quasars: Individual: Alphanumeric: Q1243+3047
DOI:
10.1086/378152
Bibliographic Code:
2003ApJS..149....1K

Abstract

We report the detection of deuterium absorption at redshift 2.525659 toward Q1243+3047. We describe improved methods to estimate the deuterium to hydrogen abundance ratio (D/H) in absorption systems, including improved modeling of the continuum level, the Lyα forest, and the velocity structure of the absorption. Together with improved relative flux calibration, these methods give D/H=2.42+0.35-0.25×10-5 from our Keck I HIRES spectra of Q1243+3047, where the error is from the uncertainty in the shape of the continuum level and the amount of D absorption in a minor second component. The measured D/H is likely the primordial value because [O/H]=-2.79+/-0.05. This absorption system has a neutral hydrogen column density logNHI=19.73+/-0.04 cm-2, shows five D lines, and is mostly ionized. The best estimate of the primordial D/H is 2.78+0.44-0.38×10-5, from the logD/H-values toward five QSOs. The dispersion in the five values is larger than we expect from their individual measurement errors, and we suspect this is because some of these errors were underestimated. We observe a trend in D/H with logNHI that we also suspect is spurious. The best value for D/H is 0.6 σ smaller than we quoted in O'Meara et al. from three QSOs, and although we have more values, the error is similar because the dispersion is larger. In standard big bang nucleosynthesis (SBBN), the best D/H corresponds to a baryon-to-photon ratio η=5.9+/-0.5×10-10 and gives precise predictions for the primordial abundances of the other light nuclei. We predict more 4He than is reported in most measurements, although not more than allowed by some estimates of the systematic errors. We predict a 3He abundance very similar to that reported by Bania et al., and we predict 3-4 times more 7Li than is seen in halo stars. It is unclear if those stars could have destroyed this much of their 7Li. The η-value from D/H corresponds to a cosmological baryon density Ωbh2=0.0214+/-0.0020 (+/-9.3%), which agrees with the WMAP value of Ωbh2=0.0224+/-0.001.
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