Cooke, Ryan J. and Pettini, Max and Jorgenson, Regina A. and Murphy, Michael T. and Steidel, Charles C. (2014) Precision Measures of the Primordial Abundance of Deuterium. Astrophysical Journal, 781 (1). Art. No. 31. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20140207-112247242
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We report the discovery of deuterium absorption in the very metal-poor ([Fe/H] = –2.88) damped Lyα system at z_abs = 3.06726 toward the QSO SDSS J1358+6522. On the basis of 13 resolved D I absorption lines and the damping wings of the H I Lyα transition, we have obtained a new, precise measure of the primordial abundance of deuterium. Furthermore, to bolster the present statistics of precision D/H measures, we have reanalyzed all of the known deuterium absorption-line systems that satisfy a set of strict criteria. We have adopted a blind analysis strategy (to remove human bias) and developed a software package that is specifically designed for precision D/H abundance measurements. For this reanalyzed sample of systems, we obtain a weighted mean of (D/H)_p = (2.53 ± 0.04) × 10^–5, corresponding to a universal baryon density 100 Ω_b, 0 h^2 = 2.202 ± 0.046 for the standard model of big bang nucleosynthesis (BBN). By combining our measure of (D/H)p with observations of the cosmic microwave background (CMB), we derive the effective number of light fermion species, N eff = 3.28 ± 0.28. We therefore rule out the existence of an additional (sterile) neutrino (i.e., N_eff = 4.046) at 99.3% confidence (2.7σ), provided that the values of N eff and of the baryon-to-photon ratio (η_10) did not change between BBN and recombination. We also place a strong bound on the neutrino degeneracy parameter, independent of the 4He primordial mass fraction, Y P: ξD = +0.05 ± 0.13 based only on the CMB+(D/H)_p observations. Combining this value of ξD with the current best literature measure of Y P, we find a 2σ upper bound on the neutrino degeneracy parameter, |ξ| ≤ +0.062.
|Additional Information:||© 2014 The American Astronomical Society. Received 2013 August 14; accepted 2013 November 13; published 2014 January 3. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (VLT program IDs: 68.B-0115(A), 70.A-0425(C), 078.A-0185(A), 085.A-0109(A)), and at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Keck telescope time was partially granted by NOAO, through the Telescope System Instrumentation Program (TSIP). TSIP is funded by NSF. We are grateful to the staff astronomers at the ESO VLT and Keck Observatory for their assistance with the observations. We are indebted to Gary Steigman for kindly communicating ahead of publication the latest fitting formulae used in this work, and for providing valuable comments on the manuscript. We also thank an anonymous referee who provided useful suggestions that improved the presentation of this work. Discussions, advice, and help with various aspects of the work described in this paper were provided by Antony Lewis, Jordi Miralda-Escudé, Paolo Molaro, Ken Nollett, Pasquier Noterdaeme, John O’Meara, Jason X. Prochaska, Signe Riemer-Sørenson, Donatella Romano, and John Webb. We thank the Hawaiian people for the opportunity to observe from Mauna Kea; without their hospitality, this work would not have been possible. R.J.C. is partially supported by NSF grant AST-1109447. R.A.J. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1102683. M.T.M. thanks the Australian Research Council for a QEII Research Fellowship (DP0877998) and a Discovery Project grant (DP130100568).|
|Subject Keywords:||cosmology: observations; primordial nucleosynthesis; quasars: absorption lines|
|Official Citation:||Precision Measures of the Primordial Abundance of Deuterium Ryan J. Cooke et al. 2014 ApJ 781 31|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||08 Feb 2014 00:21|
|Last Modified:||08 Feb 2014 00:21|
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