期刊
ASTROPHYSICAL JOURNAL
卷 830, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.3847/0004-637X/830/2/148
关键词
cosmology: observations; cosmology: theory; primordial nucleosynthesis; quasars: absorption lines; quasars: individual ( J1358+0349)
资金
- NASA through Hubble Fellowship [HST-HF-51338.001-A]
- Space Telescope Science Institute
- Association of Universities for Research in Astronomy, Inc. [NAS5-26555]
- NSF Astronomy and Astrophysics Postdoctoral Fellowship [AST-1102683]
We report the discovery and analysis of the most metal-poor damped Ly alpha (DLA) system currently known, which also displays the Lyman series absorption lines of neutral deuterium. The average [O/H] abundance of this system is [O/H]. =. -2.804 +/- 0.015, which includes an absorption component with [O/H]. =. -3.07 +/- 0.03. Despite the unfortunate blending of many weak D I absorption lines, we report a precise measurement of the deuterium abundance of this system. Using the six highest-quality and self-consistently analyzed measures of D/H in DLAs, we report tentative evidence for a subtle decrease of D/H with increasing metallicity. This trend must be confirmed with future high-precision D/H measurements spanning a range of metallicity. A weighted mean of these six independent measures provides our best estimate of the primordial abundance of deuterium, 10(5) (D/H)(P) = 2.547 +/- 0.033 (log(10)(D/H)(P) = -4.5940 +/- 0.0056). We perform a series of detailed Monte Carlo calculations of Big Bang nucleosynthesis (BBN) that incorporate the latest determinations of several key nuclear reaction cross-sections, and propagate their associated uncertainty. Combining our measurement of (D/H) P with these BBN calculations yields an estimate of the cosmic baryon density, 100 Omega(B,0)h(2)(BBN) = 2.156 +/- 0.020, if we adopt the most recent theoretical determination of the d(p, gamma)He-3 reaction rate. This measure of Omega(B,0)h(2) differs by similar to 2.3 sigma from the Standard Model value estimated from the Planck observations of the cosmic microwave background. Using instead a d(p, gamma)He-3 reaction rate that is based on the best available experimental cross-section data, we estimate 100 Omega(B,0) h(2)(BBN) = 2.260 +/- 0.034, which is in somewhat better agreement with the Planck value. Forthcoming measurements of the crucial d(p, gamma)He-3 cross-section may shed further light on this discrepancy.
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