The Cosmological Baryon Density from the Deuterium‐to‐Hydrogen Ratio in QSO Absorption Systems: D/H toward Q1243+3047

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 Ly forest, and the velocity structure of the absorption. Together with improved relative flux calibration, these methods give D=H ¼ 2:42 À0:38 Â 10 À5 , from the log D/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 log N H i that we also suspect is spurious. The best value for D/H is 0.6 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 ¼ 5:9 AE 0:5 Â 10 À10 and gives precise predictions for the primordial abundances of the other light nuclei. We predict more 4 He than is reported in most measurements, although not more than allowed by some estimates of the systematic errors. We predict a 3 He abundance very similar to that reported by Bania et al., and we predict 3-4 times more 7 Li than is seen in halo stars. It is unclear if those stars could have destroyed this much of their 7 Li. The -value from D/H corresponds to a cosmological baryon density b h 2 ¼ 0:0214 AE 0:0020 (AE9.3%), which agrees with the WMAP value of b h 2 ¼ 0:0224 AE 0:001.

Detector Simulation and WIMP Search Analysis for the Cryogenic Dark Matter Search Experiment

“…The theory underlying BBN provides a detailed description of the production of heavier elements in a hot, dense soup of baryons in an expanding, cooling universe, and observation of the relative abundances of these elements today thus provides information about the initial density of baryons (protons and neutrons) in the universe. systematic errors in these measurements and in relating these measurements to the primordial populations [16]. Despite the discrepancy between elements, the value of Ω b ≈ 0.04 compared with other measurements indicating Ω m ≈ 0.24 implies that 5/6 of the matter content of the universe is in non-baryonic forms.…”

“…These Doppler shifts can be measured at various radii from the galactic center, and correcting the data for the inclination of the galaxy to the observer's line of sight provides the 'galactic rotation curve', the rotational 48 and predictions from a number of researchers, please see [16].…”

Big Bang Nucleosynthesis

“…It shows that the agreement is perfect for deuterium: when using the WMAP baryonic density, SBBN gives D/H = (2.60 +0. 19 −0.17 ) × 10 −5 to be compared with the average value (2.78 +0.44 −0.38 ) × 10 −5 of D/H observations in cosmological clouds [23]. The exact convergence between these two independent methods is claimed to reinforce the confidence in the deduced Ω b ·h 2 value.…”

Observational constraints to a unified cosmological model

“…According to the Big Bang model, the nuclei of the light elements -hydrogen (H), deuterium (D), 3 He, 4 He e 7 Li -were created in the first minutes of the Universe during a phase known as the primordial nucleosynthesis [44]. The abundances of these light elements depend on the present-day value of the baryon density parameter Ω b0 and on the Hubble constant H 0 [45].…”

“…Ref. [47] suggests to determine this ratio using information from a special type of high-redshift quasar (QSO), more specifically through damped Lyman alpha systems (DLA) spectra [44,[48][49][50]. 3 The deuterium to hydrogen abundance ratio was given as (D/H) = (2.535 ± 0.05) × 10 −5 by Ref.…”