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The Deuterium Abundance Towards Q1937-1009

Astrophysics 2009-10-30 v1

Abstract

We present a new measurement of the deuterium-to-hydrogen ratio (D/H) in the Lyman limit absorption system at z=3.572z = 3.572 towards Q1937--1009. We use an improved method to measure D/H in QSO absorption systems, which includes extra parameters to treat the continuum uncertainties, a variety of new absorption models which allow for undetected velocity structure, and the improved measurement of the total hydrogen column density by Burles & Tytler (1997a). We find that all models, including contamination, give an upper limit D/H <3.9×105< 3.9 \times 10^{-5} (95 % confidence). Both this and previous analyses find contamination to be unlikely in this absorption system, A χ2\chi^2 analysis in models without contamination gives D/H =3.3±0.3×105= 3.3 \pm 0.3 \times 10^{-5} (67% confidence), which is higher but consistent with the earlier results of Tytler et al. (1996), and a second measurement of D/H towards Q1009+2956 (Burles & Tytler 1997). With calculations of standard big bang nucleosynthesis (SBBN) and the assumption that this measurement of D/H is representative of the primordial value, we find a high baryon-to-photon ratio, η=5.3±0.4×1010\eta = 5.3 \pm 0.4 \times 10^{-10}. This is consistent with primordial abundance determinations of 4^4He in H II regions (Izotov et al. 1997) and 7^7Li in the atmospheres of warm metal-poor population II stars (Bonifacio & Molaro 1997). We find a high value for the present-day baryon density, Ωbh2=0.0193±0.0014\Omega_b h^2 = 0.0193 \pm 0.0014, which is consistent with other inventories of baryonic matter, from low to high redshift: clusters of galaxies, the Lyman alpha forest & the Cosmic Microwave Background.

Keywords

Cite

@article{arxiv.astro-ph/9712108,
  title  = {The Deuterium Abundance Towards Q1937-1009},
  author = {Scott Burles and David Tytler},
  journal= {arXiv preprint arXiv:astro-ph/9712108},
  year   = {2009}
}

Comments

49 pages, 19 figures, to appear in the Astrophysical Journal