Webb J K, Carswell R F, Lanzetta K M, Ferlet R, Lemoine M, Vidal-Madjar A, Bowen D V
School of Physics, University of New South Wales, Sydney, Australia.
Nature. 1997 Jul 17;388(6639):250-2. doi: 10.1038/40814.
Of the light elements, the primordial abundance of deuterium relative to hydrogen, (D/H)p, provides the most sensitive diagnostic for the cosmological mass density parameter, omegaB. Recent high-redshift D/H measurements are highly discrepant, although this may reflect observational uncertainties. The larger primordial D/H values imply a low omegaB (requiring the Universe to be dominated by non-baryonic matter), and cause problems for galactic chemical evolution models, which have difficulty in reproducing the steep decline in D/H to the present-day values. Conversely, the lower D/H values measured at high redshift imply an omegaB greater than that derived from 7Li and 4He abundance measurements, and may require a deuterium-abundance evolution that is too low to easily explain. Here we report the first measurement of D/H at intermediate redshift (z = 0.7010), in a gas cloud selected to minimize observational uncertainties. Our analysis yields a value of D/H ((2.0 +/- 0.5) x 10[-4]) which is at the upper end of the range of values measured at high redshifts. This finding, together with other independent observations, suggests that there may be inhomogeneity in (D/H)p of at least a factor of ten.
在轻元素中，氘相对于氢的原始丰度（D/H）p，为宇宙学质量密度参数ωB提供了最灵敏的诊断方法。近期的高红移D/H测量结果差异很大，不过这可能反映了观测的不确定性。较大的原始D/H值意味着较低的ωB（要求宇宙由非重子物质主导），并给星系化学演化模型带来问题，这些模型难以再现D/H急剧下降到当前值的情况。相反，在高红移处测得的较低D/H值意味着ωB大于从锂 - 7和氦 - 4丰度测量得出的值，并且可能需要一个过低的氘丰度演化，以至于难以轻松解释。在此，我们报告了在中等红移（z = 0.7010）下对D/H的首次测量，该测量是在一个经过挑选以最小化观测不确定性的气体云中进行的。我们的分析得出D/H的值为（(2.0 ± 0.5) × 10[-4]），这处于高红移处测量值范围的上限。这一发现与其他独立观测结果一起表明，原始（D/H）p可能存在至少十倍的不均匀性。
