1997/07/17 by J. K. Webb, John K. Webb, R. F. Carswell +9 · 6 citations
Earth and Planetary Sciences · Physics and Astronomy · #Atmospheric Ozone and Climate #Geophysics and Gravity Measurements #Scientific Research and Discoveries #astro-ph
paper · pdf · doi:10.1038/40814
published as Nature 388 (1997) 250 · 6 pages, 1 figure
openalex publication_date 1997/07/17 · arxiv created 1997/08/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Of the light elements, the primordial abundance of deuterium, (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 (D/H) values, which imply a low OmegaB and require the Universe to be dominated by non-baryonic matter (dynamical studies indicate a higher total density parameter), cause problems for galactic chemical evolution models since they have difficulty in reproducing the large decline down to the lower present-day (D/H). Conversely, low (D/H) values imply an OmegaB greater than 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 at intermediate redshift, where the observational difficulties are smaller, of a gas cloud with ideal characteristics for this experiment. Our analysis of the z = 0.7010 absorber toward 1718+4807 indicates (D/H) = 2.0 +/- 0.5 x 10-4 which is in the high range. This and other independent observations suggests there may be a cosmological inhomogeneity in (D/H)p of at least a factor of ten.