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A high deuterium abundance at redshift z = 0.7
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Journal Article
A high deuterium abundance at redshift z = 0.7
1997
Overview
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.
Publisher
Nature Publishing,Nature Publishing Group
Subject
/ Characteristics and properties of external galaxies and extragalactic objects
/ Exact sciences and technology
/ Extraterrestrial Environment
/ Hydrogen
/ Intergalactic matter ; quasar absorption and emission-line systems ; lyman forest
/ Stellar systems. Galactic and extragalactic objects and systems. The universe
