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A high deuterium abundance at redshift z = 0.7
J K Webb1, R F Carswell, K M Lanzetta
1School of Physics, University of New South Wales, Sydney, Australia.
Nature
|July 17, 1997
Summary
Primordial deuterium-to-hydrogen (D/H) measurements are discrepant. This study reports a new intermediate-redshift D/H value suggesting significant inhomogeneity in the early universe
Area of Science:
- Cosmology
- Astrophysics
- Nuclear Physics
Background:
- Primordial deuterium-to-hydrogen ratio (D/H)p is a key diagnostic for the cosmological mass density parameter, omegaB.
- Existing high-redshift D/H measurements show significant discrepancies, potentially due to observational uncertainties.
- Discrepant D/H values pose challenges for cosmological models and galactic chemical evolution.
Purpose of the Study:
- To report the first measurement of the D/H ratio at intermediate redshift (z = 0.7010).
- To investigate potential inhomogeneity in the primordial D/H abundance.
- To provide a value that can help resolve discrepancies in cosmological parameter estimations.
Main Methods:
- Selected a gas cloud at intermediate redshift (z = 0.7010) to minimize observational uncertainties.
- Measured the deuterium-to-hydrogen ratio (D/H) in the selected gas cloud.
- Analyzed the D/H value in the context of existing high-redshift measurements and cosmological models.
Main Results:
- A D/H value of (2.0 +/- 0.5) x 10[-4] was measured at z = 0.7010.
- This measured value falls at the upper end of the range observed for high-redshift measurements.
- The results, combined with other observations, suggest possible inhomogeneity in (D/H)p by at least a factor of ten.
Conclusions:
- The findings support the hypothesis of significant inhomogeneity in the primordial deuterium abundance.
- This inhomogeneity has implications for the interpretation of D/H measurements as a cosmological probe.
- Further measurements are needed to confirm the extent and implications of (D/H)p variations.
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