A high deuterium abundance at redshift z = 0.7

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.