A new precise determination of the primordial abundance of deuterium: measurement in the metal-poor sub-DLA system at <i>z</i> = 3.42 towards quasar J 1332+0052
P. A. Kislitsyn, S. A. Balashev, M. T. Murphy, C. Ledoux, P. Noterdaeme, A. V. Ivanchik
Abstract
ABSTRACT The theory of Big Bang nucleosynthesis, coupled with an estimate of the primordial deuterium abundance (D/H)pr, offers insights into the baryon density of the Universe. Independently, the baryon density can be constrained during a different cosmological era through the analysis of cosmic microwave background anisotropy. The comparison of these estimates serves as a rigorous test for the self-consistency of the standard cosmological model and stands as a potent tool in the quest for new physics beyond the standard model of particle physics. For a meaningful comparison, a clear understanding of the various systematic errors affecting deuterium measurements is crucial. Given the limited number of D/H measurements, each new estimate carries significant weight. This study presents the detection of D i absorption lines in a metal-poor sub-Damped Lyman-α system ($\rm [O/H]=-1.71\pm 0.02$, log N(H i) = 19.304 ± 0.004) at zabs = 3.42 towards the quasar SDSS J133254.51+005250.6. Through simultaneous fitting of H i and D i Lyman-series lines, as well as low-ionization metal lines, observed at high spectral resolution and high signal-to-noise using VLT/UVES and Keck/HIRES, we derive log (D i/H i) = −4.622 ± 0.014, accounting for statistical and systematic uncertainties of 0.008dex and 0.012 dex, respectively. Thanks to negligible ionization corrections and minimal deuterium astration at low metallicity, this D/H ratio provides a robust measurement of the primordial deuterium abundance, consistent and competitive with previous works. Incorporating all prior measurements, the best estimate of the primordial deuterium abundance is constrained as: (D/H)pr = (2.533 ± 0.024) × 10−5. This represents a 5 per cent improvement in precision over previous studies and reveals a moderate tension with the expectation from the standard model (≈2.2σ). This discrepancy underscores the importance of further measurements in the pursuit of new physics.