The primordial deuterium abundance: subDLA system at z_abs=2.437 towards the QSO J1444+2919
We report a new detection of neutral deuterium in the sub Damped Lyman Alpha system with low metallicity [O/H]=−2.042±0.005 at z_abs=2.437 towards QSO J1444
+2919. The hydrogen column density in this system is logN=19.983±0.010 and the measured value of deuterium abundance is log(D/H)=−4.706±0.007stat±0.067syst. This system meets the set of strict selection criteria stated recently by Cooke et al. and, therefore, widens the Precision Sample of D/H. However, possible underestimation of systematic errors can bring bias into the mean D/H value (especially if use a weighted mean). Hence, it might be reasonable to relax these selection criteria and, thus, increase the number of acceptable absorption systems with measured D/H values. In addition, an unweighted mean value might be more appropriate to describe the primordial deuterium abundance. The unweighted mean value of the whole D/H data sample available to date (15 measurements) gives a conservative value of the primordial deuterium abundance (D/H)
p=(2.55±0.19)×10−5 which is in good agreement with the prediction of analysis of the cosmic microwave background radiation for the standard Big Bang nucleosynthesis. By means of the derived (D/H)p value the baryon density of the Universe Ωbh2=0.0222±0.0013 and the baryon-to-photon ratio η10=6.09±0.36 have been deduced. These values have confident intervals which are less stringent than that obtained for the Precision Sample and, thus, leave a broader window for new physics. The latter is particularly important in the light of the lithium problem