Key points are not available for this paper at this time.
We report the measurement of the primordial D/H abundance ratio towards QSO. The column density of the hydrogen in the z 2. 536 Lyman limit system is high, = 19. 422 0. 009, allowing for the deuterium to be seen in 5 Lyman series transitions. The measured value of the D/H ratio towards QSO is found to be D/H = 2. 54 0. 23 10^-5. The metallicity of the system showing D/H is found to be 0. 01 solar, indicating that the measured D/H is the primordial D/H within the measurement errors. The gas which shows D/H is neutral, unlike previous D/H systems which were more highly ionized. Thus, the determination of the D/H ratio becomes more secure since we are measuring it in different astrophysical environments, but the error is larger because we now see more dispersion between measurements. Combined with prior measurements of D/H, the best D/H ratio is now D/H = 3. 0 0. 4 10^-5, which is 10% lower than the previous value. The new values for the baryon to photon ratio, and baryonic matter density derived from D/H are = 5. 6 0. 5 10^-10 and =0. 0205 0. 0018 respectively.
O’Meara et al. (Thu,) studied this question.