Deuterium to hydrogen towards QSO 1009+2956 from a mesoturbulent model

Abstract

Abstract We present a new analysis of the deuterium absorption at z = 2.504 towards the quasar Q1009+2956 using the mesoturbulent model which accounts for possible correlations in the large-scale velocity field. We obtain a slightly higher deuterium-to-hydrogen ratio D/H ≈ (3.5–5.0) × 10−5 as compared with the recent measurement D/H ≈ (3.3–4.5) × 10−5 (68% C.L.) performed by Burles and Tytler (1998b) using the usual microturbulent approximation which assumes that the velocity field is uncorrelated. Other mesoturbulent calculations of the D-abundances at z = 3.572 towards Q1937–1009 and at z = 0.701 towards Q1718+4807 (the systems showing ‘low’ and possibly ‘high’ D/H values, respectively, in the microturbulent approaches) agree with the present one with the errors of measurements. Thus, the mesoturbulent analysis does not reveal any spatial variations of D/H and supports the standard homogeneous model of big bang nucleosynthesis.