Deuterium/hydrogen in a new Lyman limit absorption system at z=3.256 towards PKS1937-1009

Author(s): Crighton, NHM; Webb, JK; Ortiz-Gil, A; et al.

Source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY  Volume: 355   Issue: 4   Pages: 1042-1052   DOI: 10.1111/j.1365-2966.2004.08390.x   Published: DEC 21 2004

We have identified a new Lyman limit absorption system towards PKS1937-1009, with log N(H I) = 18.25 +/- 0.02 at z = 3.256 that is suitable for measuring deuterium/hydrogen (D/H). We find a 68.3 per cent confidence range for D/H of 1.6(-0.30)(+0.25) x 10(-5) and a 95.4 per cent range of 1.6(-0.4)(+0.5) x 10(-5). The metallicity of the cloud where D/H was measured is low, [Si/H] = -2.0 +/- 0.5. At these metallicities we expect that D/H will be close to the primordial value. Our D/H is lower than the D/H value predicted using the Omega(b) calculated from the cosmic background radiation measured by the Wilkinson Microwave Anisotropy Probe, 2.60(-0.17)(+0.19) x 10(-5). Our result also exacerbates the scatter in D/H values around the mean primordial D/H.