A robust deuterium abundance; Re-measurement of the z=3.256 absorption
  system towards the quasar PKS1937-1009
  The primordial deuterium abundance is an important tracer of the fundamental
physics taking place during Big Bang Nucleosynthesis. It can be determined from
absorption features along the line of sight to distant quasars. The quasar
PKS1937-1009 contains two absorptions systems that have been used to measure
the primordial deuterium abundance, the lower redshift one being at z_abs =
3.256. New observations of this absorber are of a substantially higher
signal-to-noise and thus permit a significantly more robust estimate of the
primordial deuterium abundance, leading to a D/H ratio of 2.45+/-0.28 x10^-5.
Whilst the precision of the new measurement presented here is below that
obtained from the recent cosmological parameter measurements by Planck, our
analysis illustrates how a statistical sample obtained using similarly high
spectral signal-to-noise can make deuterium a competitive and complementary
cosmological parameter estimator and provide an explanation for the scatter
seen between some existing deuterium measurements.
