A robust deuterium abundance; Re-measurement of the z=3.256 absorption system towards the quasar PKS1937-1009

TL;DR

This paper presents a new high signal-to-noise measurement of the primordial deuterium abundance from a quasar absorption system, demonstrating its potential as a competitive cosmological parameter and addressing discrepancies in previous measurements.

Contribution

It provides a more robust deuterium abundance estimate using high-quality data and discusses its implications for cosmology and existing measurement scatter.

Findings

New D/H ratio: 2.45±0.28 x10^-5

High signal-to-noise data improves measurement robustness

Deuterium can be a competitive cosmological parameter

Abstract

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.