Tracking The Post-BBN Evolution Of Deuterium

TL;DR

This paper discusses how deuterium abundance measurements from high-redshift systems and the local interstellar medium can test cosmological models and track the evolution of deuterium after Big Bang Nucleosynthesis.

Contribution

It provides a framework for comparing primordial deuterium abundance with post-BBN measurements to constrain cosmological and chemical evolution models.

Findings

Deuterium abundance in QSOALS constrains baryon density.

Post-BBN deuterium destruction bounds primordial levels.

Comparison with local ISM informs Galactic chemical evolution.

Abstract

The primordial abundance of deuterium produced during Big Bang Nucleosynthesis (BBN) depends sensitively on the universal ratio of baryons to photons, an important cosmological parameter probed independently by the Cosmic Microwave Background (CMB) radiation. Observations of deuterium in high-redshift, low-metallicity QSO Absorption Line Systems (QSOALS) provide a key baryometer, determining the baryon abundance at the time of BBN to a precision of 5%. Alternatively, if the CMB-determined baryon to photon ratio is used in the BBN calculation of the primordial abundances, the BBN-predicted deuterium abundance may be compared with the primordial value inferred from the QSOALS, testing the standard cosmological model. In the post-BBN universe, as gas is cycled through stars, deuterium is only destroyed so that its abundance measured anytime, anywhere in the Universe, bounds the primordial abundance from below. Constraints on models of post-BBN Galactic chemical evolution follow from a comparison of the relic deuterium abundance with the FUSE-inferred deuterium abundances in the chemically enriched, stellar processed material of the local ISM.