The Primordial Abundance of Deuterium: Ionization correction

Understand

We determine the relative ionization of deuterium and hydrogen in low metallicity damped Lyman-alpha (DLA) and sub-DLA systems using a detailed suite of photoionization simulations.

• We model metal-poor DLAs as clouds of gas in pressure equilibrium with a host dark matter halo, exposed to the Haardt & Madau (2012) background radiation of galaxies and quasars at redshift z~3.
• Our results indicate that the deuterium ionization correction correlates with the H I column density and the ratio of successive ion stages of the most commonly observed metals.
• The N(N II) / N(N I) column density ratio provides the most reliable correction factor, being essentially independent of the gas geometry, H I column density, and the radiation field.