Publication details for Dr Ryan CookeCooke, R. & Pettini, M. (2016). The primordial abundance of deuterium: ionization correction. Monthly Notices of the Royal Astronomical Society 455(2): 1512-1521.
- Publication type: Journal Article
- ISSN/ISBN: 0035-8711, 1365-2966
- DOI: 10.1093/mnras/stv2343
- Further publication details on publisher web site
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Author(s) from Durham
We determine the relative ionization of deuterium and hydrogen in low metallicity damped Lyman α (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 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. We provide a series of convenient fitting formulae to calculate the deuterium ionization correction based on observable quantities. The ionization correction typically does not exceed 0.1 per cent for metal-poor DLAs, which is comfortably below the current measurement precision (2 per cent). However, the deuterium ionization correction may need to be applied when a larger sample of D/H measurements becomes available.