The primordial abundance of deuterium: ionization correction

Cooke, R.; Pettini, M.

Abstract

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.

Citation

Cooke, R., & Pettini, M. (2016). The primordial abundance of deuterium: ionization correction. Monthly Notices of the Royal Astronomical Society, 455(2), 1512-1521. https://doi.org/10.1093/mnras/stv2343

• Journal Article Type: Article
• Acceptance Date: Oct 6, 2016
• Online Publication Date: Nov 17, 2016
• Publication Date: Nov 17, 2016
• Deposit Date: Feb 20, 2017
• Publicly Available Date: Feb 22, 2017
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 455
• Issue: 2
• Pages: 1512-1521
• DOI: https://doi.org/10.1093/mnras/stv2343
• Public URL: https://durham-repository.worktribe.com/output/1385672
• Related Public URLs: http://adsabs.harvard.edu/abs/2016MNRAS.455.1512C