Journal Article

The deuterium abundance in the local interstellar medium

Tijana Prodanović, Gary Steigman and Brian D. Fields

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 406, issue 2, pages 1108-1115
Published in print August 2010 | ISSN: 0035-8711
Published online July 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16734.x
The deuterium abundance in the local interstellar medium

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As the Galaxy evolves, the abundance of deuterium in the interstellar medium (ISM) decreases from its primordial value: deuterium is ‘astrated’. The deuterium astration factor fD, the ratio of the primordial D abundance (the D to H ratio by number) to the ISM D abundance, is determined by the competition between stellar destruction and infall, providing a constraint on models of the chemical evolution of the Galaxy. Although conventional wisdom suggests that the local ISM (i.e. within ∼1–2 kpc of the Sun) should be well mixed and homogenized on time-scales short compared to the chemical evolution time-scale, the data reveal gas-phase variations in the deuterium, iron and other metal abundances as large as factors of ∼4–5 or more, complicating the estimate of the ‘true’ ISM D abundance and of the deuterium astration factor. Here, assuming that the variations in the observationally inferred ISM D abundances result entirely from the depletion of D on to dust, rather than from unmixed accretion of nearly primordial material, a model-independent, Bayesian approach is used to determine the undepleted abundance of deuterium in the ISM (or a lower limit to it). We find the best estimate for the undepleted, ISM deuterium abundance to be (D/H)ISM≥ (2.0 ± 0.1) × 10−5. This result is used to provide an estimate of (or an upper bound to) the deuterium astration factor, fD≡ (D/H)P/(D/H)ISM≤ 1.4 ± 0.1.

Keywords: ISM: abundances; Galaxy: evolution; galaxies: ISM

Journal Article.  6942 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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