AAS 205th Meeting, 9-13 January 2005
Session 57 Atomic Abundances in Interstellar Gas
Poster, Tuesday, January 11, 2005, 9:20am-6:30pm, Exhibit Hall

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[57.04] Can Dust Explain Observed Variations in Interstellar D/H?

B. T. Draine (Institute for Advanced Study)

The D/H ratio in interstellar gas varies on scales of a few hundred pc in the local Milky Way, with D/H values ranging from ~7\,ppm to ~22\,ppm. The reduction in D/H relative to the primordial value of D/H\,\approx26\,ppm is usually attributed to ``astration'' -- conversion of D into other elements by nuclear fusion in stars. However, it is shown here that astration has difficulty accounting for the observations because the expected associated variations in O/H are not seen.

The lower D/H values are instead likely due to ``depletion'' of the D onto dust grains. Polycyclic aromatic hydrocarbons (PAHs) are a possible repository for the missing D, and it appears possible for gas-grain reactions to achieve extreme deuteration of carbonaceous grain material. Grain destruction will release D from the grains; the gas phase abundance of D should therefore be positively correlated with the gas phase abundances of other elements that exhibit strong depletions, such as Mg, Si, Ti, and Fe, which also will be returned to the gas by grain destruction.

This work was supported in part by NSF grant AST-0406883.

If you would like more information about this abstract, please follow the link to http://arxiv.org/abs/astro-ph/0410310. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

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