Deuterium in the interstellar medium

Abstract

Deuterium is only created in the Big Bang nucleosynthesis while all other processes destroy it. Because of this unique property, deuteriumhas for a long time served as the key to determining important cosmological parameters, before modern observations of cosmic microwave background were available. Moreover, given the net destruction of deuterium with time, its remaining abundance in the interstellar medium is a direct probe of how much gas was processed through stars, and can thus serve as an important tool in the galactic chemical evolutionmodeling as well. However, in the past decade, observations of deuterium in the interstellar medium have revealed large variations of its gas-phase abundance, which called in question our understanding of deuterium, galactic chemical evolution, and even modern cosmology. As a solution to this crisis, it was suggested that deuterium might be depleted onto dust grains, however not all observation and models agree with this potential explanation. Presented in this chapter will be a review of the current state of affairs related to this persisting and crucial problem with deuterium abundance in the interstellar medium, whose solution will bare important consequences for galactic chemical evolution models, our understanding of the nucleosynthesis and dust formation in the interstellar medium, as well as for the larger cosmological context and models of galaxy formation. PACS 05.45-a, 52.35.Mw, 96.50.Fm. © 2012 by Nova Science Publishers, Inc. All rights reserved.