Deuterium link: From interstellar medium and chemical evolution to cosmology and structure formation

Deuterium has a special place in cosmology, nuclear astrophysics, and galactic chemical evolution, because of its unique property that it is only created in the big bang nucleosynthesis while all other processes result in its net destruction. However, a large scatter found in the interstellar medium (ISM) deuterium abundance measurements indicates that deuterium might be preferentially depleted onto dust grains, which complicates the use of deuterium as a probe of galactic chemical evolution (GCE) models. We have applied a model-independent, statistical Bayesian method and determined the true, undepleted ISM D abundance. Having found the ISM D abundance, one can identify the successful GCE models, which can then be used to learn about nucleosynthesis in the ISM, but can also be placed in cosmological context to learn about the infall rates of the primordial gas to our Galaxy, which bares implications for models of galaxy formation. Here we present our results and their implications for discriminating between different GCE models, for our understanding of the nature and physics of interstellar dust grains, as well as implications for cosmological evolution.