Turn-off of Deuterium Astration in the Recent Star Formation of the Galaxy Disk

TL;DR

This paper proposes a new model explaining the recent high deuterium abundance in the Galaxy by suggesting that declining star formation and ongoing gas infall suppress deuterium destruction, challenging previous models predicting continuous decrease.

Contribution

It introduces a novel chemical evolution model that accounts for the recent D/H enhancement by incorporating declining star formation and gas infall effects.

Findings

Recent D/H measurements are consistent with ongoing gas infall.

Deuterium astration is suppressed in the recent Gyr according to the model.

The model challenges traditional predictions of monotonic D/H decrease.

Abstract

Chemical features of the local stellar disk have firmly established that long-term, continuous star formation has been accompanied by a steady rate of accretion of low-metallicity gas from the halo. We now argue that the recent discovery of an enhanced deuterium (D) fraction in the Galaxy is consistent with this picture. We consider two processes: the destruction of D in the interior of stars (astration) and the supply of nearly primordial D associated with the gas infall. Conventional Galactic chemical evolution models predict a monotonic decrease in D/H with time with a present-day D/H abundance which is much lower than the local value recently revealed. This predicted feature is the result of high levels of deuterium astration involved in the formation of the local metal-enhanced disk. Here we propose a new channel to explain the observed enhancement in D/H. Our model, which invokes ongoing gaseous infall and a star formation rate that declines over the past several Gyr, predicts that the D astration is suppressed over the same time interval.