JOYS: The [D/H] abundance derived from protostellar outflows across the Galactic disk measured with JWST

L. Francis; E. F. van Dishoeck; A. Caratti o Garatti; M. L. van Gelder; C. Gieser; H. Beuther; T. P. Ray L. Tychoniec; P. Nazari S. Reyes P. J. Kavanagh; P. Klaassen; M. Güdel; T. Henning

doi:10.1051/0004-6361/202451629

paper

JOYS: The [D/H] abundance derived from protostellar outflows across the Galactic disk measured with JWST

arXiv:2501.02085 · doi:10.1051/0004-6361/202451629

Abstract

The total deuterium abundance [D/H] in the universe is set by just two processes: the creation of deuterium in Big Bang Nucleosynthesis at an abundance of [D/H] $= 2.58 \pm 0.13 \times 1 0^{- 5}$ , and its destruction within stellar interiors. Measurements of the total [D/H] abundance can potentially provide a probe of Galactic chemical evolution, however, most measurements of [D/H] are only sensitive to the gas-phase deuterium, and the amount of deuterium sequestered in carbonaceous dust grains is debated. With the launch of JWST, it is now possible to measure the gas-phase [D/H] at unprecedented sensitivity and distances through observation of mid-IR lines of H $_{2}$ and HD. We employ data from the JWST Observations of Young protoStars (JOYS) program to measure the gas-phase [D/H] abundance with a rotation diagram analysis towards 5 nearby low-mass and 5 distant high-mass protostellar outflows. The gas-phase [D/H] varies between low-mass sources by up to a factor of $\sim 4$ , despite these sources likely having formed in a region of the Galactic disk that would be expected to have nearly constant total [D/H]. Most measurements of gas-phase [D/H] from our work or previous studies produce [D/H] $≲ 1.0 \times 1 0^{- 5}$ , a factor of $2 - 4$ lower than found from local UV absorption lines and as expected from Galactic chemical evolution models. The variations in [D/H] between our low-mass sources and the low [D/H] with respect to Galactic chemical evolution models suggest that our observations are not sensitive to the total [D/H]. Significant depletion of deuterium onto carbonaceous dust grains is a possible explanation, and tentative evidence of enhanced [D/H] towards shock positions with higher gas-phase Fe abundance is seen in the HH 211 outflow. Deeper observations of HD and H $_{2}$ in shocked environments and modelling of dust-grain destruction are warranted to test for the effects of depletion.

30 Pages, 20 Figures. Accepted for publication in Astronomy and Astrophysics

JOYS: The [D/H] abundance derived from protostellar outflows across the Galactic disk measured with JWST

Abstract

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