JOYS: The [D/H] abundance derived from protostellar outflows across the Galactic disk measured with JWST
Journal
Date Issued
2025
Author(s)
L. Francis
•
E. F. van Dishoeck
•
•
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
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]$=2.58\pm0.13\times10^{-5}$, 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 $\sim4$, 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] $\lesssim
1.0\times10^{-5}$, 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.
Volume
694
Start page
A174
Issn Identifier
0004-6361
Rights
open.access
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