Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The deuterium-to-oxygen ratio in the interstellar medium   Because the ionization balances for HI, OI, and DI are locked together by
charge exchange, D/O is an important tracer for the value of the D/H ratio and
for potential spatial variations in the ratio. As the DI and OI column
densities are of similar orders of magnitude for a given sight line,
comparisons of the two values will generally be less subject to systematic
errors than comparisons of DI and HI, which differ by about five orders of
magnitude. Moreover, D/O is additionally sensitive to astration, because as
stars destroy deuterium, they should produce oxygen. We report here the results
of a survey of D/O in the interstellar medium performed with FUSE. We also
compare these results with those for D/N. Together with a few results from
previous missions, the sample totals 24 lines of sight. The distances range
from a few pc to ~2000 pc and log N(DI) from ~13 to ~16 (cm-2). The D/O ratio
is constant in the local interstellar medium out to distances of ~150 pc and
N(DI) ~ 1x10^15 cm-2, i.e. within the Local Bubble. In this region of the
interstellar space, we find D/O = (3.84+/-0.16)x10^-2 (1 sigma in the mean).
The homogeneity of the local D/O measurements shows that the spatial variations
in the local D/H and O/H must be extremely small, if any. A comparison of the
Local Bubble mean value with the few D/O measurements available for low
metallicity quasar sight lines shows that the D/O ratio decreases with cosmic
evolution, as expected. Beyond the Local Bubble we detected significant spatial
variations in the value of D/O. This likely implies a variation in D/H, as O/H
is known to not vary significantly over the distances covered in this study.
Our dataset suggests a present-epoch deuterium abundance below 1x10^-5, i.e.
lower than the value usually assumed, around 1.5x10^-5.

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The categories of this paper are: comp-gas
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The categories of this paper are: bayes-an
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The categories of this paper are: stat
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The categories of this paper are: solv-int
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The categories of this paper are: gr-qc
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The categories of this paper are: quant-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: funct-an
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-lat
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The categories of this paper are: chem-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: math-ph
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The categories of this paper are: cs
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The categories of this paper are: plasm-ph