Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Upper limit for the D2H+ ortho-to-para ratio in the prestellar core
  16293E (CHESS)   The H3+ ion plays a key role in the chemistry of dense interstellar gas
clouds where stars and planets are forming. The low temperatures and high
extinctions of such clouds make direct observations of H3+ impossible, but lead
to large abundances of H2D+ and D2H+, which are very useful probes of the early
stages of star and planet formation. The ground-state rotational ortho-D2H+
111-000 transition at 1476.6 GHz in the prestellar core 16293E has been
searched for with the Herschel/HIFI instrument, within the CHESS (Chemical
HErschel Surveys of Star forming regions) Key Program. The line has not been
detected at the 21 mK km/s level (3 sigma integrated line intensity). We used
the ortho-H2D+ 110-111 transition and para-D2H+ 110-101 transition detected in
this source to determine an upper limit on the ortho-to-para D2H+ ratio as well
as the para-D2H+/ortho-H2D+ ratio from a non-LTE analysis. The comparison
between our chemical modeling and the observations suggests that the CO
depletion must be high (larger than 100), with a density between 5e5 and 1e6
cm-3. Also the upper limit on the ortho-D2H+ line is consistent with a low gas
temperature (~ 11 K) with a ortho-to-para ratio of 6 to 9, i.e. 2 to 3 times
higher than the value estimated from the chemical modeling, making it
impossible to detect this high frequency transition with the present state of
the art receivers.

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The categories of this paper are: hep-lat
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The categories of this paper are: cond-mat
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The categories of this paper are: gr-qc
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The categories of this paper are: eess
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The categories of this paper are: physics
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The categories of this paper are: hep-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
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The categories of this paper are: solv-int
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: quant-ph
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The categories of this paper are: cs
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The categories of this paper are: nucl-ex
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The categories of this paper are: nlin
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The categories of this paper are: bayes-an