Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The initial conditions of isolated star formation: IV - C18O
  observations and modelling of the pre-stellar core L1689B   We present C18O observations of the pre-stellar core L1689B, in the (J=3-2)
and (J=2-1) rotational transitions, taken at the James Clerk Maxwell Telescope
in Hawaii. We use a lambda-iteration radiative transfer code to model the data.
We adopt a similar form of radial density profile to that which we have found
in all pre-stellar cores, with a `flat' inner profile, steepening towards the
edge, but we make the gradient of the `flat' region a free parameter. We find
that the core is close to virial equilibrium, but there is tentative evidence
for core contraction. We allow the temperature to vary with a power-law form
and find we can consistently fit all of the CO data with an inverse temperature
gradient that is warmer at the edge than the centre. However, when we combine
the CO data with the previously published millimetre data we fail to find a
simultaneous fit to both data-sets without additionally allowing the CO
abundance to decrease towards the centre. This effect has been observed
qualitatively many times before, as the CO freezes out onto the dust grains at
high densities, but we quantify the effect. Hence we show that the combination
of mm/submm continuum and spectral line data is a very powerful method of
constraining the physical parameters of cores on the verge of forming stars.

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The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
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The categories of this paper are: bayes-an
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The categories of this paper are: q-fin
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The categories of this paper are: atom-ph
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
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The categories of this paper are: eess
10
The categories of this paper are: q-bio