Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: G305.136+0.068: A massive and dense cold core in an early stage of
  evolution   We report molecular line observations, made with ASTE and SEST, and dust
continuum observations at 0.87 mm, made with APEX, towards the cold dust core
G305.136+0.068. The molecular observations show that the core is isolated and
roughly circularly symmetric and imply that it has a mass of
$1.1\times10^3~M_\odot$. A simultaneous model fitting of the spectra observed
in four transitions of CS, using a non-LTE radiative transfer code, indicates
that the core is centrally condensed, with the density decreasing with radius
as $r^{-1.8}$, and that the turbulent velocity increases towards the center.
The dust observations also indicate that the core is highly centrally condensed
and that the average column density is 1.1 g cm$^{-2}$, value slightly above
the theoretical threshold required for the formation of high mass stars. A fit
to the spectral energy distribution of the emission from the core indicates a
dust temperature of $17\pm2$ K, confirming that the core is cold. Spitzer
images show that the core is seen in silhouette from 3.6 to 24.0 $\mu$m and
that is surrounded by an envelope of emission, presumably tracing an externally
excited photo-dissociated region. We found two embedded sources within a region
of 20" centered at the peak of the core, one of which is young, has a
luminosity of $66~L_\odot$ and is accreting mass with a high accretion rate, of
$\sim1\times10^{-4}~M_\odot$ yr$^{-1}$. We suggest that this object corresponds
to the seed of a high mass protostar still in the process of formation. The
present observations support the hypothesis that G305.136+0.068 is a massive
and dense cold core in an early stage of evolution, in which the formation of a
high mass star has just started.

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The categories of this paper are: cs
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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: math
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The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
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The categories of this paper are: bayes-an
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The categories of this paper are: acc-phys
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The categories of this paper are: cmp-lg
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The categories of this paper are: nlin
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The categories of this paper are: econ
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The categories of this paper are: stat
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The categories of this paper are: supr-con
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The categories of this paper are: adap-org
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The categories of this paper are: hep-ex
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The categories of this paper are: q-bio