Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Near-Infrared Imaging Survey of Coalsack Globule 2   We describe a near-infrared imaging survey of Globule 2 in the Coalsack. This
Bok globule is the highest density region of this southern hemisphere molecular
cloud and is the most likely location for young stars in this complex. The
survey is complete for K < 14.0, H < 14.5, and J < 15.5, several magnitudes
more sensitive than previous observations of this globule. From the large
number of background stars, we derive an accurate near-infrared extinction law
for the cloud. Our result, E_{J-H}/E_{H-K} = 2.08 \pm 0.03, is significantly
steeper than results for other southern clouds. We use the J-H/H-K color-color
diagram to identify two potential young stars with K < 14.0 in the region. We
apply H-band star counts to derive the density profile of the Coalsack Globule
2 and use a polytropic model to describe the internal structure of this small
cloud. For a gas temperature T \sim 15 K, this globule is moderately unstable.

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The categories of this paper are: cond-mat
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The categories of this paper are: math
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The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex
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The categories of this paper are: q-fin
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The categories of this paper are: solv-int
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The categories of this paper are: funct-an
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The categories of this paper are: gr-qc
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The categories of this paper are: q-bio
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: econ
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The categories of this paper are: acc-phys
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The categories of this paper are: comp-gas