Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dust Extinction and Molecular Cloud Structure: L977   We report results of a near--infrared imaging survey of L977, a dark cloud in
Cygnus seen in projection against the plane of the Milky Way. We use
measurements of the near--infrared color excess and positions of the 1628
brightest stars in our survey to measure directly dust extinction through the
cloud following the method described by Lada et al. (1994). We spatially
convolve the individual extinction measurements with a square filter 90" in
size to construct a large-scale map of extinction in the cloud. We derive a
total mass of M(L977)= (660 +/- 30)(D/500 pc)^2 Msun and, via a comparison of
source counts with predictions of a galactic model, estimate a distance to L977
of 500 +/- 100 pc. We find a correlation between the measured dispersion in our
extinction determinations and the extinction. We interpret this as evidence for
the presence of structure on scales smaller than the 90" resolution of our
extinction map.
  To further investigate the structure of the cloud we construct the frequency
distribution of the 1628 individual extinction measurements in the L977 cloud.
The shape of the distribution is similar to that of the IC 5146 cloud. Monte
Carlo modeling of this distribution suggests that between 2 < Av < 40 mag (or
roughly 1 < r < 0.1 pc) the material inside L977 is characterized by a density
profile n(r) \propto r^(-2). Direct measurement of the radial profile of a
portion of the cloud confirms this result. (more...)

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The categories of this paper are: ao-sci
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The categories of this paper are: patt-sol
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The categories of this paper are: cs
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The categories of this paper are: hep-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: cond-mat
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The categories of this paper are: quant-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: mtrl-th
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The categories of this paper are: econ
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The categories of this paper are: solv-int
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The categories of this paper are: hep-th
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The categories of this paper are: adap-org
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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The categories of this paper are: eess