Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 2MASS wide field extinction maps - I. The Pipe nebula   We present a 8 deg x 6 deg, high resolution extinction map of the Pipe nebula
using 4.5 million stars from the Two Micron All Sky Survey (2MASS) point source
catalog. The use of NICER, a robust and optimal technique to map the dust
column density, allows us to detect a Av = 0.5 mag extinction at a 3-sigma
level with a 1 arcmin resolution. We find for the Pipe nebula a normal
reddening law, E(J-H) = (1.85 +/- 0.15) E(H-K). We measure the cloud distance
using Hipparchos and Tycho parallaxes, and obtain ~130 pc. This, together with
the total estimated mass, 10^4 Msun, makes the Pipe the closest massive cloud
complex to Earth. We compare the NICER extinction map to the NANTEN 12CO
observations and derive with unprecedented accuracy the relationship between
the near-infrared extinction and the 12CO column density and hence (indirectly)
the 12CO X-factor, that we estimate to be 2.91 10^20 cm^-2 K^-1 km^-1 s in the
range Av <- [0.9, 5.4] mag. We identify ~1500 OH/IR stars located within the
Galactic bulge in the direction of the Pipe field. This represents a
significant increase of the known numbers of such stars in the Galaxy. Our
analysis confirms the power and simplicity of the color excess technique to
study molecular clouds. The comparison with the NANTEN 12CO data corroborates
the insensitivity of CO observations to low column densities (up to
approximately 2 mag in Av), and shows also an irreducible uncertainty in the
dust-CO correlation of about 1 mag of visual extinction.

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The categories of this paper are: bayes-an
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The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
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The categories of this paper are: plasm-ph
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The categories of this paper are: stat
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The categories of this paper are: dg-ga
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The categories of this paper are: nlin
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The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
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The categories of this paper are: econ
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The categories of this paper are: hep-ex
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The categories of this paper are: supr-con
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The categories of this paper are: comp-gas