Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Large Scale CO and [CI] emission in the rho Ophiuchi Molecular Cloud   We present a comprehensive study of the rho Ophiuchi molecular cloud that
addresses aspects of the physical structure and condition of the molecular
cloud and its photodissociation region (PDR) by combining far-infrared and
submillimeter-wave observations with a wide range of angular scale and
resolution. We present 40'x40' maps in CO(4-3) and [CI](3P1-3P0) line emission
from the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO), and
pointed observations in the CO(7-6) and [CI](3P2-3P1) lines. Within, smaller
spectral line maps of the cloud in CO, CS, HCO+ and their rare isotopomers are
made at the Heinrich Hertz Submillimeter Telescope Observatory (HHT) in
Arizona. Comparison with far-infrared and submillimeter continuum emission, and
near-infrared H2 emission allows clearer determination of the physical and
chemical structure of the rho Oph photodissociation region (PDR). The
excitation conditions needed to produce the observed HCO+ and [OI] emission
directly imply inhomogeneous structure. Strong chemical gradients are observed
in HCO+ and CS; the former is ascribed to a local enhancement in the H2
ionization rate, the latter is principally due to shocks. The distribution of
[CI] is very similar to C18O, and generally consistent with illumination from
the 'far' side of the cloud. A notable exception is found at the the western
edge of the cloud, where UV photons create a PDR viewed `edge-on'. The
abundance of atomic carbon is accurately modeled using a radiation field that
decreases with increasing projected distance from the exciting star HD147889.
In contrast to conclusions of other studies, we find that no non-equilibrium
chemistry is needed to enhance the atomic carbon abundance.

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The categories of this paper are: q-fin
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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: cond-mat
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The categories of this paper are: q-alg
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The categories of this paper are: econ
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The categories of this paper are: patt-sol
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The categories of this paper are: gr-qc
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The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: funct-an
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The categories of this paper are: dg-ga
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The categories of this paper are: comp-gas
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The categories of this paper are: acc-phys