Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: NICMOS Observations of Shocked H_2 in Orion   HST NICMOS narrowband images of the shocked molecular hydrogen emission in
OMC-1 are analyzed to reveal new information on the BN/KL outflow. The
outstanding morphological feature of this region is the array of molecular
hydrogen ``fingers'' emanating from the general vicinity of IRc2 and the
presence of several Herbig-Haro objects. The NICMOS images appear to resolve
individual shock fronts. This work is a more quantitative and detailed analysis
of our data from a previous paper (Schultz etal. 1999).
  Line strengths for the H_2 1--0 S(4) plus 2--1 S(6) lines at 1.89 micron are
estimated from measurements with the Paschen_alpha continuum filter F190N at
1.90 micron, and continuum measurements at 1.66 and 2.15 micron. We compare the
observed H_2 line strengths and ratios of the 1.89 micron and 2.12 micron 1--0
S(1) lines with models for molecular cloud shock waves. Most of the data cannot
be fit by J-shocks, but are well matched by C-shocks with shock velocities in
the range of 20--45 km/s and preshock densities of 10^{4} - 10^{6} cm^{-3},
similiar to values obtained in larger beam studies which averaged over many
shocks. There is also some evidence that shocks with higher densities have
lower velocities.

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The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin
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The categories of this paper are: funct-an
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The categories of this paper are: eess
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
1
The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: physics
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The categories of this paper are: hep-ex