Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantitative optical and near-infrared spectroscopy of molecular
  hydrogen towards HH91A   Integral-field spectroscopy of molecular hydrogen in the optical wavelength
region and complementary long-slit near-infrared spectroscopy are presented
towards HH91A.The detection of some 200 H_2 lines arising from ro-vibrational
levels up to v'=8 ranging between 7700A and 2.3 microns is reported. The
emission arises from thermally excited gas where the bulk of the material is at
2750 K and where 1% is at 6000 K. The total column density of shocked gas is
N(H_2) = 10^{18} cm^{-2}. Non-thermal excitation scenarios such as
UV-fluorescence do not contribute to the excitation of H_2 towards HH91A. The
emission is explained in terms of a slow non-dissociative J-shock which
propagates into a low-density medium which has been swept-up by previous
episodes of outflows which have occurred in the evolved HH90/91 complex.

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The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
21
The categories of this paper are: adap-org