Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mid-Infrared Images of Luminous Infrared Galaxies in a Merging Sequence   We report mid-infrared observations of several luminous infrared galaxies
(LIGs) carried out with the Infrared Space Observatory. Our sample was chosen
to represent different phases of a merger sequence of galaxy-galaxy interaction
with special emphasis on early/intermediate stages of merging. The mid-infrared
emission of these LIGs shows extended structures for the early and intermediate
mergers, indicating that most of the mid-infrared luminosities are not from a
central active galactic nucleus (AGN). Both the infrared hardness (indicated by
the IRAS 12, 25, and 60 $\micron$ flux density ratios) and the peak-to-total
flux density ratios of these LIGs increase as projected separation of these
interacting galaxies become smaller, consistent with increasing star formation
activities that are concentrated to a smaller area as the merging process
advances. These observations provide among the first observational constraint
of largely theoretically based scenarios.

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The categories of this paper are: math
0
The categories of this paper are: hep-ph
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
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The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
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The categories of this paper are: eess
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The categories of this paper are: q-fin
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The categories of this paper are: acc-phys
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The categories of this paper are: adap-org
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The categories of this paper are: solv-int
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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: nlin
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The categories of this paper are: stat