Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: ISOCAM view of the starburst galaxies M82, NGC253, and NGC1808   We present results of mid-infrared 5.0-16.5 micron spectrophotometric imaging
of the starburst galaxies M82, NGC253, and NGC1808 from the ISOCAM instrument
on board the Infrared Space Observatory. The mid-infrared spectra of the three
galaxies are very similar in terms of features present. The > 11 micron
continuum attributed to very small dust grains (VSGs) exhibits a large spread
in intensity relative to the short-wavelength emission. We find that the 15
micron dust continuum flux density correlates well with the fine-structure
[ArII] 6.99 micron line flux and thus provides a good quantitative indicator of
the level of star formation activity. By contrast, the 5-11 micron region
dominated by emission from polycyclic aromatic hydrocarbons (PAHs) has a nearly
invariant shape. Variations in the relative intensities of the PAH features are
nevertheless observed, at the 20%-100% level. We illustrate extinction effects
on the shape of the mid-infrared spectrum of obscured starbursts, emphasizing
the differences depending on the applicable extinction law and the consequences
for the interpretation of PAH ratios and extinction estimates. The relative
spatial distributions of the PAH, VSG, and [ArII] 6.99 micron emission between
the three galaxies exhibit remarkable differences. The < 1 kpc size of the
mid-infrared source is much smaller than the optical extent of our sample
galaxies and 70%-100% of the IRAS 12 micron flux is recovered within the ISOCAM
< 1.5 arcmin squared field of view, indicating that the nuclear starburst
dominates the total mid-infrared emission while diffuse light from quiescent
disk star formation contributes little.

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The categories of this paper are: hep-lat
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The categories of this paper are: quant-ph
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The categories of this paper are: nlin
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The categories of this paper are: cs
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: econ
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The categories of this paper are: adap-org
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The categories of this paper are: cmp-lg
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The categories of this paper are: gr-qc
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The categories of this paper are: stat
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: eess
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The categories of this paper are: ao-sci