Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Near-infrared Integral Field Spectroscopy and Mid-infrared Spectroscopy
  of the Starburst Galaxy M82   We present new observations of the central regions of the starburst galaxy
M82 consisting of near-infrared H- and K-band integral field spectroscopy from
the MPE 3D instrument, and 2.4-45 micron spectroscopy from the Short Wavelength
Spectrometer (SWS) on board ISO. These measurements are used, together with
data from the literature, to re-examine the issue of extinction, determine the
physical conditions of the interstellar medium, and characterize the
composition of the stellar populations. We find that purely foreground
extinction cannot reproduce the global relative intensities of H recombination
lines from optical to radio wavelengths. A good fit is provided by a
homogeneous mixture of dust and sources, and with a visual extinction of 52
mag. The SWS data provide evidence for deviations from commonly assumed
extinction laws between 3 and 10 micron. The fine-structure lines of Ne, Ar,
and S detected with SWS imply an electron density of about 300 cm^{-3}, and
abundance ratios Ne/H and Ar/H nearly solar and S/H one-fourth solar. The
excitation of the ionized gas indicates an average temperature for the OB stars
of 37400 K, with little spatial variation. A random distribution of gas clouds
and ionizing clusters and an ionization parameter of about 10^{-2.3} represent
well the star-forming regions. From population synthesis and the
mass-to-K-light ratio, we conclude that the near-infrared continuum emission
across the starburst regions is dominated by red supergiants with average
temperatures ranging from 3600 K to 4500 K, and roughly solar metallicity. Our
data rule out significant contributions from older metal-rich giants in the
central few tens of parsecs of M82.

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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin
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The categories of this paper are: adap-org
18
The categories of this paper are: econ
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The categories of this paper are: q-bio
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The categories of this paper are: alg-geom
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The categories of this paper are: stat
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The categories of this paper are: comp-gas
2
The categories of this paper are: math
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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: gr-qc
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The categories of this paper are: hep-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex