Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Multi-wavelength Probes of Obscuration Towards the Narrow Line Region in
  Seyfert Galaxies   We present a study of reddening and absorption towards the Narrow Line
Regions (NLR) in active galactic nuclei (AGN) selected from the Revised
Shapley-Ames, 12mu, and Swift/Burst Alert Telescope samples. For the sources in
host galaxies with inclinations of b/a > 0.5, we find that mean ratio of [O
III] 5007A, from ground-based observations, and [O IV] 28.59mu, from
Spitzer/Infrared Spectrograph observations, is a factor of 2 lower in Seyfert
2s than Seyfert 1s. The combination of low [O III]/[O IV] and [O III] 4363/5007
ratios in Seyfert 2s suggests more extinction of emission from the NLR than in
Seyfert 1s. Similar column densities of dusty gas, NH ~ several X 10^21 cm^-2,
can account for the suppression of both [O III] 5007A and [O III] 4363A, as
compared to those observed in Seyfert 1s. Also, we find that the X-ray line
OVII 22.1A is weaker in Seyfert 2s, consistent with absorption by the same gas
that reddens the optical emission. Using a Hubble Space Telescope/Space
Telescope Imaging Spectrograph slitless spectrum of the Seyfert 1 galaxy NGC
4151, we estimate that only ~ 30% of the [O III] 5007A comes from within 30 pc
of the central source, which is insufficient to account for the low [O
III]/[OIV] ratios in Seyfert 2s. If Seyfert 2 galaxies have similar intrinsic
[OIII] spatial profiles, the external dusty gas must extend further out along
the NLR, perhaps in the form of nuclear dust spirals that have been associated
with fueling flows towards the AGN.

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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: stat
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The categories of this paper are: atom-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-th
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The categories of this paper are: comp-gas
1
The categories of this paper are: cs
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The categories of this paper are: ao-sci
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The categories of this paper are: econ
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The categories of this paper are: nlin
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The categories of this paper are: adap-org
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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin