Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extended High-Ionization Nuclear Emission-Line Region in the Seyfert
  Galaxy NGC 4051   We present an optical spectroscopic analysis of the well-known Seyfert galaxy
NGC 4051. The high-ionization nuclear emission-line region (HINER) traced by
[Fe X]6374 is found to be spatially extended to a radius of 3a rcseconds (150
pc) west and southwest from the nucleus; NGC 4051 is the third example which
has an extended HINER.
  The nuclear spectrum shows that the flux of [Fe X]6374 is stronger than that
of [Fe VII] 6087 in our observation. This property cannot be interpreted in
terms of a simple one-zone photoionization model.
  In order to understand what happens in the nuclear region in NGC 4051, we
investigate the physical condition of the nuclear emission-line region in
detail using new photoionization models in which the following three
emission-line components are taken into account; (1) optically thick,
ionization-bounded clouds; (2) optically thin, matter-bounded clouds; and (3) a
contamination component which emits H$\alpha$ and H$\beta$ lines. Here the
observed extended HINER is considered to be associated with the low-density,
matter-bounded clouds. Candidates of the contamination component are either the
broad-line region (BLR) or nuclear star forming regions or both. The complexity
of the excitation condition found in NGC 4051 can be consistently understood if
we take account of these contamination components.

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The categories of this paper are: math-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-lat
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The categories of this paper are: q-alg
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The categories of this paper are: econ
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The categories of this paper are: acc-phys
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio
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The categories of this paper are: solv-int
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-th
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The categories of this paper are: supr-con
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The categories of this paper are: nlin
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The categories of this paper are: adap-org