Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Disks, Tori, and Cocoons: Emission and Absorption Diagnostics of AGN
  Environments   One of the most important problems in the study of active galaxies is
understanding the detailed geometry, physics, and evolution of the central
engines and their environments. The leading models involve an accretion disk
and torus structure around a central dense object, thought to be a supermassive
black hole. Gas found in the environment of AGN is associated with different
structures: molecular accretion disks, larger scale atomic tori, ionized and
neutral "cocoons" in which the nuclear regions can be embedded. All of them can
be studied at radio wavelengths by various means. Here, we summarize the work
that has been done to date in the radio band to characterize these structures.
Much has been learned about the central few parsecs of AGN in the last few
decades with contemporary instruments but the picture remains incomplete. In
order to be able to define a more accurate model of this region, significant
advances in sensitivity, spectral and angular resolution, and bandpass
stability are required. The necessary advances will only be provided by the
Square Kilometer Array and we discuss the possibilities that these dramatic
improvements will open for the study of the gas in the central region of AGN.

32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
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The categories of this paper are: cmp-lg
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The categories of this paper are: chao-dyn
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
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The categories of this paper are: solv-int
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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ