Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Detailed Kinematic Map of Cassiopeia A's Optical Main Shell and Outer
  High-Velocity Ejecta   We present three-dimensional kinematic reconstructions of optically emitting
material in the young Galactic supernova remnant Cassiopeia A (Cas A). These
Doppler maps have the highest spectral and spatial resolutions of any previous
survey of Cas A and represent the most complete catalog of its optically
emitting material to date. We confirm that the bulk of Cas A's optically bright
ejecta populate a torus-like geometry tilted approximately 30 degrees with
respect to the plane of the sky with a -4000 to +6000 km/s radial velocity
asymmetry. Near-tangent viewing angle effects and an inhomogeneous surrounding
CSM/ISM environment suggest that this geometry and velocity asymmetry may not
be faithfully representative of the remnant's true 3D structure or the
kinematic properties of the original explosion. The majority of the optical
ejecta are arranged in several well-defined and nearly circular ring-like
structures with diameters between approximately 30 arcsec (0.5 pc) and 2 arcmin
(2 pc). These ejecta rings appear to be a common phenomenon of young
core-collapse remnants and may be associated with post-explosion input of
energy from plumes of radioactive 56Ni-rich ejecta that rise, expand, and
compress non-radioactive material. Our optical survey also encompassed Cas A's
faint outlying ejecta knots and exceptionally high-velocity NE and SW streams
of S-rich debris often referred to as `jets'. These outer knots, which exhibit
a chemical make-up suggestive of an origin deep within the progenitor star,
appear to be arranged in opposing and wide-angle outflows with opening
half-angles of approximately 40 degrees.

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The categories of this paper are: dg-ga
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The categories of this paper are: math
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The categories of this paper are: hep-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: physics
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-th
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The categories of this paper are: cs
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The categories of this paper are: plasm-ph
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The categories of this paper are: stat
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The categories of this paper are: cond-mat
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The categories of this paper are: eess
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The categories of this paper are: nucl-ex
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The categories of this paper are: math-ph