Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Kinematics of Intracluster Planetary Nebulae and the On-Going
  Subcluster Merger in the Coma Cluster Core   The Coma cluster is the richest and most compact of the nearby clusters, yet
there is growing evidence that its formation is still on-going. With a new
multi-slit imaging spectroscopy technique pioneered at the 8.2 m Subaru
telescope and FOCAS, we have detected and measured the line-of-sight velocities
of 37 intracluster planetary nebulae associated with the diffuse stellar
population of stars in the Coma cluster core, at 100 Mpc distance. We detect
clear velocity substructures within a 6 arcmin diameter field. A substructure
is present at ~5000 km/s, probably from in-fall of a galaxy group, while the
main intracluster stellar component is centered around ~6500 km/s, ~700 km/s
offset from the nearby cD galaxy NGC 4874. The kinematics and morphology of the
intracluster stars show that the cluster core is in a highly dynamically
evolving state. In combination with galaxy redshift and X-ray data this argues
strongly that the cluster is currently in the midst of a subcluster merger,
where the NGC 4874 subcluster core may still be self-bound, while the NGC 4889
subcluster core has probably dissolved. The NGC 4889 subcluster is likely to
have fallen into Coma from the eastern A2199 filament, in a direction nearly in
the plane of the sky, meeting the NGC 4874 subcluster arriving from the west.
The two inner subcluster cores are presently beyond their first and second
close passage, during which the elongated distribution of diffuse light has
been created. We predict the kinematic signature expected in this scenario, and
argue that the extended western X-ray arc recently discovered traces the arc
shock generated by the collision between the two subcluster gas halos. Any
preexisting cooling core region would have been heated by the subcluster
collision.

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The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
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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-th
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The categories of this paper are: hep-th
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The categories of this paper are: econ
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The categories of this paper are: nucl-ex
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The categories of this paper are: eess
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The categories of this paper are: funct-an
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The categories of this paper are: gr-qc
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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: math-ph
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The categories of this paper are: patt-sol