Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: PS J1721+8842: A gravitationally lensed dual AGN system at redshift 2.37
  with two radio components   Dual-Active Galactic Nuclei (AGN) are a natural consequence of the
hierarchical structure formation scenario, and can provide an important test of
various models for black hole growth. However, due to their rarity and
difficulty to find at high redshift, very few confirmed dual-AGN are known at
the epoch where galaxy formation peaks. Here we report the discovery of a
gravitationally lensed dual-AGN system at redshift 2.37 comprising two
optical/IR quasars separated by 6.5+/-0.6 kpc, and a third compact (R_eff =
0.45+/-0.02 kpc) red galaxy that is offset from one of the quasars by 1.7+/-0.1
kpc. From Very Large Array imaging at 3 GHz, we detect 600 and 340 pc-scale
radio emission that is associated with both quasars. The 1.4 GHz luminosity
densities of the radio sources are about 10^24.35 W / Hz, which is consistent
with weak jets. However, the low brightness temperature of the emission is also
consistent with star-formation at the level of 850 to 1150 M_sun / yr. Although
this supports the scenario where the AGN and/or star-formation is being
triggered through an ongoing triple-merger, a post-merger scenario where two
black holes are recoiling is also possible, given that neither has a detected
host galaxy.

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The categories of this paper are: math
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The categories of this paper are: nlin
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The categories of this paper are: chem-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: q-alg
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-ex
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The categories of this paper are: q-bio
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The categories of this paper are: physics
31
The categories of this paper are: ao-sci
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The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph
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The categories of this paper are: math-ph
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The categories of this paper are: stat
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The categories of this paper are: solv-int
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The categories of this paper are: chao-dyn