Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: SDSS J1029+2623: A Gravitationally Lensed Quasar with an Image
  Separation of 22.5 Arcseconds   We report the discovery of a cluster-scale lensed quasar, SDSS J1029+2623,
selected from the Sloan Digital Sky Survey. The lens system exhibits two lensed
images of a quasar at z_s=2.197. The image separation of 22.5" makes it the
largest separation lensed quasar discovered to date. The similarity of the
optical spectra and the radio loudnesses of the two components support the
lensing hypothesis. Images of the field show a cluster of galaxies at z_l~0.55
that is responsible for the large image separation. The lensed images and the
cluster light center are not collinear, which implies that the lensing cluster
has a complex structure.

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The categories of this paper are: hep-ph
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: ao-sci
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The categories of this paper are: stat
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The categories of this paper are: eess
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The categories of this paper are: q-alg
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The categories of this paper are: cond-mat
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
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The categories of this paper are: atom-ph
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The categories of this paper are: math