Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Three QSOs acting as strong gravitational lenses   We report the discovery of three new cases of QSOs acting as strong
gravitational lenses on background emission line galaxies: SDSS J0827+5224
(zQSO = 0.293, zs = 0.412), SDSS J0919+2720 (zQSO = 0.209, zs = 0.558), SDSS
J1005+4016 (zQSO = 0.230, zs = 0.441). The selection was carried out using a
sample of 22,298 SDSS spectra displaying at least four emission lines at a
redshift beyond that of the foreground QSO. The lensing nature is confirmed
from Keck imaging and spectroscopy, as well as from HST/WFC3 imaging in the
F475W and F814W filters. Two of the QSOs have face-on spiral host galaxies and
the third is a QSO+galaxy pair. The velocity dispersion of the host galaxies,
inferred from simple lens modeling, is between \sigma_v = 210 and 285 km/s,
making these host galaxies comparable in mass with the SLACS sample of
early-type strong lenses.

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The categories of this paper are: solv-int
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
3
The categories of this paper are: physics
28
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: econ
15
The categories of this paper are: nucl-ex