Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A QSO plus host system lensed into a 6" Einstein ring by a low redshift
  galaxy   We report the serendipitous discovery of an "Einstein Ring" in the optical
band from the Sloan Digital Sky Survey (SDSS) data and associated four images
of a background source. The lens galaxy appears to be a nearby dwarf spheroid
at a redshift of 0.0375$\pm$0.002. The lensed quasar is at a redshift of
0.6842$\pm$0.0014 and its multiple images are distributed almost 360$^{o}$
around the lens nearly along a ring of radius $\sim$6."0. Single component lens
models require a mass of the galaxy of almost 10$^{12}$ M$_{\odot}$ within 6".0
from the lens center. With the available data we are unable to determine the
exact positions, orientations and fluxes of the quasar and the galaxy, though
there appears evidence for a double or multiple merging image of the quasar. We
have also detected strong radio and X-ray emissions from this system. It is
indicative that this ring system may be embedded in a group or cluster of
galaxies. This unique ring, by virtue of the closeness of the lens galaxy,
offers possible probe to some of the key issues like mass-to-light ratio of
intrinsically faint galaxies, existence of large scale magnetic fields in
elliptical galaxies etc.

2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn