The quasar-galaxy cross SDSS J1320+1644: A probable large-separation
  lensed quasar
  We report the discovery of a pair of quasars at $z=1.487$, with a separation
of $8\farcs585\pm0\farcs002$. Subaru Telescope infrared imaging reveals the
presence of an elliptical and a disk-like galaxy located almost symmetrically
between the quasars, creating a cross-like configuration. Based on absorption
lines in the quasar spectra and the colors of the galaxies, we estimate that
both galaxies are located at redshift $z=0.899$. This, as well as the
similarity of the quasar spectra, suggests that the system is a single quasar
multiply imaged by a galaxy group or cluster acting as a gravitational lens,
although the possibility of a binary quasar cannot be fully excluded. We show
that the gravitational lensing hypothesis implies these galaxies are not
isolated, but must be embedded in a dark matter halo of virial mass $\sim 4
\times 10^{14}\ h_{70}^{-1}\ {M}_\odot$ assuming an NFW model with a
concentration parameter of $c_{vir}=6$, or a singular isothermal sphere profile
with a velocity dispersion of $\sim 670$ km s$^{-1}$. We place constraints on
the location of the dark matter halo, as well as the velocity dispersions of
the galaxies. In addition, we discuss the influence of differential reddening,
microlensing and intrinsic variability on the quasar spectra and broadband
photometry.
