* Astronomy

Title: The quasar-galaxy cross SDSS J1320+1644: A probable large-separation lensed quasar
Authors: Cristian E. Rusu, Masamune Oguri, Masanori Iye, Naohisa Inada, Issha Kayo, Min-Su Shin, Dominique Sluse, Michael A. Strauss

We report the discovery of a pair of quasars at z=1.487, with a separation of 8.585" ±0.002". 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 colours 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 ~ 4 x 10^{14}\ h_{70}^{-1}\ solar masses assuming an NFW model with a concentration parameter of c_{vir}=6, or a singular isothermal sphere profile with a velocity dispersion of ~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.

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