SDSS J2222+2745: A Gravitationally Lensed Sextuple Quasar With a Maximum Image Separation of 15.″1 Discovered in the Sloan Giant Arcs Survey

Abstract

We report the discovery of a unique gravitational lens system, SDSS J2222+2745, producing five spectroscopically confirmed images of a z s = 2.82 quasar lensed by a foreground galaxy cluster at z l = 0.49. We also present photometric and spectroscopic evidence for a sixth lensed image of the same quasar. The maximum separation between the quasar images is 15. 1. Both the large image separations and the high image multiplicity of the lensed quasar are in themselves rare, and observing the combination of these two factors is an exceptionally unlikely occurrence in present datasets. This is only the third known case of a quasar lensed by a cluster, and the only one with six images. The lens system was discovered in the course of the Sloan Giant Arcs Survey, in which we identify candidate lenses in the Sloan Digital Sky Survey and target these for follow up and verification with the 2.56m Nordic Optical Telescope. Multi-band photometry obtained over multiple epochs from September 2011 to September 2012 reveals significant variability at the ∼ 10 − 30% level in some of the quasar images, indicating that measurements of the relative time delay between quasar images will be feasible. In this lens system we also identify a bright (g = 21.5) giant arc corresponding to a strongly lensed background galaxy at z s = 2.30. We fit parametric models of the lens system, constrained by the redshift and positions of the quasar images and the redshift and position of the giant arc. The predicted time delays between different pairs of quasar images range from ∼ 100 days to ∼ 6 years.

A Keck Adaptive Optics Survey of a Representative Sample of Gravitationally Lensed Star-Forming Galaxies: High Spatial Resolution Studies of Kinematics and Metallicity Gradients

“…In some cases, e.g., CSWA159, mass models were already available in the literature (Dahle et al 2013). Depending on the circumstances, three distinct methods were used in constructing new mass models as detailed below.…”

“…Multiple images are then identified from their similar colors and/or spectroscopic redshifts, if available, in conjunction with a preliminary guess for the mass model. In many cases, spectroscopic redshifts are available in the literature (Dahle et al 2013;Stark et al 2013;Brewer et al 2011) and from our OSIRIS observations. In a few cases where redshifts are not available for identified multiple images, we leave the redshift as a free parameter.…”

Spatially Resolved Patchy Lyα Emission within the Central Kiloparsec of a Strongly Lensed Quasar Host Galaxy at z = 2.8

“…Previous papers described the discovery and initial follow-up (Dahle et al 2013), time delay measurements of the three brightest quasar images (Dahle et al 2015), and detailed strong lens modeling (Sharon et al 2017) of SDSSJ2222+2745. Here, we build on previous studies of this source using the lens model from Sharon et al (2017).…”

“…The large separation minimizes the confounding effects of the foreground lens light, and these systems also tend to have high magnifications over a larger area in the source plane, such that the host galaxy is highly magnified out to physical projected radii of several kiloparsecs. Currently, there are only three large separation lensed quasars known: SDSSJ1004 +4112 (Inada et al 2003;Oguri et al 2004;Sharon et al 2005;Fian et al 2016), SDSSJ1029+2623 (Inada et al 2006;Oguri et al 2008Oguri et al , 2013, and SDSSJ2222+2745 (Dahle et al 2013(Dahle et al , 2015Sharon et al 2017). While strong-lensing studies of these systems using HST can provide uniquely high spatial resolution, the technique has been relatively underutilized.…”

Lens Model and Time Delay Predictions for the Sextuply Lensed Quasar SDSS J2222+2745*

“…Lensing configurations that involve a quasar lensed by a single massive galaxy are more common; however, the lensing magnification of a single galaxy is typically significantly lower than in the Galaxy cluster case. Unique to the cluster-lensed quasar configurations, the multiple images of the lensed quasar have large separations (14 6-22 5; Inada et al 2003Inada et al , 2006Dahle et al 2013) and high magnifications; the lensed active nucleus is point-like, providing accurate positional constraints, and is variableenabling measurements of the time delay between images of the same source. The high tangential magnification stretches the host galaxy of the quasar into a giant arc, thus resolving it from the light of the active nucleus, which usually dominates in a high-redshift quasar.…”