The Discovery of a Gravitationally Lensed Quasar at z = 6.51
Hennawi, Joseph F.; Fan, Xiaohui; McGreer, Ian D.; Keeton, Charles R.; Walter, Fabian; Bian, Fuyan; Georgiev, Iskren Y.; Zabludoff, Ann; Yang, Jinyi; Wang, Feige; Venemans, Bram; Yue, Minghao; Rabien, Sebastian; Li, Jiangtao; Wang, Ran; Wu, Xue-Bing; Pacucci, Fabio; Thompson, David; Bonaglia, Marco; Naidu, Rohan
United States, Chile, Italy, Germany, China
Abstract
Strong gravitational lensing provides a powerful probe of the physical properties of quasars and their host galaxies. A high fraction of the most luminous high-redshift quasars was predicted to be lensed due to magnification bias. However, no multiple imaged quasar was found at z > 5 in previous surveys. We report the discovery of J043947.08+163415.7, a strongly lensed quasar at z = 6.51, the first such object detected at the epoch of reionization, and the brightest quasar yet known at z > 5. High-resolution Hubble Space Telescope imaging reveals a multiple imaged system with a maximum image separation θ ∼ 0.″2, best explained by a model of three quasar images lensed by a low-luminosity galaxy at z ∼ 0.7, with a magnification factor of ∼50. The existence of this source suggests that a significant population of strongly lensed, high-redshift quasars could have been missed by previous surveys, as standard color selection techniques would fail when the quasar color is contaminated by the lensing galaxy.