The Discovery of a Gravitationally Lensed Quasar at z = 6.51

Xiaohui Fan, Feige Wang, Jinyi Yang, Charles R. Keeton, Minghao Yue, Ann Zabludoff, Fuyan Bian, Marco Bonaglia, Iskren Y. Georgiev, Joseph F. Hennawi, Jiangtao Li, Ian D. McGreer, Rohan Naidu, Fabio Pacucci, Sebastian Rabien, David Thompson, Bram Venemans, Fabian Walter, Ran Wang, Xue Bing Wu

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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.

Original languageEnglish (US)
Article numberL11
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Jan 10 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • gravitational lensing: strong
  • quasars: individual (J0439+1634)
  • quasars: supermassive black holes


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