The Discovery of a Gravitationally Lensed Quasar at z = 6.51

Abstract

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.