The Discovery of a Gravitationally Lensed Quasar at z = 6.51

TL;DR

This paper reports the discovery of the first strongly lensed quasar at z=6.51, providing new insights into high-redshift quasars and gravitational lensing during the epoch of reionization.

Contribution

It presents the first detection of a strongly lensed quasar at z>6, revealing the potential for missed high-redshift quasars due to lensing effects.

Findings

Discovered a z=6.51 lensed quasar with multiple images.

Estimated magnification factor of ~50.

Suggests many high-redshift quasars may be undetected due to lensing contamination.

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 HST imaging reveals a multiple imaged system with a maximum image separation theta ~ 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.