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.

报道了发现了一种在再电离时期检测到的强引力透镜下的 lensed quasar，它是迄今为止已知的 z > 5 最亮的类星体，并表明以前的调查可能错过了大量的强引力透镜下的高红移类星体。

发现一个红移为 6.51 的引力透镜类星体

The Discovery of a Gravitationally Lensed Quasar at z = 6.51

Quasars are galaxies hosting accreting supermassive black holes; due to their
brightness, they are unique probes of the early universe. To date, only few
quasars have been reported at $z > 6.5$ ($<$800 Myr after the Big Bang). In
this work, we present six additional $z \gtrsim 6.5$ quasars discovered using
the Pan-STARRS1 survey. We use a sample of 15 $z \gtrsim 6.5$ quasars to
perform a homogeneous and comprehensive analysis of this highest-redshift
quasar population. We report four main results: (1) the majority of
$z\gtrsim$6.5 quasars show large blueshifts of the broad CIV
1549\AA$\,$emission line compared to the systemic redshift of the quasars, with
a median value $\sim$3$\times$ higher than a quasar sample at $z\sim$1; (2) we
estimate the quasars' black hole masses (M$\rm_{BH}\sim$0.3$-$5 $\times$
10$^{9}$ M$_{\odot}$) via modeling of the MgII 2798\AA$\,$emission line and
rest-frame UV continuum; we find that quasars at high redshift accrete their
material (with $\langle (L_{\mathrm{bol}}/L_{\mathrm{Edd}}) \rangle = 0.39$) at
a rate comparable to a luminosity-matched sample at lower$-$redshift, albeit
with significant scatter ($0.4$ dex); (3) we recover no evolution of the
FeII/MgII abundance ratio with cosmic time; (4) we derive near zone sizes;
together with measurements for $z\sim6$ quasars from recent work, we confirm a
shallow evolution of the decreasing quasar near zone sizes with redshift.
Finally, we present new millimeter observations of the [CII] 158 $\mu$m
emission line and underlying dust continuum from NOEMA for four quasars, and
provide new accurate redshifts and [CII]/infrared luminosities estimates. The
analysis presented here shows the large range of properties of the most distant
quasars.

该研究报告从高红移的量子星系谈起，围绕发现和研究这个最遥远的天体的特性进行了广泛和全面的分析，并提供了精确的红移测量和 [CII]/ 红外区亮度估计的新的毫米波观测结果。