Reality or Mirage? Observational Test and Implications for the Claimed Extremely Magnified Quasar at $z=6.3$

Abstract

In the last two decades, approximately 200 quasars have been discovered at $z>6$, hosting active super-massive black holes with masses $M_{\bullet }\gtrsim 10^9{M}_{\odot }$. While these sources reflect only the tip of the iceberg of the black hole mass distribution, their detection challenges standard growth models. The most massive $z>6$ black hole that was inferred thus far (J0100+2802, $M_{\bullet }\approx 1.2\times 10^{10}{M}_{\odot }$) was recently claimed to be lensed, with a magnification factor $\mu =450$. Here, we perform a consistency check of this claim, finding that the detection of such source requires a bright-end slope $\beta \ge 3.7$ for the intrinsic quasar luminosity function, $\Phi (L)\propto L^{-\beta }$. Commonly used values of $\beta \sim 2.8$ are rejected at $>3\sigma$. If the claim is confirmed, it is very unlikely that all the remaining $51$ sources in the SDSS sample are not magnified. Furthermore, it suffices that $\gtrsim 25\%$ of the remaining sources are lensed for the intrinsic luminosity function to differ significantly (i.e., $>3\sigma$) from the observed one. The presence of additional extremely magnified sources in the sample would lower the requirement to $\sim 4\%$. Our results urge the community to perform more extended multi-wavelength searches targeting $z>6$ lensed quasars, also among known samples. This effort could vitally contribute to solving the open problem of the growth of the brightest $z\sim 7$ quasars.

arXiv commentPublished in ApJ: 8 pages, 4 figures. This is the final, published version

References in corpus (38)

• Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies
• A luminous quasar at a redshift of z = 7.085
• In the Beginning: The First Sources of Light and the Reionization of the Universe
• An 800-million-solar-mass black hole in a significantly neutral Universe at redshift 7.5
• Formation of the First Supermassive Black Holes
• Observational constraints on Cosmic Reionization
• A Survey of z>5.7 Quasars in the Sloan Digital Sky Survey II: Discovery of Three Additional Quasars at z>6
• An ultra-luminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30
• The Final SDSS High-Redshift Quasar Sample of 52 Quasars at z>5.7
• Updating quasar bolometric luminosity corrections
• What is the Highest Plausible Redshift of Luminous Quasars?
• Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). V. Quasar Luminosity Function and Contribution to Cosmic Reionization at z = 6
• Titans of the Early Universe: The Prato Statement on the Origin of the First Supermassive Black Holes
• Exploring Reionization-Era Quasars III: Discovery of 16 Quasars at $6.4\lesssim z\lesssim 6.9$ with DESI Legacy Imaging Surveys and UKIRT Hemisphere Survey and Quasar Luminosity Function at $z\sim 6.7$
• Galaxy luminosities, stellar masses, sizes, velocity dispersions as a function of morphological type
• Improved Dynamical Constraints on the Masses of the Central Black Holes in Nearby Low-mass Early-type Galactic Nuclei And the First Black Hole Determination for NGC 205
• The Opacity of the Intergalactic Medium Measured Along Quasar Sightlines at $z\sim 6$
• Quasar Strömgren Spheres Before Cosmological Reionization
• The Earliest Luminous Sources and the Damping Wing of the Gunn-Peterson Trough
• Frontier Fields: High-Redshift Predictions and Early Results
• Ionization near-zones associated with quasars at z ~ 6
• The Discovery of a Gravitationally Lensed Quasar at z = 6.51
• Correcting the z~8 Galaxy Luminosity Function for Gravitational Lensing Magnification Bias
• Black hole scaling relations of active and quiescent galaxies: Addressing selection effects and constraining virial factors
• A survey of luminous high-redshift quasars with SDSS and WISE II. the bright end of the quasar luminosity function at z ~ 5
• Constraining Reionization with the Evolution of the Luminosity Function of Lyman Alpha mitting Galaxies
• A distortion of very--high--redshift galaxy number counts by gravitational lensing
• Spatially Resolved Interstellar Medium and Highly-Excited Dense Molecular Gas in the Most Luminous Quasar at z=6.327
• Gravitational lenses magnify up to one third of the most distant quasars
• Gravitational Lensing of the SDSS High-Redshift Quasars
• A Snapshot Survey for Gravitational Lenses Among z>=4.0 Quasars: I. The z>5.7 Sample
• A Constraint on the Gravitational Lensing Magnification and Age of the Redshift z=6.28 Quasar SDSS 1030+0524
• Cosmic Reionization After Planck and Before JWST: An Analytic Approach
• Photon Trapping Enables Super-Eddington Growth of Black-Hole Seeds in Galaxies at High Redshift
• Constraining the Redshift z=6 Quasar Luminosity Function Using Gravitational Lensing
• Redshift evolution of the dynamical properties of massive galaxies from SDSS-III/BOSS
• Most Lensed Quasars at $z>6$ are Missed by Current Surveys
• Gravitational lensing magnification without multiple imaging

Cited by in corpus (9)

• EIGER III. JWST/NIRCam observations of the ultra-luminous high-redshift quasar J0100+2802
• Separating Accretion and Mergers in the Cosmic Growth of Black Holes with X-ray and Gravitational Wave Observations
• The space density of ultra-luminous QSOs at the end of reionization epoch by the QUBRICS Survey and the AGN contribution to the hydrogen ionizing background
• Constraining the Gravitational Lensing of $z\gtrsim 6$ Quasars from their Proximity Zones
• Truth or delusion? A possible gravitational lensing interpretation of the ultra-luminous quasar SDSS J010013.02+280225.8 at $z=6.30$
• Pure Density Evolution of the Ultraviolet Quasar Luminosity Function at $2\lesssim z\lesssim 6$
• The Infrared Medium-deep Survey. IX. Discovery of Two New $z\sim 6$ Quasars and Space Density down to $M_{1450}\sim -23.5$ mag
• Lensing in the Darkness: A Bayesian Analysis of 22 Chandra Sources at $z\gtrsim 6$ Shows No Evidence of Lensing
• X-Ray Evidence Against the Hypothesis that the Hyper-Luminous z=6.3 Quasar J0100+2802 is Lensed