Quasar Luminosity Function at z = 7

Abstract

We present the quasar luminosity function (LF) at $z=7$, measured with 35 spectroscopically confirmed quasars at $6.55<z<7.15$. The sample of 22 quasars from the Subaru High-$z$ Exploration of Low-Luminosity Quasars (SHELLQs) project, combined with 13 brighter quasars in the literature, covers an unprecedentedly wide range of rest-frame ultraviolet magnitudes over $-28<M_{1450}<-23$. We found that the binned LF flattens significantly toward the faint end populated by the SHELLQs quasars. A maximum likelihood fit to a double power-law model has a break magnitude $M_{1450}^{\ast }=-25.60_{-0.30}^{+0.40}$, a characteristic density ${\Phi }^{\ast }=1.35_{-0.30}^{+0.47}$ Gpc${}^{-3}$ mag${}^{-1}$, and a bright-end slope $\beta =-3.34_{-0.57}^{+0.49}$, when the faint-end slope is fixed to $\alpha =-1.2$ as observed at $z\le 6$. The overall LF shape remains remarkably similar from $z=4$ to $7$, while the amplitude decreases substantially toward higher redshifts, with a clear indication of an accelerating decline at $z\ge 6$. The estimated ionizing photon density, $10^{48.2\pm 0.1}$ s${}^{-1}$ Mpc${}^{-3}$, is less than 1 % of the critical rate to keep the intergalactic medium ionized at $z=7$, and thus indicates that quasars are not a major contributor to cosmic reionization.

The Astrophysical Journal Letters, in press

References in corpus (14)

• A luminous quasar at a redshift of z = 7.085
• The Hyper Suprime-Cam SSP Survey: Overview and Survey Design
• The Canada-France High-z Quasar Survey: nine new quasars and the luminosity function at redshift 6
• A Survey of z>5.7 Quasars in the Sloan Digital Sky Survey IV: Discovery of Seven Additional Quasars
• Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). V. Quasar Luminosity Function and Contribution to Cosmic Reionization at z = 6
• Subaru high-z exploration of low-luminosity quasars (SHELLQs). I. Discovery of 15 quasars and bright galaxies at 5.7 < z < 6.9
• A Survey of z~6 Quasars in the SDSS Deep Stripe: I. a Flux-Limited Sample at z_{AB}<21
• A Survey of z~6 Quasars in the SDSS Deep Stripe. II. Discovery of Six Quasars at z_{AB}>21
• Discovery of the First Low-Luminosity Quasar at z > 7
• Discovery of eight z ~ 6 quasars from Pan-STARRS1
• Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). II. Discovery of 32 Quasars and Luminous Galaxies at 5.7 < z < 6.8
• Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). IV. Discovery of 41 Quasars and Luminous Galaxies at 5.7 < z < 6.9
• Very high redshift quasars and the rapid emergence of super-massive black holes
• On the cosmic evolution of AGN obscuration and the X-ray luminosity function: XMM-Newton and Chandra spectral analysis of the 31.3 deg${}^2$ Stripe 82X

Cited by in corpus (24)

• Little Red Dots: Rapidly Growing Black Holes Reddened by Extended Dusty Flows
• "Little red dots" cannot reside in the same dark matter halos as comparably luminous unobscured quasars
• A blazar in the epoch of reionization
• Discovery of merging twin quasars at z = 6.05
• The SRG/eROSITA All-Sky Survey: X-ray beacons at late cosmic dawn
• SHELLQs. Bridging the Gap: JWST Unveils Obscured Quasars in the Most Luminous Galaxies at z > 6
• A Little Red Dot at $\mathbf{z}=7.3$ within a Large Galaxy Overdensity
• Constraining the AGN luminosity function from JWST with the X-ray Background
• AGN ruled out as the dominant source of cosmic reionization
• Prospects for Observing High-redshift Radio-loud Quasars in the SKA Era: Paving the Way for 21-cm Forest Observations
• Euclid preparation. Observational expectations for redshift z<7 active galactic nuclei in the Euclid Wide and Deep surveys
• Euclid: The potential of slitless infrared spectroscopy: A z=5.4 quasar and new ultracool dwarfs
• A weak Ly$\alpha$ halo for an extremely bright Little Red Dot: Indications of enshrouded SMBH growth
• JWST Discovery of a High-Redshift Tidal Disruption Event Candidate in COSMOS-Web
• The Ly$\alpha$ and Continuum Origins Survey. III. Investigating the Link between Galaxy Morphology, Merger Properties and LyC Escape
• Modelling LAEs in the Epoch of Reionization with OBELISK
• Shedding the envelope: JWST reveals a kiloparsec-scale [OIII]-weak Balmer shell around a z=7.64 quasar
• A first look at quasar-galaxy clustering at $z\simeq 7.3$
• Impact of anisotropic photon emission from sources during the epoch of reionisation
• Little Red Dots as Hidden Neutrino Sources
• Euclid: Discovery of 31 new quasars at $6.6<z<7.8$
• On the statistical characterization of the synchrotron multi-zone polarization of blazars
• Uncertainty-Aware Neural Networks for Fuzzy Dark Matter Model Selection from \texorpdfstring{$x_{\mathrm{HI}}$}{x_HI} Measurements
• Configuration Requirements for 21-cm Forest Background Quasar Searches with the Moon-based Interferometer