Definitive upper bound on the negligible contribution of quasars to cosmic reionization

Abstract

Cosmic (hydrogen) reionization marks one of the major phase transitions of the universe at redshift z >= 6. During this epoch, hydrogen atoms in the intergalactic medium (IGM) were ionized by Lyman continuum (LyC) photons. However, it remains challenging to identify the major sources of the LyC photons responsible for reionization. In particular, individual contributions of quasars (or active galactic nuclei, AGNs) and galaxies are still under debate. Here we construct the far-ultraviolet (far-UV) luminosity function for type 1 quasars at z >= 6 that spans 10 magnitudes (-19 < M_UV < -29), conclusively showing that quasars made a negligible contribution to reionization. We mainly search for quasars in the low-luminosity range of M_UV > -23 mag that is critical to determine quasars' total LyC photon production but has been barely explored previously. We find that the quasar population can only provide less than 7% (95% confidence level) of the total photons needed to keep the universe ionized at z = 6.0 - 6.6. Our result suggests that galaxies, presumably low-luminosity star-forming systems, are the major sources of hydrogen reionization.

arXiv commentPublished in Nature Astronomy on June 16, 2022; 18 pages; authors' version; publisher's version is here (https://www.nature.com/articles/s41550-022-01708-w)

References in corpus (57)

• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey - The Hubble Space Telescope Observations, Imaging Data Products and Mosaics
• The Cosmic Evolution Survey (COSMOS) -- Overview
• The Great Observatories Origins Deep Survey: Initial Results From Optical and Near-Infrared Imaging
• UltraVISTA: a new ultra-deep near-infrared survey in COSMOS
• Radiative Transfer in a Clumpy Universe: III. The Nature of Cosmological Ionizing Sources
• The All-wavelength Extended Groth Strip International Survey (AEGIS) Data Sets
• The Chandra Deep Field-South Survey: 7 Ms Source Catalogs
• The Canada-France High-z Quasar Survey: nine new quasars and the luminosity function at redshift 6
• Reionization of the Inhomogeneous Universe
• GEMS: Galaxy Evolution from Morphologies and SEDs
• The Pan-STARRS1 distant z>5.6 quasar survey: more than 100 quasars within the first Gyr of the universe
• Third Data Release of the Hyper Suprime-Cam Subaru Strategic Program
• The VISTA Deep Extragalactic Observations (VIDEO) Survey
• Early star-forming galaxies and the reionization of the Universe
• The Final SDSS High-Redshift Quasar Sample of 52 Quasars at z>5.7
• Conditions for Reionizing the Universe with A Low Galaxy Ionizing Photon Escape Fraction
• The Bolometric Quasar Luminosity Function at z = 0-7
• Beyond the T Dwarfs: Theoretical Spectra, Colors, and Detectability of the Coolest Brown Dwarfs
• A Cosmic Variance Cookbook
• The SPHINX Cosmological Simulations of the First Billion Years: the Impact of Binary Stars on Reionization
• The first ultraviolet quasar stacked spectrum at z=2.4 from WFC3
• Keck Spectroscopy of Faint 3<z<7 Lyman Break Galaxies:- II. A High Fraction of Line Emitters at Redshift Six
• Four quasars above redshift 6 discovered by the Canada-France High-z Quasar Survey
• Evolution of the AGN UV luminosity function from redshift 7.5
• Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). V. Quasar Luminosity Function and Contribution to Cosmic Reionization at z = 6
• Gemini GNIRS near-infrared spectroscopy of 50 quasars at z>~5.7
• Spectroscopic Observations of Lyman-Break Galaxies at Redshift ~ 4, 5 and 6 in the GOODS-South Field
• No evidence for a significant AGN contribution to cosmic hydrogen reionization
• The mean free path of ionizing photons at 5 < z < 6: evidence for rapid evolution near reionization
• Gas Clumping in Self-Consistent Reionisation Models
• CANDELSz7: a large spectroscopic survey of CANDELS galaxies in the reionization epoch
• Six more quasars at redshift 6 discovered by the Canada-France High-z Quasar Survey
• Physical Properties of Spectroscopically-Confirmed Galaxies at z >= 6. II. Morphology of the Rest-Frame UV Continuum and Lyman-alpha Emission
• The Obelisk simulation: galaxies contribute more than AGN to HI reionization of protoclusters
• The Lyman Continuum escape fraction of faint galaxies at z~3.3 in the CANDELS/GOODS-North, EGS, and COSMOS fields with LBC
• Relative Role of Stars and Quasars in Cosmic Reionization
• Semi-analytic forecasts for JWST -- IV. Implications for cosmic reionization and LyC escape fraction
• The Spectral Slope and Escape Fraction of Bright Quasars at $z\sim 3.8$: the Contribution to the Cosmic UV Background
• Minor Contribution of Quasars to Ionizing Photon Budget at z~6: Update on Quasar Luminosity Function at the Faint-end with Subaru/Suprime-Cam
• No strong dependence of Lyman continuum leakage on physical properties of star-forming galaxies at $3.1\lesssim \mathbf{z}\lesssim 3.5$
• Near-Infrared Imaging of a z=6.42 Quasar Host Galaxy With the Hubble Space Telescope Wide Field Camera 3
• The Magellan M2FS Spectroscopic Survey of High-$z$ Galaxies: Lyα Emitters at $z\approx 6.6$ and the Evolution of Lyα Luminosity Function over $z\approx 5.7-6.6$
• Discovery of A Faint Quasar at z~6 and Implications for Cosmic Reionization
• The Predicament of Absorption-Dominated Reionization: Increased Demands on Ionizing Sources
• Cosmic variance of $z>7$ galaxies: Prediction from BlueTides
• A high space density of L* Active Galactic Nuclei at z~4 in the COSMOS field
• 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
• The host galaxies of z=7 quasars: predictions from the BlueTides simulation
• A Magellan M2FS Spectroscopic Survey of Galaxies at 5.5<z<6.8: Program Overview and a Sample of the Brightest Lyman-alpha Emitters
• The Magellan M2FS Spectroscopic Survey of High-Redshift Galaxies: A Sample of 260 Ly$\alpha$ Emitters at Redshift $z\approx 5.7$
• High-redshift quasars and their host galaxies II: multiphase gas and stellar kinematics
• Keck Spectroscopy of Lyman-break Galaxies and its Implications for the UV-continuum and Ly_alpha Luminosity Functions at z>6
• Early galaxy formation and its large-scale effects
• Ionizing radiation from AGNs at z>3.3 with the Subaru Hyper Suprime-Cam Survey and the CFHT Large Area U-band Deep Survey (CLAUDS)
• A Physical Model for the Quasar Luminosity Function Evolution between Cosmic Dawn and High Noon
• The Contribution of AGN Accretion Disks to Hydrogen Reionization

Cited by in corpus (16)

• A Candidate of a Least-Massive Black Hole at the First 1.1 Billion Years of the Universe
• Peering into cosmic reionization: the Ly$\alpha$ visibility evolution from galaxies at $z$ = 4.5-8.5 with JWST
• The Pan-STARRS1 $\mathbf{z}>5.6$ Quasar Survey: III. The $\mathbf{z}\approx 6$ Quasar Luminosity Function
• An Hα Impression of Lyα Galaxies at $z\simeq 6$ with Deep JWST/NIRCam Imaging
• Metal enrichment and evolution in four z > 6.5 quasar sightlines observed with JWST/NIRSpec
• A universal average spectral energy distribution for quasars from optical to extreme ultraviolet
• The THESAN project: connecting ionized bubble sizes to their local environments during the Epoch of Reionization
• The Assembly of Black Hole Mass and Luminosity Functions of High-redshift Quasars via Multiple Accretion Episodes
• Ionizing photon production and escape fractions during cosmic reionization in the TNG50 simulation
• Evolution of the Lyman-α emitting fraction and UV properties of lensed star-forming galaxies between 2.9 < z < 6.7
• AGN ruled out as the dominant source of cosmic reionization
• Galaxy Formation and Symbiotic Evolution with the Inter-Galactic Medium in the Age of ELT-ANDES
• 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
• The Composite Spectral Energy Distribution of Quasars is Surprisingly Universal Since Cosmic Noon
• Impact of the turnover in the high-z galaxy luminosity function on the 21-cm signal during Cosmic Dawn and Epoch of Reionization
• POLAR-II: modeling star formation history of galaxies on the 21-cm signal from Epoch of Reionization