Unresolved X-ray background: clues on galactic nuclear activity at z>6

Abstract

We study, by means of dedicated simulations of massive black hole build-up, the possibility to constraint the existence and nature of the AGN population at z>6 with available and planned X-ray and near infrared space telescopes. We find that X-ray deep-field observations can set important constraints to the faint-end of the AGN luminosity function at very high redshift. Planned X-ray telescopes should be able to detect AGN hosting black holes with masses down to >10^5 Msun (i.e., X-ray luminosities in excess of 10^42 erg s^-1), and can constrain the evolution of the population of massive black hole at early times (6<z<10). We find that this population of AGN should contribute substantially (~25%) to the unresolved fraction of the cosmic X-ray background in the 0.5-10 keV range, and that a significant fraction (~3-4%) of the total background intensity would remain unaccounted even after future X-ray observations. As byproduct, we compute the expected UV background from AGN at z>6 and we discuss the possible role of AGN in the reionization of the Universe at these early epochs, showing that AGN alone can provide enough ionizing photons only in the (improbable) case of an almost completely homogeneous inter-galactic medium. Finally, we show that super-Eddington accretion, suggested by the observed QSOs at z>6, must be a very rare event, confined to black holes living in the highest density peaks.

9 pages, 7 figures, MNRAS in press

References in corpus (37)

• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters
• Radiative Transfer in a Clumpy Universe: II. The Utraviolet Extragalactic Background
• Local Supermassive Black Holes, Relics of Active Galactic Nuclei and the X-ray Background
• The Assembly and Merging History of Supermassive Black Holes in Hierarchical Models of Galaxy Formation
• Massive Black Holes as Population III Remnants
• A Survey of z>5.8 Quasars in the Sloan Digital Sky Survey I: Discovery of Three New Quasars and the Spatial Density of Luminous Quasars at z~6
• The Hubble Ultra Deep Field
• Formation of Supermassive Black Holes by Direct Collapse in Pregalactic Halos
• Formation of the First Supermassive Black Holes
• The Chandra Deep Field-North Survey. XIII. 2 Ms Point-Source Catalogs
• The X-ray-to-Optical Properties of Optically-Selected Active Galaxies Over Wide Luminosity and Redshift Ranges
• Pair-Instability Supernovae, Gravity Waves, and Gamma-Ray Transients
• Collapse of Primordial Gas Clouds and the Formation of Quasar Black Holes
• Absolute measurement of the unresolved cosmic X-ray background in the 0.5-8 keV band with Chandra
• The resolved fraction of the Cosmic X-ray Background
• Rapid growth of high redshift black holes
• Black Hole Spin Evolution
• Optical and Infrared Properties of the 2 Ms Chandra Deep Field-North X-ray Sources
• Massive black hole seeds from low angular momentum material
• The Fall of AGN and the Rise of Star-Forming Galaxies: A Close Look at the Chandra Deep Field X-ray Number Counts
• Quasars: the characteristic spectrum and the induced radiative heating
• Spin, Accretion and the Cosmological Growth of Supermassive Black Holes
• Quasars at z=6: the survival of the fittest
• The Chandra Deep Field North Survey. VI. The Nature of the Optically Faint X-ray Source Population
• Quasar Luminosity Functions from Joint Evolution of Black Holes and Host Galaxies
• Origin of Quasar Progenitors from the Collapse of Low-Spin Cosmological Perturbations
• A Limit from the X-ray Background on the Contribution of Quasars to Reionization
• Constraints from Gravitational Recoil on the Growth of Supermassive Black Holes at High Redshift
• The Imprint of the Cosmic Dark Ages on the Near Infrared Background
• The High-Redshift He II Gunn-Peterson Effect: Implications and Future Prospects
• Formation of the Black Holes in the Highest Redshift Quasars
• Very High Redshift X-ray Selected AGN in the Chandra Deep Field-North
• A Possible New Population of Sources with Extreme X-Ray / Optical Ratios
• Faint Source Counts from Off-source Fluctuation Analysis on Chandra Observations of the Hubble Deep Field-North
• The Chandra Deep Field South/GOODS survey. Optically faint X-ray sources
• Cosmic Backgrounds from Miniquasars
• Where are the sources of the Near Infrared Background?

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• A Survey of z~6 Quasars in the SDSS Deep Stripe: I. a Flux-Limited Sample at z_{AB}<21
• The GMRT-EoR Experiment: A new upper limit on the neutral hydrogen power spectrum at z~8.6
• Constraints on X-ray Emissions from the Reionization Era
• Radiative Feedback from high mass X-ray binaries on the formation of the first galaxies and early reionization
• How realistic UV spectra and X-rays suppress the abundance of direct collapse black holes
• Relative Role of Stars and Quasars in Cosmic Reionization
• Understanding black hole mass assembly via accretion and mergers at late times in cosmological simulations
• Assessing the redshift evolution of massive black holes and their hosts
• Constraining the dark energy equation of state using LISA observations of spinning Massive Black Hole binaries
• The role of relativistic jets in the heaviest and most active supermassive black holes at high redshift
• The Chandra Deep Fields: Lifting the Veil on Distant Active Galactic Nuclei and X-Ray Emitting Galaxies
• Limits on the high redshift growth of massive black holes
• Spectrum of the unresolved cosmic X ray background: what is unresolved 50 years after its discovery
• Exploring 21cm - Lyman Alpha emitter synergies for SKA
• Lyalpha versus X-ray heating in the high-z IGM
• High redshift AGNs and HI reionisation: limits from the unresolved X-ray background
• The Concerted Impact of Galaxies and QSOs on the Ionization and Thermal State of the Intergalactic Medium
• Radiation from early black holes - I: effects on the neutral inter-galactic medium
• X-ray background and its correlation with the 21 cm signal
• Heating and Ionization of the Primordial Intergalactic Medium by High Mass X-ray Binaries
• A practical guide to the massive black hole cosmic history
• Detecting quasars at very high redshift with next generation X-ray telescopes
• Evolution of massive black holes
• A Search for X-Ray Reionization Signatures from Cross-Correlation of Wmap and ROSAT Rass Data