The X-ray properties of z$\sim$6 luminous quasars

Abstract

We present a systematic analysis of X-ray archival data of all the 29 quasars (QSOs) at $z$ > 5.5 observed so far with Chandra, XMM-Newton and Swift-XRT, including the most-distant quasar ever discovered, ULAS J1120+0641 ($z$ = 7.08). This study allows us to place constraints on the mean spectral properties of the primordial population of luminous Type 1 (unobscured) quasars. Eighteen quasars are detected in the X-ray band, and we provide spectral-fitting results for their X-ray properties, while for the others we provide upper limits to their soft (0.5-2.0 keV) X-ray flux. We measured the power-law photon index and derived an upper limit to the column density for the five quasars (J1306+0356, J0100+2802, J1030+0524, J1148+5251, J1120+0641) with the best spectra (> 30 net counts in the 0.5-7.0 keV energy range) and find that they are consistent with values from the literature and lower-redshift quasars. By stacking the spectra of ten quasars detected by Chandra in the redshift range 5.7 $\le$ $z$ $\le$ 6.1 we find a mean X-ray power-law photon index of $\Gamma =1.92_{-0.27}^{+0.28}$ and a neutral intrinsic absorption column density of $N_H\le 10^{23}$ cm${}^{-2}$. These results suggest that the X-ray spectral properties of luminous quasars have not evolved up to $z$ $\approx$ 6. We also derived the optical-X-ray spectral slopes (${\alpha }_{ox}$) of our sample and combined them with those of previous works, confirming that ${\alpha }_{ox}$ strongly correlates with UV monochromatic luminosity at 2500 Å. These results strengthen the non-evolutionary scenario for the spectral properties of luminous active galactic nuclei (AGN).

12 pages, 7 figures, accepted for publication in Astronomy and Astrophysics

References in corpus (23)

• A luminous quasar at a redshift of z = 7.085
• The X-ray-to-Optical Properties of Optically-Selected Active Galaxies Over Wide Luminosity and Redshift Ranges
• The Chandra Deep Field-South Survey: 7 Ms Source Catalogs
• The X-ray Properties of the Most-Luminous Quasars from the Sloan Digital Sky Survey
• The Pan-STARRS1 distant z>5.6 quasar survey: more than 100 quasars within the first Gyr of the universe
• The evolution of massive black hole seeds
• The Hard X-ray Spectrum as a Probe for Black-Hole Growth in Radio-Quiet Active Galactic Nuclei
• Super-Critical Growth of Massive Black Holes from Stellar-Mass Seeds
• X-ray Insights into the Nature of PHL 1811 Analogs and Weak Emission-Line Quasars: Unification with a Geometrically Thick Accretion Disk?
• Quasars as standard candles I: The physical relation between disc and coronal emission
• Eight new luminous z > 6 quasars selected via SED model fitting of VISTA, WISE and Dark Energy Survey Year 1 Observations
• Constraining the radio-loud fraction of quasars at z>5.5
• Chandra Observations of the Highest Redshift Quasars from the Sloan Digital Sky Survey
• Dust-free quasars in the early Universe
• Dust-Deficient Palomar-Green Quasars and the Diversity of AGN Intrinsic IR Emission
• The deepest X-ray view of high-redshift galaxies: constraints on low-rate black-hole accretion
• Evolution of the X-ray Emission of Radio-Quiet Quasars
• Discovery of 16 New z ~ 5.5 Quasars : Filling in the Redshift Gap of Quasar Color Selection
• Faint progenitors of luminous $z\sim 6$ quasars: why don't we see them?
• The high-redshift (z>3) AGN population in the 4 Ms Chandra Deep Field South
• The Chandra COSMOS Legacy survey: the z>3 sample
• The spectral energy distribution of the redshift 7.1 quasar ULAS J1120+0641
• X-ray spectroscopy of the z=6.4 quasar J1148+5251

Cited by in corpus (67)

• The Assembly of the First Massive Black Holes
• Gemini GNIRS near-infrared spectroscopy of 50 quasars at z>~5.7
• High-redshift AGN in the Chandra Deep Fields: the obscured fraction and space density of the sub-$L_{\ast }$ population
• The X-shooter/ALMA Sample of Quasars in the Epoch of Reionization. II. Black Hole Masses, Eddington Ratios, and the Formation of the First Quasars
• The X-ray properties of $z>6$ quasars: no evident evolution of accretion physics in the first Gyr of the Universe
• The WISSH Quasars Project III. X-ray properties of hyper-luminous quasars
• A dusty compact object bridging galaxies and quasars at cosmic dawn
• The first blazar observed at z>6
• Evidence for Low Radiative Efficiency or Highly Obscured Growth of $z>7$ Quasars
• Revealing the Accretion Physics of Supermassive Black Holes at Redshift z~7 with Chandra and Infrared Observations
• Quasars as standard candles II: The non linear relation between UV and X-ray emission at high redshifts
• Host galaxies of high-redshift quasars: supermassive black hole growth and feedback
• Radiation Hydrodynamical Simulations of the First Quasars
• SRG/eROSITA uncovers the most X-ray luminous quasar at z>6
• Mock catalogs for the extragalactic X-ray sky: simulating AGN surveys with Athena and with the AXIS probe
• The molecular gas content in obscured AGN at z > 1
• Testing AGN outflow and accretion models with CIV and HeII emission line demographics in z=2 quasars
• Impact of X-rays on CO emission from high-z galaxies
• HYPerluminous quasars at the Epoch of ReionizatION (HYPERION). A new regime for the X-ray nuclear properties of the first quasars
• Infrared emission of $z\sim 6$ galaxies: AGN imprints
• First constraints on the AGN X-ray luminosity function at $z\sim 6$ from an eROSITA-detected quasar
• Chandra X-rays from the redshift 7.54 quasar ULAS J1342+0928
• The 500 ks Chandra observation of the z = 6.31 QSO SDSS J1030+0524
• Discovery of the first heavily obscured QSO candidate at $z>6$ in a close galaxy pair
• X-ray Observations of a $z\sim 6.2$ Quasar/Galaxy Merger
• The fraction and kinematics of broad absorption line quasars across cosmic time
• X-ray properties of z>6.5 quasars
• The Fundamental Planes of Black Hole Activity for Radio-Loud and Radio-Quiet Quasars
• Discovery of the most X-ray luminous quasar SRGE J170245.3+130104 at redshift z$\approx 5.5$
• X-ray absorption towards high-redshift sources: probing the intergalactic medium with blazars
• XMM-Newton observations of the extremely X-ray luminous quasar CFHQS J142952+544717=SRGE J142952.1+544716 at redshift z=6.18
• AT 2021loi: A Bowen Fluorescence Flare with a Rebrightening Episode, Occurring in a Previously-Known AGN
• Chandra and Magellan/FIRE follow-up observations of PSO167-13: an X-ray weak QSO at $z=6.515$
• New quasar proximity zone size measurements at $z\sim 6$ using the enlarged XQR-30 sample
• Inception of a first quasar at cosmic dawn
• Deep XMM-Newton Observations of an X-ray Weak, Broad Absorption Line Quasar at $z=6.5$
• X-ray emission from a rapidly accreting narrow-line Seyfert 1 galaxy at z=6.56
• X-ray Properties of Young Radio Quasars at z > 4.5
• The SRG/eROSITA All-Sky Survey: X-ray beacons at late cosmic dawn
• On the Absence of High-Redshift AGNs: Little Growth in the Supermassive Black Hole Population at High Redshifts
• Discovery of Candidate X-ray Jets in High-Redshift Quasars
• Chandra Detection of Three X-ray Bright Quasars at z>5
• Do stellar-mass and super-massive black holes have similar dining habits?
• Probing black hole accretion in quasar pairs at high redshift
• The extremely X-ray luminous radio-loud quasar CFHQS J142952+544717 at $z=6.18$ under Chandra high-angular resolution lens
• Constraints on the X-ray Luminosity Function of AGN at z=5.7-6.4 with the Extragalactic Serendipitous Swift Survey
• No evidence for an Eddington-ratio dependence of X-ray weakness in BALQSOs
• Extreme Primordial Star Formation Enabled by High Redshift Quasars
• An X-ray fading, UV brightening QSO at $z\approx 6$
• Multi-wavelength properties of three new radio-powerful $z\sim 5.6$ quasi-stellar objects discovered from RACS
• Comprehensive view on a $z\sim 6.5$ radio-loud QSO: from the radio to the optical/NIR to the X-ray band
• The intrinsic X-ray luminosity distribution of an optically-selected SDSS quasar population
• The X-Rays wind connection in PG 2112+059
• Exploring Gravitationally-Lensed $z\gtrsim 6$ X-ray AGN Behind the RELICS clusters
• High-$z$ radio Quasars in RACS I: Selection, identification, and multi-wavelength properties
• Probing the parameters of the intergalactic medium using quasars
• HYPERION. Shedding light on the first luminous quasars: A correlation between UV disc winds and X-ray continuum
• The Dawn of Black Holes
• Black hole mass of a quiescent galaxy hosting a Type 1 AGN at z=2.09: Implications for black hole - galaxy co-evolution and AGN quenching at high redshift
• LBT-MODS spectroscopy of high-redshift candidates in the Chandra J1030 field. A newly discovered z$\sim$2.8 large scale structure
• Shedding the envelope: JWST reveals a kiloparsec-scale [OIII]-weak Balmer shell around a z=7.64 quasar
• Revisiting the X-ray-to-UV relation of Quasars in the era of all-sky surveys
• Association of Optical, Ultraviolet and Soft X-ray excess Emissions in AGNs
• Exploratory X-Ray Monitoring of Luminous Radio-Quiet Quasars at High Redshift: Extended Time-Series Analyses and Stacked Imaging Spectroscopy
• Can X-ray Observations Improve Optical-UV-based Accretion-Rate Estimates for Quasars?
• X-Ray Evidence Against the Hypothesis that the Hyper-Luminous z=6.3 Quasar J0100+2802 is Lensed
• The X-ray statistical properties of dust-obscured galaxies detected by eROSITA