The X-ray Properties of the Most-Luminous Quasars from the Sloan Digital Sky Survey

Abstract

Utilizing 21 new Chandra observations as well as archival Chandra, ROSAT, and XMM-Newton data, we study the X-ray properties of a representative sample of 59 of the most optically luminous quasars in the Universe (M_i~~-29.3 to -30.2) spanning a redshift range of z~~1.5-4.5. Our full sample consists of 32 quasars from the Sloan Digital Sky Survey (SDSS) Data Release 3 (DR3) quasar catalog, two additional objects in the DR3 area that were missed by the SDSS selection criteria, and 25 comparably luminous quasars at z>~4. This is the largest X-ray study of such luminous quasars to date. By jointly fitting the X-ray spectra of our sample quasars, excluding radio-loud and broad absorption line (BAL) objects, we find a mean X-ray power-law photon index of Gamma=1.92^{+0.09}_{-0.08} and constrain any neutral intrinsic absorbing material to have a mean column density of N_H<~2x10^{21} cm^{-2}. We find, consistent with other studies, that Gamma does not change with redshift, and we constrain the amount of allowed Gamma evolution for the most-luminous quasars. Our sample, excluding radio-loud and BAL quasars, has a mean X-ray-to-optical spectral slope of a_ox=-1.80+/-0.02, as well as no significant evolution of a_ox with redshift. We also comment upon the X-ray properties of a number of notable quasars, including an X-ray weak quasar with several strong narrow absorption-line systems, a mildly radio-loud BAL quasar, and a well-studied gravitationally lensed quasar.

arXiv comment18 pages (emulateapj), 11 figures. Accepted for publication in The Astrophysical Journal

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• Shedding the envelope: JWST reveals a kiloparsec-scale [OIII]-weak Balmer shell around a z=7.64 quasar
• X-ray Unveiling Events in a z~1.6 Active Galactic Nucleus in the 7 Ms Chandra Deep Field-South
• Exploring the possible evolution of the mass density power-law index of strong gravitational lenses with a model-independent method
• H1821+643: The most X-ray and infrared luminous AGN in the Swift/BAT survey in the process of rapid stellar and supermassive black hole mass assembly
• A comparison of cosmological models with high-redshift quasars
• Revisiting the X-ray-to-UV relation of Quasars in the era of all-sky surveys
• The Morphology of Dwarf Galaxies Hosting Variable Active Galactic Nuclei
• X-ray Absorption and Reprocessing in the $z\sim 2.5$ Lensed Quasar 2MASS J1042+1641
• AGN feeding along a one-armed spiral in NGC 4593: A study using ALMA CO(2-1) observations
• Spectroscopic confirmation of the galaxy clusters CARLA J0950+2743 at z=2.363, and CARLA-Ser J0950+2743 at z=2.243
• Spectral Properties Of Populations Behind The Coherence In Spitzer Near-Infrared And Chandra X-Ray Backgrounds
• Exploratory X-Ray Monitoring of Luminous Radio-Quiet Quasars at High Redshift: Extended Time-Series Analyses and Stacked Imaging Spectroscopy
• Strong X-ray Variability of I Zwicky 1: Obscuration from Clumpy Accretion-Disk Winds
• How black hole activity may influence exoplanetary evolution in our Galaxy
• PHL 6625: A Minor Merger-Associated QSO Behind NGC 247
• Early Stages of Dusty Tori: The First Infrared Spectra from a Highly Multiscale Quasar Simulation
• Gemini Near Infrared Spectrograph$-$Distant Quasar Survey: the Chandra View
• Investigating the Accretion Nature of Binary Supermassive Black Hole Candidate SDSS J025214.67-002813.7
• Can X-ray Observations Improve Optical-UV-based Accretion-Rate Estimates for Quasars?
• The X-ray statistical properties of dust-obscured galaxies detected by eROSITA
• AGILE: an end-to-end Rubin-LSST simulation of AGNs, galaxies, and stars I. Software description and first data release
• The physical relation between disc and coronal emission in quasars