Unveiling the Intrinsic X-ray Properties of Broad Absorption Line Quasars with a Relatively Unbiased Sample

Abstract

There is growing evidence of a higher intrinsic fraction of broad absorption line quasars (BALQSOs) than that obtained in optical surveys, on which most previous X-ray studies of BALQSOs have focused. Here we present Chandra observations of 18 BALQSOs at $z\sim 2$, selected from a near-infrared (2MASS) sample, where the BALQSO fraction is likely to be close to the intrinsic fraction. We measure photon indices using the stacked spectra of the optically-faint ($i-K_s\ge 2.3$ mag) and optically-bright ($i-K_s<2.3$ mag) samples to be $\Gamma \simeq 1.5$--$2.1$. We constrain their intrinsic column density by modelling the X-ray fractional hardness ratio, finding a mean column density of $3.5\times 10^{22}$ \cmsq\ assuming neutral absorption. We incorporate SDSS optical measurements (rest frame UV) to study the broadband spectral index between the X-ray and UV bands, and compare this to a large sample of normal quasars. We estimate that the optically-faint BALQSOs are X-ray weaker than the optically-bright ones, and the entire sample of BALQSOs are intrinsically X-ray weak when compared to normal AGN. Correcting for magnification of X-ray emission via gravitational lensing by the central black hole viewed at large inclination angles makes these BALQSOs even more intrinsically X-ray weak. Finally, we estimate AGN kinetic feedback efficiencies of a few percent for an X-ray wind of $0.3c$ in high-ionization BALQSOs. Combined with energy carried by low-ionization BALQSOs and UV winds, the total kinetic energy in BALQSOs can be sufficient to provide AGN kinetic feedback required to explain the co-evolution between black holes and host galaxies.

Accepted for publication in ApJ, 12 pages, 9 figures, 4 tables

References in corpus (19)

• Biases in Virial Black Hole Masses: An SDSS Perspective
• The X-ray-to-Optical Properties of Optically-Selected Active Galaxies Over Wide Luminosity and Redshift Ranges
• The X-ray Properties of the Most-Luminous Quasars from the Sloan Digital Sky Survey
• A Catalog of Broad Absorption Line Quasars in Sloan Digital Sky Survey Data Release 5
• The Radio-Loud Fraction of Quasars is a Strong Function of Redshift and Optical Luminosity
• The Intrinsic Fraction of Broad Absorption Line Quasars
• An Exploratory Chandra Survey of a Well-Defined Sample of 35 Large Bright Quasar Survey Broad Absorption Line Quasars
• On the Fraction of Quasars with Outflows
• Quasar Outflows and AGN Feedback in the Far UV: HST/COS Observations of QSO HE0238-1904
• X-Ray and Optical Microlensing in the Lensed Quasar PG 1115+080
• Luminous K-band Selected Quasars from UKIDSS
• The Physical Nature of Polar Broad Absorption Line Quasars
• Weak Hard X-ray Emission from Two Broad Absorption Line Quasars Observed with NuSTAR: Compton-thick Absorption or Intrinsic X-ray Weakness?
• Dependence of the BALQSO fraction on Radio Luminosity
• Confirmation of a correlation between the X-ray luminosity and spectral slope of AGNs in the Chandra Deep Fields
• Tracing the Outflow of a z=0.334 FeLoBAL: New Constraints from Low-Ionization Absorbers in FBQS J1151+3822
• XMM-Newton and Chandra Spectroscopy of the Variable High-Energy Absorption of PG 1115+080: Refined Outflow Constraints
• The Optical-Radio Mapping: the kinetic efficiency of Radio-Loud AGNs
• First detection of hard X-ray photons in the soft X-ray transient Narrow-Line Seyfert 1 galaxy WPVS 007: The X-ray photon distribution observed by Swift

Cited by in corpus (12)

• Weak Hard X-ray Emission from Broad Absorption Line Quasars: Evidence for Intrinsic X-ray Weakness
• Evidence for Photoionization Driven Broad Absorption Line Variability
• Stratified disc wind models for the AGN broad-line region: ultraviolet, optical and X-ray properties
• Radiation pressure confinement - IV. Application to broad absorption line outflows
• The origin of radio emission in broad absorption line quasars: Results from the LOFAR Two-metre Sky Survey
• Connecting radio emission to AGN wind properties with Broad Absorption Line Quasars
• No evidence for an Eddington-ratio dependence of X-ray weakness in BALQSOs
• Fraction of broad absorption line quasars in different radio morphologies
• Submm-bright X-ray absorbed QSOs at z~2: insights into the co-evolution of AGN and star-formation
• X-ray selected BALQSOs
• Swift Monitoring Observations of Mrk 231: Detection of Ultraviolet Variability
• Broadband nuclear emission in two radio-loud BAL quasars