Exploratory Study of Transverse Proximity Effect around BAL Quasars

Abstract

We aim to find out the reason why there exists an anisotropic HI absorption around quasars; i.e., the environments around quasars are highly biased toward producing strong HI absorption in transverse direction while there exists a significant deficit of HI absorption within a few Mpc of quasars along line-of-sight. The most plausible explanation for this opposite trend is that the transverse direction is shadowed from the quasar UV radiation due to dust torus. However, a critical weakness of this idea is that we have no information on inclination angle of our sightline relative to the torus. In this study, we examine environments of quasars with broad absorption troughs in their spectra (i.e., BAL quasars) because it is widely believed that BAL troughs are observed if the central continuum is viewed from the side through their powerful outflows near the dust torus. With closely separated 12 projected quasar pairs at different redshift with separation angle of $\theta$$<$120${}^{\prime \prime }$, we examine HI absorption at foreground BAL quasars in spectra of background quasars. We confirm there exist optically thick gas around two of 12 BAL quasars, and that the mean HI absorption strength is EW${}_{\mathrm{rest}}$$\sim$1A. These are consistent to the past results around non-BAL quasars, although not statistically significant. However, the origins of optically thick HI absorbers around BAL and non-BAL quasars could be different since their column densities are different by $\sim$3 orders of magnitude. The larger sample would be required for narrowing down possible scenarios for the anisotropic HI absorption around quasars.

arXiv comment17 pages, 10 figures, accepted for publication in ApJ

References in corpus (38)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• The Dust Content and Opacity of Actively Star-Forming Galaxies
• Composite Quasar Spectra From the Sloan Digital Sky Survey
• Radiative transfer in a clumpy universe: IV. New synthesis models of the cosmic UV/X-ray background
• Cosmological Evolution of the Hard X-ray AGN Luminosity Function and the Origin of the Hard X-ray Background
• Dynamics of line-driven disk winds in Active Galactic Nuclei
• A Structure for Quasars
• The Rest-Frame Extreme Ultraviolet Spectral Properties of QSOs
• The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release
• The Sloan Digital Sky Survey Quasar Catalog: twelfth data release
• Unusual Broad Absorption Line Quasars from the Sloan Digital Sky Survey
• The Spatial Clustering of Star-forming Galaxies at Redshifts 1.4<z<3.5
• Properties of Radio-Selected Broad Absorption-Line Quasars from the FIRST Survey
• The first ultraviolet quasar stacked spectrum at z=2.4 from WFC3
• A Direct Precision Measurement of the Intergalactic Lyman-alpha Opacity at 2<z<4.2
• A strong redshift dependence of the broad absorption line quasar fraction
• The Intrinsic Fraction of Broad Absorption Line Quasars
• The Sloan Digital Sky Survey Reverberation Mapping Project: Velocity Shifts of Quasar Emission Lines
• Quasars Probing Quasars I: Optically Thick Absorbers Near Luminous Quasars
• A global view of the inner accretion and ejection flow around super massive black holes: radiation driven accretion disk winds in a physical context
• The FIRST-2MASS Red Quasar Survey II: An anomalously high fraction of LoBALs in searches for dust-reddened quasars
• Broad Absorption Line Variability on Multi-Year Timescales in a Large Quasar Sample
• A Uniform Analysis of the Ly-alpha forest at z = 0 - 5: II. Measuring the mean intensity of the extragalactic ionizing background using the proximity effect
• Quasars Probing Quasars VI. Excess HI Absorption Within One Proper Mpc of z~2 Quasars
• A Principal Component Analysis of quasar UV spectra at z~3
• Ionizing radiation fluctuations and large-scale structure in the Lyman-alpha forest
• Quasars Probing Quasars IV: Joint Constraints on the Circumgalactic Medium from Absorption and Emission
• Predicting QSO Continua in the Ly Alpha Forest
• The Transverse Proximity Effect: A Probe to the Environment, Anisotropy, and Megayear Variability of QSOs
• Evidence that FeLoBALs may signify the transition between an ultraluminous infrared galaxy and a quasar
• The transverse proximity effect in the z ~ 2 Lyman-alpha forest suggests QSO episodic lifetimes of ~1 Myr
• Star formation history, dust attenuation and extragalactic background light
• Evolutive Unification in Composite Active Galactic Nuclei
• Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). XI. Proximity Zone Analysis for Faint Quasar Spectra at z~6
• Probing the environment of high-z quasars using the proximity effect in projected quasar pairs
• On probing the properties of QSOs through their proximity effects on the intergalactic medium
• MCMC-based Voigt Profile fitting to a Mini-BAL System in the Quasar UM675
• Constraining the ratio of median pixel optical depth profile around z ~ 4 quasars using the longitudinal proximity effect

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