The average absorption properties of broad absorption line quasars at 800 < lambda_rest < 3000 Å, and the underlying physical parameters

Abstract

Broad absorption line quasars (BALQs) present a large diversity in their broad absorption line (BAL) profiles. To investigate what physical parameters underlie this diversity, we construct a sample of BALQs which covers lambda_rest ~ 800-3000 Å, based on the Sloan Digital Sky Survey DR7 quasar catalogue. The average BAL properties are evaluated by taking the ratios of average BALQ spectra to the average spectra of matched samples of non-BALQs, where the matching is based on various emission properties. We find the following properties. (i) There is no detectable Lyman edge associated with the BAL absorbing gas (tau<0.1). (ii) The known increase of average absorption depth with the ionization potential extends to the higher ionization N V and O VI BALs. We also find that the C IV BAL profile is controlled by two parameters. (i) The He II emission EW, which controls the typical velocity of the C IV BAL, but does not affect the absorption depth. (ii) The spectral slope in the 1700-3000 Å range (alpha_UVl), which controls the C IV peak absorption depth, but does not affect the typical velocity. The He II EW and alpha_UVl also control the observed fraction of quasars that are BALQs. We suggest that a lower He II EW may indicate a weaker ionizing continuum, which allows the outflow to reach higher velocities before being overionized, possibly without a need to invoke a shielding gas. A redder continuum may indicate a more inclined system, and a larger covering factor and larger column of the outflow along the line of sight.

22 pages, 14 figures; accepted for publication in MNRAS

References in corpus (13)

• A Catalog of Quasar Properties from SDSS DR7
• The X-ray-to-Optical Properties of Optically-Selected Active Galaxies Over Wide Luminosity and Redshift Ranges
• Biases in Virial Black Hole Masses: An SDSS Perspective
• 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 Intrinsic Fraction of Broad Absorption Line Quasars
• FIRST-2MASS Red Quasars: Transitional Objects Emerging from the Dust
• HST-COS Observations of AGN. I. Ultraviolet Composite Spectra of the Ionizing Continuum and Emission Lines
• Luminous K-band Selected Quasars from UKIDSS
• On the diversity and complexity of absorption line profiles produced by outflows in Active Galactic Nuclei
• BAL Outflow Contribution to AGN Feedback: Frequency of S iv Outflows in the SDSS
• The Nature of LoBAL QSOs: I. SEDs and mid-infrared spectral properties
• Metal enrichment by radiation pressure in active galactic nucleus outflows -- theory and observations

Cited by in corpus (45)

• Evidence of patchy hydrogen reionization from an extreme Ly$\alpha$ trough below redshift six
• X-ray Insights into the Nature of PHL 1811 Analogs and Weak Emission-Line Quasars: Unification with a Geometrically Thick Accretion Disk?
• Dust inflated accretion disc as the origin of the Broad Line Region in Active Galactic Nuclei
• Broad Absorption Line Variability on Multi-Year Timescales in a Large Quasar Sample
• BAL and non-BAL quasars: continuum, emission and absorption properties establish a common parent sample
• Extreme-Velocity Quasar Outflows and the Role of X-ray Shielding
• The Sloan Digital Sky Survey Reverberation Mapping Project: Rapid CIV Broad Absorption Line Variability
• Mining for Dust in Type 1 Quasars
• Evidence for Photoionization Driven Broad Absorption Line Variability
• Detection of Rest-frame Optical Lines from X-shooter Spectroscopy of Weak Emission Line Quasars
• Does the X-ray outflow quasar PDS 456 have a UV outflow at 0.3c?
• On the structure and energetics of quasar broad absorption-line outflows
• Radiation pressure confinement - IV. Application to broad absorption line outflows
• Testing AGN outflow and accretion models with CIV and HeII emission line demographics in z=2 quasars
• Line-driven radiative outflows in luminous quasars
• Evidence that most type 1 AGN are reddened by dust in the host ISM
• High redshift extremely red quasars in X-rays
• A Variable PV Broad Absorption Line and Quasar Outflow Energetics
• Outflow and hot dust emission in broad absorption line quasars
• Evidence for quasar fast outflows being accelerated at the scale of tens of parsecs
• What controls the UV-to-X-ray continuum shape in quasars?
• Narrow absorption lines complex I: one form of broad absorption line
• Discovery of Extremely Broad Balmer Absorption Lines in SDSS J152350.42+391405.2
• Survey of Extremely High-velocity Outflows in Sloan Digital Sky Survey Quasars
• HST and Ground-Based Spectroscopy of Quasar Outflows: From Mini-BALs to BALs
• Characterizing Quasar CIV Emission-line Measurements from Time-resolved Spectroscopy
• On the origins of C IV absorption profile diversity in broad absorption line quasars
• C IV BAL disappearance in a large SDSS QSO sample
• The Ubiquitous Imprint of Radiative Acceleration in the Mean Absorption Spectrum of Quasar Outflows
• Variability of QSOs with variable regions in broad absorption troughs from the Sloan Digital Sky Survey
• On the Emergence of Thousands of Absorption Lines in the Quasar PG1411+442: A Clumpy High-Column Density Outflow from the Broad Emission-Line Region?
• Placing LOFAR-detected quasars in CIV emission space: implications for winds, jets and star formation
• Quasars with PV broad absorption in BOSS data release 9
• Galactic Winds across the Gas-Rich Merger Sequence: I. Highly Ionized N V and O VI Outflows in the QUEST Quasars
• The Sloan Digital Sky Survey Reverberation Mapping Project: Biases in z>1.46 Redshifts due to Quasar Diversity
• Evidence for Fluorescent Fe II Emission from Extended Low Ionization Outflows in Obscured Quasars
• Radiation-pressure Waves and Multiphase Quasar Outflows
• Variability of broad absorption lines in a QSO SDSS J022844.09+000217.0 on multi-year timescales
• Connection between Emission and Absorption Outflows through the Study of Quasars with Extremely-High Velocity Outflows
• The X-Rays wind connection in PG 2112+059
• Proving strong magnetic fields near to the central black hole in the quasar PG0043+039 via cyclotron lines
• The peculiar optical-UV X-ray spectra of the X-ray weak quasar PG 0043+039
• X-ray selected broad absorption line quasars in SDSS-V: BALs and non-BALs span the same range of X-ray properties
• Hubble Space Telescope Observations of BALQSO Ton 34 Reveal a Connection between the Broad Line Region and the BAL Outflow
• Exploring the quasar disc-wind-jet connection with LoTSS and SDSS