The Civ line width distribution for quasars and its implications for broad-line region dynamics and virial mass estimation

Abstract

We perform an extensive analysis of the Civ line in three large spectroscopic surveys of quasars. Differing approaches for fitting the Civ line can be found in the literature, and we compare the most common methods to highlight the relative systematics associated with each. We develop a line fitting procedure and apply it to the Civ line in spectra from the SDSS, 2QZ and 2SLAQ surveys. Our results are compared with a previous study of the Mgii line in the same sample. Civ tends to be broader than the Mgii line in spectra that have both, and the average ratio between the lines is consistent with a simplistic model for a photoionised, virialised and stratified broad-line region. There is a statistically significant correlation between the widths of the Civ and Mgii lines. However, the correlation is weak, and the scatter around a best fit is only marginally less than the full dynamic range of line widths. Motivated by previous work, we examine the dispersion in the distribution of Civ line widths. We find that the dispersion in Civ line widths is essentially independent of both redshift and luminosity. This is in stark contrast to the Mgii line, which shows a strong luminosity dependence. Finally we consider our results in terms of their implications for virial black hole mass estimation. The inconsistency between Mgii and Civ line widths in single spectra, combined with the differing behaviour of the Mgii and Civ line width distributions, indicates that there must be an inconsistency between Mgii and Civ virial mass estimators. Furthermore, the level of intrinsic dispersion in Mgii and Civ line widths contributes less dynamic range to virial mass estimates than the error associated with the estimates. The indication is that the line width term in these UV virial mass estimators may be essentially irrelevant with respect to the typical uncertainty on a mass estimate.

Accepted for publication in MNRAS

References in corpus (40)

• The 2.5 m Telescope of the Sloan Digital Sky Survey
• Composite Quasar Spectra From the Sloan Digital Sky Survey
• Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation-Mapping Database
• Determining Central Black Hole Masses in Distant Active Galaxies and Quasars. II. Improved Optical and UV Scaling Relationships
• Spectral Energy Distributions and Multiwavelength Selection of Type 1 Quasars
• Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Quasar Sample
• The SDSS Quasar Survey: Quasar Luminosity Function from Data Release Three
• The Fifth Data Release of the Sloan Digital Sky Survey
• The 2dF QSO Redshift Survey - XII. The spectroscopic catalogue and luminosity function
• The cosmological evolution of quasar black-hole masses
• An Empirical Ultraviolet Template for Iron Emission in Quasars as Derived from I Zw 1
• Biases in Virial Black Hole Masses: An SDSS Perspective
• The Sloan Digital Sky Survey Quasar Catalog IV. Fifth Data Release
• Systematic Effects in Measurement of Black Hole Masses by Emission-Line Reverberation of Active Galactic Nuclei: Eddington Ratio and Inclination
• Reverberation Mapping of High-Luminosity Quasars: First Results
• Measuring the black hole masses of high redshift quasars
• Determining Central Black Hole Masses in Distant Active Galaxies
• A Catalog of Broad Absorption Line Quasars from the Sloan Digital Sky Survey Third Data Release
• Broad Emission Line Shifts in Quasars: An Orientation Measure for Radio-Quiet Quasars?
• The Anglo-Australian Observatory's 2dF Facility
• What controls the C IV line profile in active galactic nuclei?
• CIV 1549 as an Eigenvector 1 Parameter for Active Galactic Nuclei
• The Black Hole Mass - Galaxy Bulge Relationship for QSOs in the SDSS DR3
• The 2dF QSO Redshift Survey - V. The 10k catalogue
• The 2dF-SDSS LRG and QSO Survey: The z<2.1 Quasar Luminosity Function from 5645 Quasars to g=21.85
• The Intrinsic Fraction of Broad Absorption Line Quasars
• Black-Hole Mass and Growth Rate at High Redshift
• The Mass of the Central Black Hole in the Seyfert Galaxy NGC 3783
• On the variability of quasars: a link between Eddington ratio and optical variability?
• Conference Summary: AGN Physics with the Sloan Digital Sky Survey
• The 2dF-SDSS LRG and QSO Survey: The spectroscopic QSO catalogue
• Predicted FeII Emission-Line Strengths from Active Galactic Nuclei
• The correlation of line strength with luminosity and redshift from composite QSO spectra
• Orientation dependency of broad-line widths in quasars and consequences for black-hole mass estimation
• Spectral Properties From Lyman-alpha to H-alpha For An Essentially Complete Sample of Quasars I: Data
• The BH mass of nearby QSOs: a comparison of the bulge luminosity and virial methods
• Determination of the Central Mass in Active Galactic Nuclei Using Cross-Correlation Lags and Velocity Dispersions
• The evolution of host mass and black hole mass in QSOs from the 2dF QSO Redshift Survey
• Eddington ratios of faint AGN at intermediate redshift: Evidence for a population of half-starved black holes
• The Effect of Variability on the Estimation of Quasar Black Hole Masses

Cited by in corpus (55)

• Comparing Single-Epoch Virial Black Hole Mass Estimators for Luminous Quasars
• Black Hole Growth to z = 2 - I: Improved Virial Methods for Measuring M_BH and L/L_Edd
• The LABOCA Survey of the Extended Chandra Deep Field South: Clustering of submillimetre galaxies
• Black Hole Mass Estimates Based on CIV are Consistent with Those Based on the Balmer Lines
• Active galactic nuclei at z~1.5: II. Black Hole Mass estimation by means of broad emission lines
• Type 1 low z AGN. I. Emission properties
• The Demographics of Broad-Line Quasars in the Mass-Luminosity Plane. I. Testing FWHM-Based Virial Black Hole Masses
• The broad emission-line region: the confluence of the outer accretion disc with the inner edge of the dusty torus
• Are Outflows Biasing Single-Epoch CIV Black Hole Mass Estimates?
• Black-Hole Mass and Growth Rate at z~4.8: A Short Episode of Fast Growth Followed by Short Duty Cycle Activity
• Microlensing of Quasar Broad Emission Lines: Constraints on Broad Line Region Size
• Calibrating CIV-based black hole mass estimators
• Geometry and inclination of the broad line region in blazars
• Are there reliable methods to estimate the nuclear orientation of Seyfert galaxies?
• Simulations of the OzDES AGN Reverberation Mapping Project
• CIV Line-Width Anomalies: The Perils of Low S/N Spectra
• Mean and Extreme Radio Properties of Quasars and the Origin of Radio Emission
• CIV Black Hole Mass Measurements with the Australian Dark Energy Survey (OzDES)
• Zooming into the broad line region of the gravitationally lensed quasar Q2237+0305 = the Einstein Cross: III. Determination of the size and structure of the CIV and CIII] emitting regions using microlensing
• No signs of star formation being regulated in the most luminous quasars at z~2 with ALMA
• Extending the Calibration of CIV-Based Single-Epoch Black Hole Mass Estimators for Active Galactic Nuclei
• Simultaneous Ultraviolet and Optical Emission-line Profiles of Quasars: Implications for Black Hole Mass Determination
• Discovery of 24 radio-bright quasars at $4.9\le z\le 6.6$ using low-frequency radio observations
• Black hole mass estimates in quasars - A comparative analysis of high- and low-ionization lines
• Orientation effects in quasar spectra: The broad- and narrow-line regions
• The Sloan Digital Sky Survey Reverberation Mapping Project: the CIV Blueshift, Its Variability, and Its Dependence Upon Quasar Properties
• Super-Eddington Accretion in the WISE-Selected Extremely Luminous Infrared Galaxy W2246-0526
• Synchrotron and inverse-Compton emission from blazar jets - IV. BL Lac type blazars and the physical basis for the blazar sequence
• Can we improve CIV-based single epoch black hole mass estimations?
• The Sloan Digital Sky Survey Reverberation Mapping Project: An Investigation of Biases in CIV Emission-Line Properties
• Microlensing and Intrinsic Variability of the Broad Emission Lines of Lensed Quasars
• Differential interferometry of QSO broad line regions I: improving the reverberation mapping model fits and black hole mass estimates
• MHD Disc Winds and Linewidth Distributions
• Ultraviolet Emission-Line Correlations in Hubble/COS Spectra of Active Galactic Nuclei: Single-Epoch Black Hole Masses
• The behavior of quasar C IV emission-line properties with orientation
• The clustering of submillimeter galaxies detected with ALMA
• The hyperluminous X-ray source candidate in IC 4320: another HLX bites the dust
• Gravitational lens system SDSS J1339+1310: microlensing factory and time delay
• Reaching the Peak of the quasar spectral energy distribution - II. Exploring the accretion disc, dusty torus and host galaxy
• An FMOS Survey of moderate-luminosity broad-line AGN in COSMOS, SXDS and E-CDF-S
• The environment of weak emission-line quasars
• Faint COSMOS AGN at z~3.3 - I. Black Hole Properties and Constraints on Early Black Hole Growth
• High-redshift quasars along the Main Sequence
• Do quasar broad-line velocity widths add any information to virial black hole mass estimates?
• Mid-Infrared Selected Quasars I: Virial Black Hole Mass and Eddington Ratios
• UV spectral diagnostics for low redshift quasars: estimating physical conditions and radius of the Broad Line Region
• The Sloan Digital Sky Survey Reverberation Mapping Project: Biases in z>1.46 Redshifts due to Quasar Diversity
• Probing black hole accretion in quasar pairs at high redshift
• Rest-frame UV single-epoch black hole mass estimates of low-luminosity AGN at intermediate redshifts
• Magnetohydrodynamic DiscWinds and LineWidth Distributions.II
• Composite reverberation mapping
• The Energetics of Launching the Most Powerful Jets in Quasars: A Study of 3C82
• The Herschel-SPIRE Legacy Survey (HSLS): the scientific goals of a shallow and wide submillimeter imaging survey with SPIRE
• The Energetics of the Central Engine in the Powerful Quasar, 3C298
• On the non-evolution of the dependence of black hole masses on bolometric luminosities for QSOs