The Nature of Luminous Quasars with Very Large C IV Equivalent Widths
arXiv:2206.11631 · doi:10.3847/1538-4357/ac7a36
Abstract
We report results for a complete sample of ten luminous radio-quiet quasars with large C IV equivalent widths (EW > 150 A). For 8/10 we performed Chandra snapshot observations. We find that, in addition to the enhanced C IV line EW, their He II and Mg II lines are enhanced, but the C III] line is not. Their X-ray emission is substantially stronger than expected from their ultraviolet luminosity. Additionally, these large C IV EW quasars show small C IV blueshifts and possibly low Eddington ratios, suggesting they are "extreme low Eigenvector 1 (EV1)" quasars. The mean excess He II EW is well-matched by Radiation Pressure Compression (RPC) photoionization models, with the harder aox ionizing spectrum. However, these results do not reproduce well the enhancement pattern of the C IV, Mg II, and C III] EWs, or the observed high C IV/Mg II ratio. RPC calculations indicate that the C IV/Mg II line ratio is an effective metallicity indicator, and models with sub-Solar metallicity gas and a hard ionizing continuum reproduce well the enhancement pattern of all four ultraviolet lines. We find that the C IV/Mg II line ratio in quasars is generally correlated with the excess X-ray emission. Extremely high EV1 quasars are characterized by high metallicity and suppressed X-ray emission. The underlying mechanism relating gas metallicity and X-ray emission is not clear, but may be related to radiation-pressure driven disk winds, which are enhanced at high metallicity, and consequent mass loading reducing coronal X-ray emission.
arXiv comment17 pages, 9 figures, accepted for publication in ApJ
References in corpus (45)
- The Sloan Digital Sky Survey: Technical Summary
- The Zwicky Transient Facility: System Overview, Performance, and First Results
- Composite Quasar Spectra From the Sloan Digital Sky Survey
- A Catalog of Quasar Properties from SDSS DR7
- Some Aspects of Measurement Error in Linear Regression of Astronomical Data
- First Results from the Catalina Real-time Transient Survey
- The SDSS Quasar Survey: Quasar Luminosity Function from Data Release Three
- Biases in Virial Black Hole Masses: An SDSS Perspective
- Black Hole Mass and Eddington Ratio as Drivers for the Observable Properties of Radio-Loud and Radio-Quiet QSOs
- Piecing Together the X-ray Background: Bolometric Corrections for Active Galactic Nuclei
- The Sloan Digital Sky Survey Quasar Catalog: Fourteenth Data Release
- Unification of Luminous Type 1 Quasars through CIV Emission
- Bolometric luminosities and Eddington ratios of X-ray selected Active Galactic Nuclei in the XMM-COSMOS survey
- The X-ray Properties of the Most-Luminous Quasars from the Sloan Digital Sky Survey
- Red and Reddened Quasars in the Sloan Digital Sky Survey
- The diversity of quasars unified by accretion and orientation
- Bayesian Estimation of Hardness Ratios: Modeling and Computations
- Comparing Single-Epoch Virial Black Hole Mass Estimators for Luminous Quasars
- The Hard X-ray Spectrum as a Probe for Black-Hole Growth in Radio-Quiet Active Galactic Nuclei
- Improved redshifts for SDSS quasar spectra
- Black Hole Growth to z = 2 - I: Improved Virial Methods for Measuring M_BH and L/L_Edd
- Near Infrared Spectroscopy of High Redshift Active Galactic Nuclei. I. A Metallicity-Accretion Rate Relationship
- A statistical relation between the X-ray spectral index and Eddington ratio of active galactic nuclei in deep surveys
- Coronal outflow dominated accretion discs: a new possibility for low luminosity black holes?
- X-ray Insights into the Nature of PHL 1811 Analogs and Weak Emission-Line Quasars: Unification with a Geometrically Thick Accretion Disk?
- Colour corrections for high redshift objects due to intergalactic attenuation
- Are Optically-Selected Quasars Universally X-Ray Luminous? X-Ray/UV Relations in Sloan Digital Sky Survey Quasars
- The Disk-Jet Connection in Microquasars and AGN
- On the origin of the C IV Baldwin effect in AGN
- Radiation pressure confinement - II. Application to the broad line region in active galactic nuclei
- The -- relation and corona-disk-jet connection in optically selected radio-loud quasars
- New constraints on the X-ray spectral properties of type 1 AGN
- The correlations between optical/UV broad lines and X-ray emission for a large sample of quasars
- Connecting the X-ray properties of weak-line and typical quasars: testing for a geometrically thick accretion disk
- Transient jet formation and state transitions from large-scale magnetic reconnection in black hole accretion discs
- Dust Reverberation Mapping in Distant Quasars from Optical and Mid-Infrared Imaging Surveys
- The chemical properties of low-redshift QSOs
- Optical, UV, and X-ray Clues to the Nature of Narrow Line AGNs
- Black hole magnetosphere with small scale flux tubes--II. Stability and dynamics
- Sensitive Chandra coverage of a representative sample of weak-line quasars: revealing the full range of X-ray properties
- Differences Between The Optical/Uv Spectra Of X-Ray Bright And X-Ray Faint QSOs
- What controls the UV-to-X-ray continuum shape in quasars?
- Black hole magnetosphere with small scale flux tubes
- Steep Hard-X-ray Spectra Indicate Extremely High Accretion Rates in Weak Emission-Line Quasars
- Characterizing Quasar CIV Emission-line Measurements from Time-resolved Spectroscopy
Cited by in corpus (6)
- Testing AGN outflow and accretion models with CIV and HeII emission line demographics in z=2 quasars
- Chemical abundances along the quasar main sequence
- Strong and Rapid X-ray Variability of the Super-Eddington Accreting Quasar SDSS J081456.10+532533.5
- Shedding New Light on Weak Emission-Line Quasars in the C-H Parameter Space
- Photometric Selection of type 1 Quasars in the XMM-LSS Field with Machine Learning and the Disk-Corona Connection
- Spectroscopic Quasar Anomaly Detection (SQuAD) I: Rest-Frame UV Spectra from SDSS DR16