Constraining Sub-Parsec Binary Supermassive Black Holes in Quasars with Multi-Epoch Spectroscopy. III. Candidates from Continued Radial Velocity Tests

Abstract

Quasars whose broad emission lines show temporal, bulk radial velocity (RV) shifts have been proposed as candidate sub-parsec (sub-pc), binary supermassive black holes (BSBHs). We identified a sample of 16 BSBH candidates based on two-epoch spectroscopy among 52 quasars with significant RV shifts over a few rest-frame years. The candidates showed consistent velocity shifts independently measured from two broad lines (H$\beta$ and H$\alpha$ or Mg$\mathrm{II}$) without significant changes in the broad-line profiles. Here in the third paper of the series, we present further third- and fourth-epoch spectroscopy for 12 of the 16 candidates for continued RV tests, spanning $\sim$5--15 yr in the quasars' rest frames. Cross-correlation analysis of the broad H$\beta$ calibrated against [O$\mathrm{III}]\lambda 5007$ suggests that 5 of the 12 quasars remain valid as BSBH candidates. They show broad H$\beta$ RV curves that are consistent with binary orbital motion without significant changes in the broad line profiles. Their broad H$\alpha$ (or Mg$\mathrm{II}$) lines display RV shifts that are either consistent with or smaller than those seen in broad H$\beta$. The RV shifts can be explained by a $\sim$0.05--0.1 pc BSBH with an orbital period of $\sim$40--130 yr, assuming a mass ratio of 0.5--2 and a circular orbit. However, the parameters are not well constrained given the few epochs that sample only a small portion of the hypothesized binary orbital cycle. The apparent occurrence rate of sub-pc BSBHs is $\lesssim$13$\pm$5% among all SDSS quasars, with no significant difference in the subsets with and without single-epoch broad line velocity offsets. Dedicated long-term spectroscopic monitoring is still needed to further confirm or reject these BSBH candidates.

arXiv comment38 pages, 11 figures, MNRAS accepted

References in corpus (209)

• Observation of Gravitational Waves from a Binary Black Hole Merger
• emcee: The MCMC Hammer
• The Sloan Digital Sky Survey: Technical Summary
• The Seventh Data Release of the Sloan Digital Sky Survey
• Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies
• The slope of the black-hole mass versus velocity dispersion correlation
• The Baryon Oscillation Spectroscopic Survey of SDSS-III
• Reverberation Measurements for 17 Quasars and the Size-Mass-Luminosity Relations in Active Galactic Nuclei
• A Catalog of Quasar Properties from SDSS DR7
• Testing General Relativity with Present and Future Astrophysical Observations
• The Assembly and Merging History of Supermassive Black Holes in Hierarchical Models of Galaxy Formation
• The Sloan Digital Sky Survey Quasar Catalog V. Seventh Data Release
• Supermassive Black Holes in Galactic Nuclei: Past, Present and Future Research
• The SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Overview and Early Data
• The Relationship Between Luminosity and Broad-Line Region Size in Active Galactic Nuclei
• Using gravitational-wave standard sirens
• The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment
• Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei: I. Comparing the Photoionization and Reverberation Techniques
• Discovery of a binary AGN in the ultraluminous infrared galaxy NGC 6240 using Chandra
• Formation of Galactic Nuclei
• The Radius-Luminosity Relationship for Active Galactic Nuclei: The Effect of Host-Galaxy Starlight on Luminosity Measurements II. The Full Sample of Reverberation-Mapped AGNs
• The NANOGrav 11-year Data Set: High-precision timing of 45 Millisecond Pulsars
• 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 dynamical evolution of massive black hole binaries - I. Hardening in a fixed stellar background
• Gravitational waves from binary supermassive black holes missing in pulsar observations
• Maximum gravitational recoil
• Science with the space-based interferometer eLISA. I: Supermassive black hole binaries
• A Compact Supermassive Binary Black Hole System
• Gravitational Waves Probe the Coalescence Rate of Massive Black Hole Binaries
• Evolution of massive binary black holes
• A massive binary black-hole system in OJ287 and a test of general relativity
• Accretion during the merger of supermassive black holes
• Ejection of hypervelocity stars by the (binary) black hole(s) in the Galactic center
• Massive black hole binary mergers within sub-pc scale gas discs
• Supermassive recoil velocities for binary black-hole mergers with antialigned spins
• Binary Black Hole Accretion From a Circumbinary Disk: Gas Dynamics Inside the Central Cavity
• A possible close supermassive black-hole binary in a quasar with optical periodicity
• The Kozai Mechanism and the Evolution of Binary Supermassive Black Holes
• Quasar Clustering and the Lifetime of Quasars
• The Population of Viscosity- and Gravitational Wave-Driven Supermassive Black Hole Binaries Among Luminous AGN
• The NANOGrav Nine-year Data Set: Limits on the Isotropic Stochastic Gravitational Wave Background
• A systematic search for close supermassive black hole binaries in the Catalina Real-Time Transient Survey
• Low-frequency gravitational radiation from coalescing massive black hole binaries in hierarchical cosmologies
• Alignment of the spins of supermassive black holes prior to coalescence
• Efficient Merger of Binary Supermassive Black Holes in Non-Axisymmetric Galaxies
• Three Dimensional MHD Simulation of Circumbinary Accretion Disks: Disk Structures and Angular Momentum Transport
• Accretion into the Central Cavity of a Circumbinary Disk
• Supermassive black hole binaries in gaseous and stellar circumnuclear discs: orbital dynamics and gas accretion
• The evolution of a supermassive binary caused by an accretion disc
• A Population of Short-Period Variable Quasars from PTF as Supermassive Black Hole Binary Candidates
• Completion of a Survey and Detailed Study of Double-Peaked Emission Lines in Radio-Loud AGNs
• Black-hole binaries, gravitational waves, and numerical relativity
• The Role of Gas in the Merging of Massive Black Holes in Galactic Nuclei. I. Black Hole Merging in a Spherical Gas Cloud
• Understanding Dual AGN Activation in the Nearby Universe
• A Large Systematic Search for Recoiling and Close Supermassive Binary Black Holes
• Massive Black Hole Binary Mergers in Dynamical Galactic Environments
• European Pulsar Timing Array Limits on Continuous Gravitational Waves from Individual Supermassive Black Hole Binaries
• Numerical Relativity and Compact Binaries
• Double-Peaked Low-Ionization Emission Lines in Active Galactic Nuclei
• The Sloan Digital Sky Survey Reverberation Mapping Project: H$\alpha$ and H$\beta$ Reverberation Measurements From First-year Spectroscopy and Photometry
• Getting a kick out of numerical relativity
• A Candidate Sub-Parsec Supermassive Binary Black Hole System
• The Sloan Digital Sky Survey Reverberation Mapping Project: Technical Overview
• Inspiralling Supermassive Black Holes: A New Signpost for Galaxy Mergers
• The Lick AGN Monitoring Project 2011: Spectroscopic Campaign and Emission-Line Light Curves
• On the nature of Seyfert galaxies with high [OIII]5007 blueshifts
• The Structure of the Broad Line Region in AGN: I. Reconstructed Velocity-Delay Maps
• Black hole mergers: can gas discs solve the `final parsec' problem?
• Relativistic boost as the cause of periodicity in a massive black-hole binary candidate
• Binary Black Hole Mergers from Planet-like Migrations
• Fast coalescence of massive black hole binaries from mergers of galactic nuclei: implications for low-frequency gravitational-wave astrophysics
• Dynamics of triple black hole systems in hierarchically merging massive galaxies
• The Sloan Digital Sky Survey Reverberation Mapping Project: Velocity Shifts of Quasar Emission Lines
• Diverse Broad Line Region Kinematic Signatures From Reverberation Mapping
• Massive binary black holes in galactic nuclei and their path to coalescence
• The Local Nanohertz Gravitational-Wave Landscape From Supermassive Black Hole Binaries
• The Gravitational Wave Background from Massive Black Hole Binaries in Illustris: spectral features and time to detection with pulsar timing arrays
• Chandra unveils a binary Active Galactic Nucleus in Mrk463
• Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. V. A New Size-Luminosity Scaling Relation for the Broad-Line Region
• Low-frequency gravitational waves from supermassive black holes
• Supermassive Black Hole Binary Evolution in Axisymmetric Galaxies: the final parsec problem is not a problem
• The final-parsec problem in the collisionless limit
• Dual black holes in merger remnants. II: spin evolution and gravitational recoil
• Binary Black Hole Accretion Flows in Merged Galactic Nuclei
• Massive black hole binaries: dynamical evolution and observational signatures
• Arp 299: a second merging system with two active nuclei?
• Discovery of Four kpc-Scale Binary AGNs
• Recoiling Black Holes in Merging Galaxies: Relationship to AGN Lifetimes, Starbursts, and the M-sigma Relation
• The Nature of Double-Peaked [O III] Active Galactic Nuclei
• A systematic search for massive black hole binaries in SDSS spectroscopic sample
• Chandra Discovery of a Binary Active Galactic Nucleus in Mrk 739
• An all-sky search for continuous gravitational waves in the Parkes Pulsar Timing Array data set
• Hydrodynamics of galaxy mergers with supermassive black holes: is there a last parsec problem ?
• Identifying Supermassive Black Hole Binaries with Broad Emission Line Diagnosis
• Binary Black Hole Accretion During Inspiral and Merger
• NANOGrav Limits on Gravitational Waves from Individual Supermassive Black Hole Binaries in Circular Orbits
• The Sloan Digital Sky Survey Reverberation Mapping Project: First Broad-line Hbeta and MgII Lags at z>~0.3 from six-Month Spectroscopy
• Recoiling black holes: prospects for detection and implications of spin alignment
• Kiloparsec-scale Spatial Offsets in Double-peaked Narrow-line Active Galactic Nuclei. I. Markers for Selection of Compelling Dual Active Galactic Nucleus Candidates
• Recoiling Black Holes in Quasars
• The Sloan Digital Sky Survey Reverberation Mapping Project: No Evidence for Evolution in the M-sigma Relation to z~1
• A Radio Census of Binary Supermassive Black Holes
• The intracluster magnetic field power spectrum in Abell 2382
• Rejection of the Binary Broad-Line Region Interpretation of Double-Peaked Emission Lines in Three Active Galactic Nuclei
• The Origin of Double-Peaked Narrow Lines in Active Galactic Nuclei I: Very Large Array Detections of Dual AGNs and AGN Outflows
• A Runaway Black Hole in COSMOS: Gravitational Wave or Slingshot Recoil?
• A milliparsec supermassive black hole binary candidate in the galaxy SDSS J120136.02+300305.5
• Binary Black Hole Mergers in Gaseous Environments: "Binary Bondi" and "Binary Bondi-Hoyle-Lyttleton" Accretion
• Spectroscopic Indication for a Centi-parsec Supermassive Black Hole Binary in the Galactic Center of NGC 5548
• Evidence for Binary Orbital Motion of a Quasar Broad-Line Region
• Long-Term Profile Variability of Double Peaked Emission Lines in Active Galactic Nuclei
• Chandra X-ray and Hubble Space Telescope Imaging of Optically Selected kiloparsec-Scale Binary Active Galactic Nuclei I. Nature of the Nuclear Ionizing Sources
• Super-massive binary black holes and emission lines in active galactic nuclei
• Constraining sub-Parsec Binary Supermassive Black Holes in Quasars with Multi-Epoch Spectroscopy. I. The General Quasar Population
• The First Spectroscopically Resolved Sub-parsec Orbit of a Supermassive Binary Black Hole
• A Kiloparsec-Scale Binary Active Galactic Nucleus Confirmed by the Expanded Very Large Array
• Binary black hole mergers in gaseous disks: Simulations in general relativity
• A Periodically Varying Luminous Quasar at z=2 from the Pan-STARRS1 Medium Deep Survey: A Candidate Supermassive Black Hole Binary in the Gravitational Wave-Driven Regime
• Dancing to ChaNGa: A Self-Consistent Prediction For Close SMBH Pair Formation Timescales Following Galaxy Mergers
• A Close Nuclear Black Hole Pair in the Spiral Galaxy NGC 3393
• X-shaped radio galaxies as observational evidence for the interaction of supermassive binary black holes and accretion disk at pc scale
• Constraining the Orbit of Supermassive Black Hole Binary 0402+379
• Are we there yet? Time to detection of nanohertz gravitational waves based on pulsar-timing array limits
• Periodic self-lensing from accreting massive black hole binaries
• Multiple black holes in galactic bulges
• Search for Supermassive Black Hole Binaries in the Sloan Digital Sky Survey Spectroscopic Sample
• Collisionless loss-cone refilling: there is no final parsec problem
• Massive Black Hole binaries in gas-rich galaxy mergers; multiple regimes of orbital decay and interplay with gas inflows
• A candidate sub-parsec binary black hole in the Seyfert galaxy NGC 7674
• Constraining Sub-Parsec Binary Supermassive Black Holes in Quasars with Multi-Epoch Spectroscopy. II. The Population with Kinematically Offset Broad Balmer Emission Lines
• Swift coalescence of supermassive black holes in cosmological mergers of massive galaxies
• Long-Term Profile Variability in Active Galactic Nuclei with Double-Peaked Balmer Emission Lines
• A Large Systematic Search for Close Supermassive Binary and Rapidly Recoiling Black Holes - III. Radial Velocity Variations
• Dual black holes in merger remnants. I: linking accretion to dynamics
• Post-Newtonian evolution of massive black hole triplets in galactic nuclei -- III. A robust lower limit to the nHz stochastic background of gravitational waves
• SDSS J1254+0846: A Binary Quasar Caught in the Act of Merging
• Testing the binary hypothesis: pulsar timing constraints on supermassive black hole binary candidates
• Massive black hole pairs in clumpy, self-gravitating circumnuclear disks: stochastic orbital decay
• Gas pile-up, gap overflow, and Type 1.5 migration in circumbinary disks: application to supermassive black hole binaries
• Relativistic Mergers of Supermassive Black Holes and their Electromagnetic Signatures
• The DEEP2 Galaxy Redshift Survey: AEGIS Observations of a Dual AGN at z=0.7
• Formation of galactic nuclei with multiple supermassive black holes at high redshifts
• The final-parsec problem in non-spherical galaxies revisited
• Detection of eccentric supermassive black hole binaries with pulsar timing arrays: Signal-to-noise ratio calculations
• Buried AGNs in Advanced Mergers:Mid-infrared color selection as a dual AGN finder
• X-ray Detection of the Proto Supermassive Binary Black Hole at the Centre of Abell 400
• Modeling of Emission Signatures of Massive Black Hole Binaries: I Methods
• Mergers of Supermassive Black Holes in Astrophysical Environments
• A probable Milli-Parsec Supermassive Binary Black Hole in the Nearest Quasar Mrk 231
• Binary black holes and tori in AGN I. Ejection of stars and merging of the binary
• A Systematic Search for Periodically Varying Quasars in Pan-STARRS1: An Extended Baseline Test in Medium Deep Survey Field MD09
• SDSS J0159+0105: A Radio-Quiet Quasar with a Centi-Parsec Supermassive Black Hole Binary Candidate
• LBQS 0103-2753: A 0.3 Arcsec Binary Quasar
• Radio-Selected Binary Active Galactic Nuclei from the Very Large Array Stripe 82 Survey
• Supermassive black hole pairs in clumpy galaxies at high redshift: delayed binary formation and concurrent mass growth
• A new mechanism for massive binary black hole evolution
• Structure and evolution of circumbinary disks around supermassive black hole (SMBH) binaries
• Adaptive Optics Imaging of QSOs with Double-Peaked Narrow Lines: Are they Dual AGNs?
• A Large Systematic Search for Close Supermassive Binary and Rapidly Recoiling Black Holes - II. Continued Spectroscopic Monitoring and Optical Flux Variability
• Double quasars: probes of black hole scaling relationships and merger scenarios
• Sub-parsec supermassive Binary Quasars: expectations at z<1
• Testing the relativistic Doppler boost hypothesis for supermassive black hole binary candidates
• The nature of massive black hole binary candidates: I. Spectral properties and evolution
• Gravitational waves from merging compact binaries
• Searching for Binary Supermassive Black Holes via Variable Broad Emission Line Shifts: Low Binary Fraction
• NuSTAR Resolves the First Dual AGN above 10 keV in SWIFT J2028.5+2543
• A sub-kpc-scale binary AGN with double narrow-line regions
• Constraints on Black Hole/Host Galaxy Co-evolution and Binary Stalling Using Pulsar Timing Arrays
• How far is quasar UV/optical variability from damped random walk at low frequency?
• Pulsar Timing Constraints on the Fermi Massive Black-Hole Binary Blazar Population
• Search of sub-parsec massive binary black holes through line diagnosis
• Discovery of a dual active galactic nucleus with ~ 8 kpc separation
• Binary Active Galactic Nuclei in Stripe 82: Constraints on Synchronized Black Hole Accretion in Major Mergers
• A Radial Velocity Test for Supermassive Black Hole Binaries as an Explanation for Broad, Double-Peaked Emission Lines in Active Galactic Nuclei
• The Quasar SDSS J1536+0441: An Unusual Double-Peaked Emitter
• The nightmare scenario: measuring the stochastic gravitational-wave background from stalling massive black-hole binaries with pulsar-timing arrays
• Fundamental physics and cosmology with LISA
• Chandra Observations of Galaxy Zoo Mergers: Frequency of Binary Active Nuclei in Massive Mergers
• Astrophysical constraints on massive black hole binary evolution from Pulsar Timing Arrays
• The Sloan Digital Sky Survey Reverberation Mapping Project: the CIV Blueshift, Its Variability, and Its Dependence Upon Quasar Properties
• Multi-messenger approaches to binary supermassive black holes in the "continuous-wave" regime
• Emission Signatures from Sub-parsec Binary Supermassive Black Holes I: Diagnostic Power of Broad Emission Lines
• HST Images and KPNO Spectroscopy of the Binary Black Hole Candidate SDSS J153636.22+044127.0
• Supermassive Black Hole Binaries: The Search Continues
• Pulsars probe the low-frequency gravitational sky: Pulsar Timing Arrays basics and recent results
• Tests of General Relativity and Alternative theories of gravity using Gravitational Wave observations
• Hubble Space Telescope Wide Field Camera 3 Identifies an $r_p$ = 1 Kpc Dual Active Galactic Nucleus in the Minor Galaxy Merger SDSS J0924+0510 at z = 0.1495
• No tension between assembly models of supermassive black hole binaries and pulsar observations
• Evidence from the Very Long Baseline Array that J1502SE/SW are Double Hotspots, not a Supermassive Binary Black Hole
• The Time-Domain Spectroscopic Survey: Target Selection for Repeat Spectroscopy
• Lighthouse in the Dust: Infrared Echoes of Periodic Emission from Massive Black Hole Binaries
• Super massive black holes in star forming gaseous circumnuclear discs
• Detectability of Gravitational Waves from High-Redshift Binaries
• An Electromagnetic Signature of Galactic Black Hole Binaries That Enter Their Gravitational-Wave Induced Inspiral
• The optical variability of SDSS quasars from multi-epoch spectroscopy: I. Results from 60 quasars with $\ge$ six-epoch spectra
• Pulsar timing arrays and the challenge of massive black hole binary astrophysics
• Chandra X-ray and Hubble Space Telescope Imaging of Optically Selected Kiloparsec-Scale Binary Active Galactic Nuclei II: Host Galaxy Morphology and AGN Activity
• Likelihood for Detection of Sub-parsec Supermassive Black Hole Binaries in Spectroscopic Surveys
• Microlensing of Sub-parsec Massive Binary Black Holes in Lensed QSOs: Light Curves and Size-Wavelength Relation
• Gravitational Wave Astronomy: Delivering on the Promises
• The Sloan Digital Sky Survey Reverberation Mapping Project: Composite Lags at $z\lesssim 1$
• Constraints on Two Active Galactic Nuclei in the Merger Remnant COSMOS J100043.15+020637.2
• Recoiling Supermassive Black Hole Escape Velocities from Dark Matter Halos
• Accretion Disks Around Binary Black Holes: A Simple GR-Hybrid Evolution Model
• Line shifts and sub-pc super-massive binary black holes
• The nature of massive black hole binary candidates: II. Spectral energy distribution atlas
• Effects of supermassive binary black holes on gravitational lenses
• Merger Criteria of Multiple Massive Black Holes and the Impact on the Host Galaxy

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