Detection of a variable stratified UFO with velocities 0.1c and 0.3c, extreme mass outflow rates, and kinetic powers of 1-10% of bolometric luminosity in quasar WISSH13 at z=3.294.
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Unified Schemes for Radio-Loud Active Galactic Nuclei
Mixed citation behavior. Most common role is background (60%).
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abstract
The appearance of active galactic nuclei (AGN) depends so strongly on orientation that our current classification schemes are dominated by random pointing directions instead of more interesting physical properties. Light from the centers of many AGN is obscured by optically thick circumnuclear matter and in radio-loud AGN, bipolar jets emanating from the nucleus emit light that is relativistically beamed along the jet axes. Understanding the origin and magnitude of radiation anisotropies in AGN allows us to unify different classes of AGN; that is, to identify each single, underlying AGN type that gives rise to different classes through different orientations. This review describes the unification of radio-loud AGN, which include radio galaxies, quasars, and blazars. We describe the classification and properties of AGN and summarize the evidence for anisotropic emission. We outline the two most plausible unified schemes for radio-loud AGN, one linking quasars and luminous radio galaxies and another linking BL~Lac objects and less luminous radio galaxies. Using the formalism appropriate to samples biased by relativistic beaming, we show the population statistics for two schemes are in accordance with available data. We analyze the possible connections between low- and high-luminosity radio-loud AGN. We review potential difficulties with unification and conclude that none currently constitutes a serious problem. We discuss likely complications to unified schemes that are suggested by realistic physical considerations; these will be important to consider when more comprehensive data for larger complete samples become available. We conclude with a list of the ten questions we believe are the most pressing in this field.
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representative citing papers
Magnetized disk models lower the thermal-viscous instability threshold to Eddington ratios of 0.01-0.03 and yield limit-cycle timescales of months to years, jointly matching observations in five CLAGN only when the inner disk is strongly magnetized.
An analytical derivation of maximum neutrino flux in the one-zone leptohadronic model shows predicted fluxes remain below IceCube levels for neutrino-candidate blazars.
Red quasars are intrinsically X-ray weak with low alpha_OX values, tracing a distinct evolutionary stage of suppressed black hole accretion relative to stellar mass growth.
A causal machine-learning model using variability features from Fermi-LAT light curves predicts blazar flare activity within 90 days with 86% recall on held-out data for one FSRQ.
New publicly available X-ray table models RXToPo and RXagn1 with realistic AGN geometries (torus, polar cone, disk, BLR) generated via RefleX and tested on NGC 424.
Confirmation of 77 new heavily reddened quasars at 1.5 < z < 3.9 with high luminosities and extinctions, showing they are deficient in hot and warm dust relative to blue quasars and supporting a blow-out feedback phase.
Multimessenger observations and one-zone leptohadronic modeling of PKS 1725+123 during a flare constrain its emission to external Compton gamma-rays, SSC X-rays, and a neutrino rate of about 0.3 events per year peaking at 1 PeV.
J1105+1452 transitioned to a megahertz peaked-spectrum source with a new compact jet of radius ~0.68 pc, apparent velocity ~0.64c, and Doppler factor ~12, while X-ray emission stayed disk-corona dominated.
A changing-look AGN exhibits a rapid accretion-driven spectral transition with broad-line region temperatures of approximately 11,800 K measured via Boltzmann plots and stable black hole mass estimates of 5 times 10 to the 7 solar masses across epochs.
A lens model from Gaia DR3 and HST data combined with a Bayesian test on Chandra observations constrains the X-ray emission origin in lensed quasar J0659 to a 0.020 × 0.010 arcsec ellipse offset 0.014 arcsec from the optical source at 1σ.
Tentative double Gaussian excess at 1.59 GeV (2.6σ) and 11.15 GeV (3.7σ) in Fermi-LAT spectrum of blazar 4FGL J0604.9-0000, combined TS ≃ 27 (~4.3σ local).
This paper derives quantitative correction factors for traditional SSA minimum energy estimates to account for inhomogeneity and non-spherical geometry in emitting regions.
Low-luminosity AGN exhibit structure function slopes rising from 0.1 to 0.3 with black hole mass, no breaks on decadal scales, amplitude anticorrelated with luminosity and positively correlated with mass.
Detection of a persistent ~433-day optical QPO in blazar 3C 454.3 at 2.53σ significance using Lomb-Scargle, WWZ, and PDM methods, with a new test for seasonal gaps.
Lya nebulae around unobscured quasars are more extended, asymmetric, and show steeper velocity dispersion declines than those around obscured quasars, supporting an evolutionary AGN model at cosmic noon.
A criterion of |Δg| > 0.4 mag and |Δ(g-r)| > 0.2 mag detects photometric CL-AGN transitions in 9.6% of known hosts with 1.6% false positive rate from simulations.
SPENDER autoencoder plus k-d tree nearest-neighbor classification on DESI spectra identifies AGN and broad-line AGN at accuracies 0.952 and 0.965, recovering sources missed by single-line diagnostics.
A leptonic jet model with stochastic turbulent acceleration predicts hard and soft X-ray Fourier lags plus a transition regime in HBLs, with STA and nonlinear SSC cooling amplifying lags and explaining trends with flare duration.
JWST prism spectroscopy of 200 massive galaxies at z~3-15 shows normal star-forming galaxies dominate at z>6 while dusty systems and quiescent galaxies increase at lower redshift, with evidence for multiple quenching pathways.
Simulations demonstrate that a retrograde IMBH with mass ratio ~0.67 to the disc mass fragments a stellar disc into inner, misaligned, and outer components within 10-20 Myr.
Presents a public spectroscopic atlas of 887 Southern broad-line AGNs at low redshift, including continuum decompositions and emission-line fits.
Biconical disk-wind models show that small acceleration length R_v plus high terminal velocity is required to produce detached blueshifted CIV absorption in synthetic spectra at intermediate inclinations.
Seyfert 2 galaxies show detectable optical variability, enabling estimates of scattering region sizes consistent with the obscuring torus via amplitude matching to Seyfert 1s.
citing papers explorer
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The WISSHFUL program: the highest redshift UFO discovered in a non-lensed QSO
Detection of a variable stratified UFO with velocities 0.1c and 0.3c, extreme mass outflow rates, and kinetic powers of 1-10% of bolometric luminosity in quasar WISSH13 at z=3.294.
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A magnetically-supported disk-corona model for Changing-Look AGN transitions
Magnetized disk models lower the thermal-viscous instability threshold to Eddington ratios of 0.01-0.03 and yield limit-cycle timescales of months to years, jointly matching observations in five CLAGN only when the inner disk is strongly magnetized.
-
On the maximum neutrino flux of blazars in the one-zone leptohadronic model
An analytical derivation of maximum neutrino flux in the one-zone leptohadronic model shows predicted fluxes remain below IceCube levels for neutrino-candidate blazars.
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SDSS-V: Revealing a weak accretion state in X-ray selected red quasars
Red quasars are intrinsically X-ray weak with low alpha_OX values, tracing a distinct evolutionary stage of suppressed black hole accretion relative to stellar mass growth.
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Advance warning of $\gamma$-ray blazar flares from \textit{Fermi}-LAT light curves: a strictly causal machine-learning backtest
A causal machine-learning model using variability features from Fermi-LAT light curves predicts blazar flare activity within 90 days with 86% recall on held-out data for one FSRQ.
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The study of the circumnuclear environment of accreting supermassive black holes with realistic X-ray spectral models
New publicly available X-ray table models RXToPo and RXagn1 with realistic AGN geometries (torus, polar cone, disk, BLR) generated via RefleX and tested on NGC 424.
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Hidden Monsters with SPHEREx I: A goldmine for heavily reddened quasars at cosmic noon
Confirmation of 77 new heavily reddened quasars at 1.5 < z < 3.9 with high luminosities and extinctions, showing they are deficient in hot and warm dust relative to blue quasars and supporting a blow-out feedback phase.
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Zooming in on the GeV $\gamma$-ray flare of the blazar PKS 1725+123 with a multimessenger lens
Multimessenger observations and one-zone leptohadronic modeling of PKS 1725+123 during a flare constrain its emission to external Compton gamma-rays, SSC X-rays, and a neutrino rate of about 0.3 events per year peaking at 1 PeV.
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A Radio Changing-state Jet in the Narrow-line Seyfert 1 Galaxy J1105+1452
J1105+1452 transitioned to a megahertz peaked-spectrum source with a new compact jet of radius ~0.68 pc, apparent velocity ~0.64c, and Doppler factor ~12, while X-ray emission stayed disk-corona dominated.
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Tracing Active Galactic Nuclei Properties Through a Changing-look Event
A changing-look AGN exhibits a rapid accretion-driven spectral transition with broad-line region temperatures of approximately 11,800 K measured via Boltzmann plots and stable black hole mass estimates of 5 times 10 to the 7 solar masses across epochs.
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Determining the spatial origin of X-ray and optical emission in the $z = 3.1$ strongly lensed radio-quiet quasar GraL J065904.1+162909 to hundreds of parsecs
A lens model from Gaia DR3 and HST data combined with a Bayesian test on Chandra observations constrains the X-ray emission origin in lensed quasar J0659 to a 0.020 × 0.010 arcsec ellipse offset 0.014 arcsec from the optical source at 1σ.
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A Tentative Double Excess in the Gamma-Ray Spectrum of the Fermi Blazar 4FGL J0604.9-0000
Tentative double Gaussian excess at 1.59 GeV (2.6σ) and 11.15 GeV (3.7σ) in Fermi-LAT spectrum of blazar 4FGL J0604.9-0000, combined TS ≃ 27 (~4.3σ local).
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Towards improved synchrotron self absorption energy estimates: accounting for inhomogeneous and non-spherical emitting regions
This paper derives quantitative correction factors for traditional SSA minimum energy estimates to account for inhomogeneity and non-spherical geometry in emitting regions.
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Optical Variability Structure Function of Low-Luminosity AGN using ATLAS Lightcurves
Low-luminosity AGN exhibit structure function slopes rising from 0.1 to 0.3 with black hole mass, no breaks on decadal scales, amplitude anticorrelated with luminosity and positively correlated with mass.
-
Detection of optical quasi-periodic oscillation in the blazar 3C 454.3
Detection of a persistent ~433-day optical QPO in blazar 3C 454.3 at 2.53σ significance using Lomb-Scargle, WWZ, and PDM methods, with a new test for seasonal gaps.
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Constraining the nature of active galactic nuclei through circumgalactic Lya emission at z=2-3
Lya nebulae around unobscured quasars are more extended, asymmetric, and show steeper velocity dispersion declines than those around obscured quasars, supporting an evolutionary AGN model at cosmic noon.
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Identifying Changing-Look AGN Transitions in Light Curve Data with the Zwicky Transient Facility
A criterion of |Δg| > 0.4 mag and |Δ(g-r)| > 0.2 mag detects photometric CL-AGN transitions in 9.6% of known hosts with 1.6% false positive rate from simulations.
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Beyond traditional emission-line diagnostics: using autoencoders to uncover active galactic nuclei in DESI spectra
SPENDER autoencoder plus k-d tree nearest-neighbor classification on DESI spectra identifies AGN and broad-line AGN at accuracies 0.952 and 0.965, recovering sources missed by single-line diagnostics.
-
X-ray Fourier lag-frequency spectra modulated by stochastic turbulent acceleration in the jets of high-frequency-peaked BL Lac
A leptonic jet model with stochastic turbulent acceleration predicts hard and soft X-ray Fourier lags plus a transition regime in HBLs, with STA and nonlinear SSC cooling amplifying lags and explaining trends with flare duration.
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A Census of the 200 Most Massive Galaxies Spectroscopically Observed with JWST at zspec $\sim$3-15
JWST prism spectroscopy of 200 massive galaxies at z~3-15 shows normal star-forming galaxies dominate at z>6 while dusty systems and quiescent galaxies increase at lower redshift, with evidence for multiple quenching pathways.
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Stellar discs and intermediate-mass black holes in galactic nuclei I. Fragmenting the disc in an isotropic stellar potential
Simulations demonstrate that a retrograde IMBH with mass ratio ~0.67 to the disc mass fragments a stellar disc into inner, misaligned, and outer components within 10-20 Myr.
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OzSSy1: The Australian Southern Seyfert-1 Spectroscopic Atlas and Catalogue at z < 0.1
Presents a public spectroscopic atlas of 887 Southern broad-line AGNs at low redshift, including continuum decompositions and emission-line fits.
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Wind Acceleration as a Driver of Detached Blueshifted Absorption in Quasar Disk Winds
Biconical disk-wind models show that small acceleration length R_v plus high terminal velocity is required to produce detached blueshifted CIV absorption in synthetic spectra at intermediate inclinations.
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Detection of Variability in Seyfert 2 Galaxies and Measurement of the Optical Scattering Region Size
Seyfert 2 galaxies show detectable optical variability, enabling estimates of scattering region sizes consistent with the obscuring torus via amplitude matching to Seyfert 1s.
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Simulations of interaction between outflow and surrounding broken power-law circumnuclear medium: implications for different radio light curves of TDEs
3D hydro simulations show that TDE outflow interactions with a broken power-law CNM can reproduce the range of observed radio light curves via early flares inside the Bondi radius and possible late rebrightenings outside it.
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Morphology of Optical Changing-Look AGN-host Galaxies: Evidence for an Important Role of Mergers
CL-AGN host galaxies exhibit a 29% merger fraction (about 2x higher than non-CL-AGN controls) with morphology indicating modest disturbances, based on non-parametric metrics and visual inspection of DESI images.
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The Delta Resonance in the Neutrino Sky
A proton spectrum with index -3.1 interacting with 0.3 keV X-rays via the Delta resonance reproduces the observed 30 TeV neutrino break and limits the accompanying gamma-ray cascade contribution to ~10% of the isotropic background at 3 GeV.
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A Weak Fe K$\beta$ Emission Line in the Broad-Line Radio Galaxy 3C 111 Observed with XRISM: An Ionized Wind Absorption Feature?
XRISM observation of 3C 111 finds weak Fe Kβ possibly caused by blueshifted absorption from an ionized wind at 4600 or 17200 km/s, with kinetic power 10^41-10^44 erg/s smaller than the jet power.
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The exceptional 2017 gamma-ray flare of the radio galaxy NGC 1275: VERITAS and Multiwavelength Observations
New VERITAS observations of the 2017 VHE flare from NGC 1275, with multiwavelength SEDs, support a two-component blob-in-jet model placing gamma-ray emission near the C3 radio component at a 10-degree viewing angle.
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Exploring the Transitional Parameter Space of Blazars using Gamma-ray and X-ray Population Diagnostics
Changing-look blazars occupy intermediate regions in gamma-ray and X-ray parameter spaces but lie statistically closer to flat-spectrum radio quasars than to BL Lac objects according to centroids, PCA, UMAP, and random-forest classification.
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Halo-driven Origin and Suppression of Over-massive Black Holes and Little Red Dots
Halo-driven transient rapid growth followed by thermodynamic suppression explains over-massive black holes and Little Red Dots as precursors to standard SMBH-galaxy coevolution.
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The January 2010 flare of Mrk421: Insights from a stochastic acceleration model
The January 2010 flare of Mrk421 shows spectral variability consistent with stochastic acceleration, including development of a Maxwellian pile-up component in the particle distribution on three nights.
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HI 21-cm absorption in low- and high-excitation radio-loud AGNs at $z<0.5$ from MALS
Five new HI 21-cm absorption detections in LERGs and HERGs at z<0.5 reveal disturbed gas kinematics with velocity offsets over 350 km/s and a 3% detection rate consistent with lower-redshift samples.
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A universal relationship between the variability timescale and black hole mass in black hole jetted and non-jetted accreting systems
Mass-scaled DRW damping timescales in AGNs follow a linear relation with black hole mass (slope 0.35-0.50) for both jetted and non-jetted sources, supporting universal accretion physics.
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A Census of Variable Radio Sources at $3\,$GHz
A census of ~3600 variable compact radio sources at 3 GHz from VLASS epochs 1 and 2, with 5-9% showing >30% flux changes above 20-300 mJy and most consistent with blazars or quasars.
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A Systematic Search for Active Galactic Nucleus Flares in ZTF Data Release 23
Systematic search of ZTF DR23 data yields catalogs of 28,504 coarse and 1,984 refined AGN flares with public release.
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X-ray Spectral Properties of Four Classical TeV Blazars using Simultaneous Observations from NICER and NuSTAR
Simultaneous NICER+NuSTAR spectra of four TeV blazars show that 6 spectra require a blackbody component interpreted as accretion disk emission during low-flux states, plus Gaussian features at 1.4–1.7 keV in Mrk 421.
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Detection of Quasiperiodic Oscillations in the Blazar PKS 0735+178 with TESS
A transient ~11.2-hour optical QPO is detected in blazar PKS 0735+178 at 3-4 sigma significance using TESS sectors 71-72.
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Direct VLBI evidence for a buried AGN in the triple-merger LIRG UGC 2369S
VLBI imaging detects a compact radio source with Tb > 10^7 K and flat spectrum in the northern core of UGC 2369S, confirming a buried low-luminosity AGN.
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A Rare Gamma-ray Flaring episode of the Narrow-Line Seyfert 1 Galaxy 1H 0323+342
Multi-wavelength monitoring of a gamma-ray flare in 1H 0323+342 reveals sub-hour variability, jet-corona transition, and ~10^46 erg/s jet power via external Compton modeling of disk and BLR photons.
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The Fundamental Planes of Black Hole Activity for High-Synchrotron-Peaked BL Lacertae Objects
A sample of 69 HBLs yields intrinsic radio-X-ray correlation L_R,int ∝ L_X,int^0.68 and fundamental plane log L_R,int = 0.57 log L_X,int + 0.33 log M_BH + 12.65, consistent with synchrotron cooling model for X-ray emission.
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Limits on primordial black holes from the extragalactic gamma-ray background; current status and future projections
Sets upper limits on primordial black hole dark matter fraction using extragalactic gamma-ray background, claiming these are the tightest indirect constraints for the mass range.
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Constraining Orbital Eccentricity of a Supermassive Black Hole Binary Candidate PKS 2131-0211
Bayesian fitting of an eccentric Keplerian orbit to the radio light curve of PKS 2131-021 gives e = 0.053 ± 0.015 without red noise but favors a circular orbit plus DRW noise with e < 0.15.
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Changing-look Active Galactic Nuclei from SDSS, LAMOST and DESI Survey
Multi-epoch spectroscopic cross-matching yields 45 CLAGNs (43 turn-off, 2 turn-on) including 12 repeating sources that trace a high-low-high accretion-state path in the black-hole mass versus Eddington-ratio plane.
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FR0 radio galaxy jets -- I. linking jet dynamics and high-energy emission in LEDA 55267 and LEDA 58287
3D RHD simulations of FR0 jets in LEDA 55267 and LEDA 58287 show recollimation shocks driving compactness via turbulence and deceleration, with SED modeling predicting lepto-hadronic emission at TeV energies as a testable forecast.
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Taking Inventory of the Most Promising Lensed Radio Sources for Constraining Fundamental Properties of Dark Matter
Reports results from two searches for new radio lenses in existing surveys and discusses the completeness of the population usable for constraining dark matter properties via astrometric perturbations.
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Chasing the neutrino blazar candidates II: SED modeling with hadronic model
Hadronic SED modeling of 103 blazar candidates predicts proton synchrotron peaks in the MeV band for 99 sources and maximum neutrino fluxes detectable by up to 62 sources with next-generation telescopes.
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Spectro-Polarimetric Observations of TeV Sources (SPOTS): First results
First results from the SPOTS campaign reveal low average optical polarization (≲10%) and low magnetic field ordering (F_B ≲0.10) across 14 TeV blazars, with stochastic or rotating polarization angles and wavelength-dependent behavior indicating complex, turbulent jet structures.
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Detectability of Polarized Gamma-ray Emission from Blazar Flares with COSI
Estimates based on 17 years of Fermi LAT data indicate COSI may detect MeV polarization in a small number of blazar flares, with flat-spectrum radio quasars as the top targets.
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Indication of gamma-Ray Quasi-periodicity in GB6 J1037+5711 from Multi-technique Timing Analysis
Multi-technique timing analysis indicates a ~478-day QPO in the gamma-ray emission of BL Lac GB6 J1037+5711.