Temperature Profiles of Accretion Disks in Luminous Active Galactic Nuclei derived from Ultraviolet Spectroscopic Variability

Abstract

The characteristic timescale ($\tau$) of continuum variability of the accretion disk in active galactic nuclei (AGNs) is known to be related to the thermal timescale, which is predicted to scale with AGN luminosity ($L$) and restframe wavelength (${\lambda }_{\mathrm{RF}}$) as $t_{\mathrm{th}}\propto L^{0.5}{\lambda }_{\mathrm{RF}}^2$ in the standard disk model. Using multi-epoch spectroscopic data from the Sloan Digital Sky Survey Reverberation Mapping project, we construct ultraviolet ensemble structure functions of luminous AGNs as a function of their luminosity and wavelength. Assuming that AGNs exhibit a single universal structure function when $\Delta t$ is normalized by $\tau$, wherein $\tau \propto L^a{\lambda }_{\mathrm{RF}}^b$, we find $a=0.50\pm 0.03$ and $b=1.42\pm 0.09$. While the value of $a$ aligns with the prediction from the standard disk model, $b$ is significantly smaller than expected, suggesting that the radial temperature (color) profile of the accretion disk is significantly steeper (shallower) than the standard disk model. Notably, this discrepancy with theory has been observed in previous studies based on spectroscopic reverberation mapping and gravitational microlensing. Although no current model of accretion disks fully matches our results, our findings provide valuable constraints for testing future physical models.

arXiv comment8 pages, 3 figures; accepted for publication in Astronomy & Astrophysics

References in corpus (68)

• A Relationship Between Nuclear Black Hole Mass and Galaxy Velocity Dispersion
• Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation-Mapping Database
• Hot Accretion Flows Around Black Holes
• A Catalog of Quasar Properties from SDSS DR7
• 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
• Nuclear Activity in Nearby Galaxies
• Estimating Black Hole Masses in Active Galaxies Using the Halpha Emission Line
• Are the Variations in Quasar Optical Flux Driven by Thermal Fluctuations?
• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• The Ensemble Photometric Variability of ~25000 Quasars in the Sloan Digital Sky Survey
• The Quasar Accretion Disk Size - Black Hole Mass Relation
• The Quasar Accretion Disk Size -- Black Hole Mass Relation
• Space Telescope and Optical Reverberation Mapping Project. III. Optical Continuum Emission and Broad-Band Time Delays in NGC 5548
• Magnetic Stress at the Marginally Stable Orbit: Altered Disk Structure, Radiation, and Black Hole Spin Evolution
• Black Hole Growth to z = 2 - I: Improved Virial Methods for Measuring M_BH and L/L_Edd
• Sizes and Temperature Profiles of Quasar Accretion Disks from Chromatic Microlensing
• The Sloan Digital Sky Survey Reverberation Mapping Project: Technical Overview
• The Sloan Digital Sky Survey Reverberation Mapping Project: Sample Characterization
• Swift monitoring of NGC 5548: X-ray reprocessing and short term UV/optical variability
• A characteristic optical variability timescale in astrophysical accretion disks
• Accretion disk reverberation with Hubble Space Telescope observations of NGC 4593: evidence for diffuse continuum lags
• On the use of structure functions to study blazar variability: caveats and problems
• The Spatial Structure of An Accretion Disk
• Revisiting Stochastic Variability of AGNs with Structure Functions
• Microlensing variability in the gravitationally lensed quasar QSO 2237+0305 = the Einstein Cross. II. Energy profile of the accretion disk
• The origin of the UV/optical lags in NGC 5548
• X-ray/UV/optical variability of NGC 4593 with Swift: Reprocessing of X-rays by an extended reprocessor
• Super-Eddington accretion disc around a Kerr black hole
• The Sloan Digital Sky Survey Reverberation Mapping Project: No Evidence for Evolution in the M-sigma Relation to z~1
• Optical variability of AGN in the PTF/iPTF survey
• Self-shadowing Effects of Slim Accretion Disks in Active Galactic Nuclei: Diverse Appearance of the Broad-line Region
• The Sloan Digital Sky Survey Reverberation Mapping Project: Initial CIV Lag Results from Four Years of Data
• The Sloan Digital Sky Survey Stripe 82 Imaging Data: Depth-Optimized Co-adds Over 300 Deg^2 in Five Filters
• Limitations on the recovery of the true AGN variability parameters using Damped Random Walk modeling
• Quantifying the impact of variable BLR diffuse continuum contributions on measured continuum inter-band delays
• Space Telescope and Optical Reverberation Mapping Project VI: reverberating Disk Models for NGC 5548
• Supermassive black holes with high accretion rates in active galactic nuclei. XI. Accretion disk reverberation mapping of Mrk 142
• The Average Size and Temperature Profile of Quasar Accretion Disks
• Detection of Time Lags Between Quasar Continuum Emission Bands based on Pan-STARRS Light-curves
• The Sloan Digital Sky Survey Reverberation Mapping Project: Accretion-Disk Sizes from Continuum Lags
• A Revised Calibration of the Virial Mass Estimator for Black Holes in Active Galaxies Based on Single-epoch H$\beta$ Spectra
• Optical Variability of Quasars with 20-Year Photometric Light Curves
• The accretion disc in the quasar SDSS J0924+0219
• The UV peak in Active Galactic Nuclei : a false continuum from blurred reflection ?
• Corona-Heated Accretion-disk Reprocessing (CHAR): A Physical Model to Decipher the Melody of AGN UV/optical Twinkling
• Quasar Black Hole Mass Estimates in the Era of Time Domain Astronomy
• Magellan Spectroscopy of Low-Redshift Active Galactic Nuclei
• The Sloan Digital Sky Survey Reverberation Mapping Project: Ensemble Spectroscopic Variability of Quasar Broad Emission Lines
• AGN Continuum Reverberation Mapping Based on Zwicky Transient Facility Light Curves
• A Study of Gravitational Lens Chromaticity using Ground-based Narrow Band Photometry
• Measuring Microlensing using Spectra of Multiply Lensed Quasars
• Improved Spectrophotometric Calibration of the SDSS-III BOSS Quasar Sample
• Near Infrared Variability of obscured and unobscured X-ray selected AGN in the COSMOS field
• Chandra Survey of Nearby Galaxies: A Significant Population of Candidate Central Black Holes in Late-type Galaxies
• How far is quasar UV/optical variability from damped random walk at low frequency?
• A hard look at thermal reverberation and optical/UV lags in NGC 5548
• Winds Can "Blow Up" AGN Accretion Disk Sizes
• Quasar Microlensing Variability Studies Favor Shallow Accretion Disk Temperature Profiles
• Rimmed and Rippled Accretion Disc Models to Explain AGN Continuum Lags
• The optical variability of SDSS quasars from multi-epoch spectroscopy. II. color variation
• Structure of the Accretion Disk in the Lensed Quasar Q2237+0305 from Multi-Epoch and Multi-Wavelength Narrow Band Photometry
• HST imaging of four gravitationally lensed quasars
• Reconciling the Quasar Microlensing Disc Size Problem with a Wind Model of Active Galactic Nucleus
• Universality in the Random Walk Structure Function of Luminous Quasi-Stellar Objects
• Ensemble power spectral density of SDSS quasars in UV/optical bands
• Black Hole Mass Estimation in Type 1 AGN: H$\beta$ vs. Mg II lines and the role of Balmer continuum
• Spectral shape corrections for SDSS BOSS quasars

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