The ensemble broad-frequency power spectrum of Stripe-82 quasars from multiple surveys

Abstract

Variability is a striking features of quasars, observed at all timescales wavelengths. Studying its properties and the correlations with the physical parameters (e.g. black hole mass and accretion rate) provides significant insights into accretion physics. However, the detailed picture and the exact interplay between different emitting regions are not yet clear. We combine data from Sloan Digital Sky Survey (SDSS), the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1, PS1), the Zwicky Transient Facility (ZTF), and the Gaia space telescope to constrain the power spectrum of quasars in the Stripe-82 region over a broad frequency range, 10^{-1} to 10^{-3} day^{-1}(rest frame). Light curves are matched and cross-calibrated to reach \sim 20 years in the r-band for 4037 quasars. We split the sample into bins of the same black hole mass, accretion rate, and redshift, and measure the ensemble power spectral density (PSD) in each bin. The power spectra of SDSS, ZTF, and Gaia are measured independently. We do not measure it on PS1 data due to more erratic cadence, but we discuss the use of interpolation techniques, eventually allowing us to use the data together. We find significant evidence that the long-term UV/optical variability of quasars is stationary, as the ensemble PSD estimates from SDSS, Gaia and ZTF are consistent within the errors despite coming from different surveys and years. The PSD shape is consistent with a bending power law with spectral indices of -2.7 and -1 at high and low frequencies. A fit with the PSD associated with a damped random walk is significantly worse. The PSD amplitude below the break does not depend on black hole mass, but there is some evidence for anti-correlation with the accretion rate. The bending frequency, instead, scales with the black hole mass as ${\nu }_b$ \propto M_{\mathrm{BH}}^{-0.6\pm0.1} and does not depend on the accretion rate.

Accepted for publication on Astronomy&Astrophysics on Nov. 17

References in corpus (50)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• The NumPy array: a structure for efficient numerical computation
• The Gaia mission
• LSST: from Science Drivers to Reference Design and Anticipated Data Products
• The Zwicky Transient Facility: System Overview, Performance, and First Results
• A Catalog of Quasar Properties from SDSS DR7
• First Results from the Catalina Real-time Transient Survey
• The Zwicky Transient Facility: Data Processing, Products, and Archive
• ATLAS: A High-Cadence All-Sky Survey System
• The Palomar Transient Factory: System Overview, Performance and First Results
• Revisiting the Unified Model of Active Galactic Nuclei
• The Zwicky Transient Facility: Science Objectives
• 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
• Active Galactic Nuclei as scaled-up Galactic black holes
• The Pan-STARRS1 Database and Data Products
• Gaia broad band photometry
• Combined Long and Short Timescale X-ray Variability of NGC4051 with RXTE and XMM-Newton
• SDSS Standard Star Catalog for Stripe 82: the Dawn of Industrial 1% Optical Photometry
• A Description of Quasar Variability Measured Using Repeated SDSS and POSS Imaging
• Long-term optical variability properties of the Palomar-Green quasars
• Kepler Observations of Rapid Optical Variability in Active Galactic Nuclei
• Reverberation mapping of Active Galactic Nuclei: from X-ray corona to dusty torus
• A characteristic optical variability timescale in astrophysical accretion disks
• On the use of structure functions to study blazar variability: caveats and problems
• Optimal Time-Series Selection of Quasars
• Optimization of the Observing Cadence for the Rubin Observatory Legacy Survey of Space and Time: a pioneering process of community-focused experimental design
• Revisiting Stochastic Variability of AGNs with Structure Functions
• Limitations on the recovery of the true AGN variability parameters using Damped Random Walk modeling
• Improving Damped Random Walk parameters for SDSS Stripe 82 Quasars with Pan-STARRS1
• Corona-Heated Accretion-disk Reprocessing (CHAR): A Physical Model to Decipher the Melody of AGN UV/optical Twinkling
• Optical Variability of Quasars with 20-Year Photometric Light Curves
• Examining AGN UV/optical Variability Beyond the Simple Damped Random Walk
• How far is quasar UV/optical variability from damped random walk at low frequency?
• Deep modeling of quasar variability
• Optically variable active galactic nuclei in the 3 yr VST survey of the COSMOS field
• A structure function analysis of VST-COSMOS AGN
• The LSST era of supermassive black holes accretion-disk reverberation mapping
• A physical model for the UV/optical power spectra of AGN
• Gaia Data Release 3: The first Gaia catalogue of variable AGN
• Expectations for time-delay measurements in active galactic nuclei with the Vera Rubin Observatory
• Universality in the Random Walk Structure Function of Luminous Quasi-Stellar Objects
• Ensemble power spectral density of SDSS quasars in UV/optical bands
• The universal shape of the X-ray variability power spectrum of AGN up to $z\sim 3$
• On possible proxies of AGN light curves cadence selection in future time domain surveys
• Blazar variability with the Vera C. Rubin Legacy Survey of Space and Time (LSST)
• The X-ray variability of AGN: power-spectrum and variance analysis of the Swift/BAT light curves
• Selection of optically variable active galactic nuclei via a random forest algorithm
• Modelling variability power spectra of active galaxies from irregular time series
• High frequency breaks in optical active galactic nuclei power spectral density