Reddening and the Shape of the Variable Component of the Continua of Active Galactic Nuclei From the Optical to the Far Ultraviolet. I

Abstract

We analyze the photometric variability of 4,611 active galactic nuclei (AGNs) from the Sloan Digital Sky Survey Stripe 82. We recover the spectral energy distribution (SED) of the variable flux as a function of wavelength. For rest wavelengths longer than $\sim \lambda 2200$ we find that the SED of the variable component of the bluest AGNs is consistent with the $F_{\nu }\propto {\nu }^{+1/3}$ spectrum predicted for an externally-illuminated accretion disc. We confirm there is some residual variable emission corresponding to the "small blue bump" and other broad-line region variability. We interpret steeper optical spectra of the variable component as being due to intrinsic reddening. This is supported by the correlation of the Balmer decrement with the colour excess of the variable component. We find the median internal reddening of SDSS AGNs in Stripe 82 with $z<0.4$ to be $E(B-V)\approx 0.10$ in agreement with the reddening derived from the Balmer decrement. Individual AGNs in the sample can have $E(B-V)>0.4$

arXiv comment9 pages, 5 figures. To appear in MNRAS. On-line supplementary material available on request from first author

References in corpus (24)

• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Quasar Sample
• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• SDSS Standard Star Catalog for Stripe 82: the Dawn of Industrial 1% Optical Photometry
• Testing thermal reprocessing in AGN accretion discs
• Broad-line Balmer Decrements in Blue Active Galactic Nuclei
• The correlations between optical variability and physical parameters of quasars in SDSS Stripe 82
• Variability selected high-redshift quasars on SDSS Stripe 82
• The Color Variability of Quasars
• Long-term IR Photometry of Seyferts
• Spectral variability of quasars from multi-epoch photometric data in the Sloan Digital Sky Survey Stripe 82
• The case for cases B and C: intrinsic hydrogen line ratios of the broad-line region of active galactic nuclei, reddenings, and accretion disc sizes
• Long-Term Optical Continuum Color Variability of Nearby Active Galactic Nuclei
• Assessment of stochastic and deterministic models of 6304 quasar lightcurves from SDSS Stripe 82
• Partial dust obscuration in active galactic nuclei as a cause of broad-line profile and lag variability, and apparent accretion disc inhomogeneities
• Statistical Properties of Multi-epoch Spectral Variability of SDSS Stripe82 Quasars
• Low redshift quasars in the SDSS Stripe 82. The host galaxies
• Near Infrared Photometric properties of 130,000 Quasars: An SDSS-UKIDSS matched catalog
• AGN Reddening and Ultraviolet Extinction Curves from Hubble Space Telescope Spectra
• On R-W1 as A Diagnostic to Discover Obscured Active Galactic Nuclei in Wide-Area X-ray Surveys
• Fe II emission in active galactic nuclei
• The relationship between X-ray and optical absorbers in active galactic nuclei
• The location of the dust causing internal reddening of active galactic nuclei
• Estimating Black Hole Masses in Hundreds of Quasars

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• Estimating reddening of the continuum and broad-line region of active galactic nuclei: the mean reddening of NGC 5548 and the size of the accretion disc
• The Host Galaxy Fluxes of Active Galaxy Nuclei Are Generally Overestimated by the Flux Variation Gradient Method