The relationship between variable and polarized optical spectral components of luminous type 1 non-blazar quasars

Abstract

Optical spectropolarimetry carried out by Kishimoto et al. (2004) has shown that several luminous type 1 quasars show a strong decrease of the polarized continuum flux in the rest-frame near-UV wavelengths of $\lambda <4000$Å. In the literature, this spectral feature is interpreted as evidence of the broadened hydrogen Balmer absorption edge imprinted in the accretion disk thermal emission due to the disk atmospheric opacity effect. On the other hand, the quasar flux variability studies have shown that the variable continuum component in UV-optical spectra of quasars, which is considered to be a good indicator of the intrinsic spectral shape of the accretion disk emission, generally have significantly flat spectral shape throughout the near-UV to optical spectral range. To examine whether the disk continuum spectral shapes revealed as the polarized flux and as the variable component spectra are consistent with each other, we carry out multi-band photometric monitoring observations for a sample of four polarization-decreasing quasars of Kishimoto et al. (2004) (4C09.72, 3C323.1, Ton 202, and B2 1208+32) to derive the variable component spectra and compare the spectral shape of them with that of the polarized flux spectra. Contrary to expectation, we confirm that the two spectral components of these quasars have totally different spectral shape in that the variable component spectra are significantly bluer compared to the polarized flux spectra. This discrepancy in the spectral shape may imply either (1) the decrease of polarization degree in the rest-frame UV wavelengths is not indicating the Balmer absorption edge feature but is induced by some unknown (de)polarization mechanisms, or (2) the UV-optical flux variability is occurring preferentially at the hot inner radii of the accretion disk and thus the variable component spectra do not reflect the whole accretion disk emission.

12 pages, 5 figures and 3 tables, accepted for publication in Publications of the Astronomical Society of Japan (PASJ) 2016 April 13

References in corpus (18)

• The 2.5 m Telescope of the Sloan Digital Sky Survey
• A Systematic Search for Changing-Look Quasars in SDSS
• Space Telescope and Optical Reverberation Mapping Project. III. Optical Continuum Emission and Broad-Band Time Delays in NGC 5548
• Space Telescope and Optical Reverberation Mapping Project. II. Swift and HST Reverberation Mapping of the Accretion Disk of NGC 5548
• Testing thermal reprocessing in AGN accretion discs
• Reverberation Measurements of the Inner Radius of the Dust Torus in 17 Seyfert Galaxies
• The characteristic blue spectra of accretion disks in quasars as uncovered in the infrared
• Radio-loud Narrow Line Seyfert 1 under a different perspective: a revised black hole mass estimate from optical spectropolarimetry
• An accretion disc model for quasar optical variability
• The Discovery of Timescale-Dependent Color Variability of Quasars
• The Sloan Digital Sky Survey Reverberation Mapping Project: Ensemble Spectroscopic Variability of Quasar Broad Emission Lines
• Kiso Supernova Survey (KISS): Survey Strategy
• Multiple Regression Analysis of the Variable Component in the Near-Infrared Region for Type 1 AGN MCG+08-11-011
• Constraints on the temperature inhomogeneity in quasar accretion discs from the ultraviolet-optical spectral variability
• Spectropolarimetric monitoring of active galaxy 3C390.3 with 6m telescope SAO RAS in the period 2009-2014
• SALT long-slit spectroscopy of CTS C30.10: two-component Mg II line
• Polarization microlensing in the quadruply imaged broad absorption line quasar H1413+117
• The stability of the optical flux variation gradient for 3C120

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• Spectroscopy and polarimetry of the gravitationally lensed quasar SDSS J1004+4112 with the 6m SAO RAS telescope
• Constraints on accretion disk size in the massive type 1 quasar PG 2308+098 from optical continuum reverberation lags