The buried Balmer-edge signatures from quasars

Abstract

In our previous paper, we have reported the detection of a Balmer edge absorption feature in the polarized flux of one quasar (Ton 202). We have now found similar Balmer edge features in the polarized flux of four more quasars (4C09.72, 3C95, B2 1208+32, 3C323.1), and possibly a few more, out of 14 newly observed with the VLT and Keck telescopes. In addition, we also re-observed Ton 202, but we did not detect such a dramatic feature, apparently due to polarization variability (the two observations are one-year apart). The polarization measurements of some quasars are affected by an interstellar polarization in our Galaxy, but the measurements have been corrected for this effect reasonably well. Since the broad emission lines are essentially unpolarized and the polarization is confined only to the continuum in the five quasars including Ton 202 in both epochs, the polarized flux is considered to originate interior to the broad emission line region. The Balmer edge feature seen in the polarized flux is most simply interpreted as an intrinsic spectral feature of the quasar UV/optical continuum, or the ``Big Blue Bump'' emission. In this case, the edge feature seen in absorption indeed indicates the thermal and optically-thick nature of the continuum emitted. However, we also discuss other possible interpretations.

arXiv commentAccepted for publication in MNRAS; 31 pages, 38 figures with reduced resolutions; the paper with a full resolution is at http://www.roe.ac.uk/~mk/papers/04Ba_vk.ps.gz

References in corpus (20)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• The Rest-Frame Extreme Ultraviolet Spectral Properties of QSOs
• The Soft X-Ray Properties of a Complete Sample of Optically Selected Quasars II. Final Results
• 9286 Stars: An Agglomeration of Stellar Polarization Catalogs
• A Composite HST Spectrum of Quasars
• Seyferts on the edge: polar scattering and orientation-dependent polarization in Seyfert 1 nuclei
• Non-LTE Models and Theoretical Spectra of Accretion Disks in Active Galactic Nuclei. III. Integrated Spectra for Hydrogen-Helium Disks
• Conference Summary: AGN Physics with the Sloan Digital Sky Survey
• A Spectropolarimetric Atlas of Seyfert 1 Galaxies
• AN IMPROVED MEASURE OF QUASAR ORIENTATION
• Polarimetry and Unification of Low-Redshift Radio Galaxies
• Discovery of a Classic FR-II Broad Absorption Line Quasar from the FIRST Survey
• Non-LTE, Relativistic Accretion Disk Fits to 3C~273 and the Origin of the Lyman Limit Spectral Break
• The Ultraviolet Peak of the Energy Distribution in 3C~273: Evidence for an Accretion Disk and Hot Corona Around a Massive Black Hole
• PKS 1004+13: A High-Inclination, Highly-Absorbed Radio-Loud QSO -- The First Radio-Loud BAL QSO at Low Redshift?
• Polarization from magnetized accretion discs: II. The effects of absorption opacity on Faraday rotation
• Optical Polarization of 52 Radio-Loud QSOs and BL Lac Objects
• A First Close Look at the Balmer-edge Behavior of the Quasar Big Blue Bump
• The Twice-Overlooked, Second FR II Broad Absorption Line Quasar LBQS 1138-0126
• Evidence for Polarized Synchrotron Components in Radio-Optical Aligned Quasars

Cited by in corpus (25)

• Space Telescope and Optical Reverberation Mapping Project. III. Optical Continuum Emission and Broad-Band Time Delays in NGC 5548
• Mapping extreme-scale alignments of quasar polarization vectors
• Global Radiation Magneto-hydrodynamic Simulations of Sub-Eddington Accretion Disks around Supermassive Black Holes
• Mapping the radial structure of AGN tori
• The characteristic blue spectra of accretion disks in quasars as uncovered in the infrared
• The UV Continuum of Quasars: Models and SDSS Spectral Slopes
• Cold Accretion Disks and Lineless Quasars
• Continuum Reverberation Mapping of the Accretion Disks in Two Seyfert 1 Galaxies
• Variability in Spectropolarimetric properties of Sy 1.5 galaxy Mrk 6
• Discovery of Polarization Reverberation in NGC 4151
• The dust-eliminated shape of quasar spectra in the near-infrared: a hidden part of the big blue bump
• A structure for quasars under the scope of polarisation I. The UV/optical polarisation dichotomy of type-1 and type-2 AGN
• Spectropolarimetry of low redshift Quasars: origin of the polarization and implications for black hole mass estimates
• Spectropolarimetric monitoring of active galaxy 3C390.3 with 6m telescope SAO RAS in the period 2009-2014
• A panchromatic review of thermal and nonthermal active galactic nuclei
• Blue, Green, and Red Bumps in AGN
• The polarized spectral energy distribution of NGC 4151
• Spectroscopy and polarimetry of the gravitationally lensed quasar Q0957+561
• Astrophysics in 2005
• Optical Spectropolarimetric Variability Properties in Blazars PKS 0637-75 and PKS 1510-089
• The relationship between variable and polarized optical spectral components of luminous type 1 non-blazar quasars
• Fluctuations of the intergalactic ionization field at redshift z ~ 2
• AGN accretion disks as spatially resolved by polarimetry
• Quasars' Optical Polarization and Balmer Edge Feature Revealed by Ultra-Violet, and Polarized Visible to Near Infrared Emissions
• Constraints on the optical polarization source in the luminous non-blazar quasar 3C 323.1 (PG 1545+210) from the photometric and polarimetric variability