A Spectropolarimetric Test of the Structure of the Intrinsic Absorbers in the Quasar HS1603+3820

Abstract

We report the results of a spectropolarimetric observation of the C IV mini-BAL in the quasar HS1603+3820. The observations were carried out with the FOCAS instrument on the Subaru telescope and yielded an extremely high polarization sensitivity of 0.1%, at a resolving power of 1500. HS1603+3820 has been the target of a high-resolution spectroscopic monitoring campaign for more than four years, aimed at studying its highly variable C IV mini-BAL profile. Using the monitoring observations, in an earlier paper we were able to narrow down the causes of the variability to the following two scenarios: (1) scattering material of variable optical depth redirecting photons around the absorber, and (2) a variable, highly-ionized screen between the continuum source and the absorber which modulates the UV continuum incident on the absorber. The observations presented here provide a crucial test of the scattering scenario and lead us to disfavor it because (a) the polarization level is very small (p~0.6%) throughout the spectrum, and (b) the polarization level does not increase across the mini-BAL trough. Thus, the variable screen scenario emerges as our favored explanation of the C IV mini-BAL variability. Our conclusion is bolstered by recent X-ray observations of nearby mini-BAL quasars, which show a rapidly variable soft X-ray continuum that appears to be the result of transmission through an ionized absorber of variable ionization parameter and optical depth.

To appear in the Astrophysical Journal, vol. 719, August 2010

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• The Quasar Outflow Contribution to AGN Feedback: VLT Measurements of SDSS J0318-0600
• A Census of Intrinsic Narrow Absorption Lines in the Spectra of Quasars at z=2-4
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Cited by in corpus (8)

• Extreme-Velocity Quasar Outflows and the Role of X-ray Shielding
• Variable X-ray absorption in the mini-BAL QSO PG 1126-041
• Monitoring the Variability of Intrinsic Absorption Lines in Quasar Spectra
• The Sloan Digital Sky Survey Reverberation Mapping Project: Systematic Investigations of Short-Timescale CIV Broad Absorption Line Variability
• Multi-Sightline Observation of Narrow Absorption Lines in Lensed Quasar SDSS J1029+2623
• A Catalog of High-Velocity CIV Mini-BALs in the VLT-UVES and Keck-HIRES Archives
• Optical Variability Properties of Mini-BAL and NAL Quasars
• Coordinated X-ray and UV absorption within the accretion disk wind of the active galactic nucleus PG 1126-041