@article{f8ef27d18b7c48c3967e4bea4ac9452d,
title = "Spectropolarimetry of high-redshift obscured and red quasars",
abstract = "Spectropolarimetry is a powerful technique that has provided critical support for the geometric unification model of local active galactic nuclei. In this paper, we present optical [rest-frame ultraviolet (UV)] Keck spectropolarimetry of five luminous obscured (type 2) and extremely red quasars (ERQs) at z ≃ 2.5. Three objects reach polarization fractions of ≳ 10 per cent in the continuum. We prefer dust scattering as the dominant scattering and polarization mechanism in our targets, though electron scattering cannot be completely excluded. Emission lines are polarized at a lower level than the continuum. This suggests that the emission-line region exists on similar spatial scales as the scattering region. In three objects, we detect an intriguing 90°swing in the polarization position angle as a function of line-of-sight velocity in the emission lines of Ly α, CIV, and NV. We interpret this phenomenon in the framework of a geometric model with an equatorial scattering region in which the scattering material is outflowing at several thousand km s-1. Our model explains several salient features of observations by scattering on scales of a few tens of pc. Our observations provide a tantalizing view of the inner region geometry and kinematics of high-redshift obscured and ERQs. Our data and modelling lend strong support for toroidal obscuration and powerful outflows on the scales of the UV emission line region, in addition to the larger scale outflows inferred previously from the optical emission line kinematics.",
keywords = "Polarization, Quasars: emission lines, Quasars: general, Scattering",
author = "Alexandroff, {Rachael M.} and Zakamska, {Nadia L.} and Barth, {Aaron J.} and Fred Hamann and Strauss, {Michael A.} and Julian Krolik and Greene, {Jenny E.} and Isabelle P{\^a}ris and Ross, {Nicholas P.}",
note = "Funding Information: Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. Funding Information: The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Funding Information: The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazillian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participartion Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, NewMexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, Yale University. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration We would like to thank the referee for many helpful comments and suggestions, the inclusion ofwhich helped to improve our paper. RMA would like to acknowledge the assistance of C. Steidel, A. Strom, D. Perley, and H. Tran during observations at Keck I and the assistance of M. Kassis on the evening of LRISp observations. RMA would also like to thank D. Neufeld for useful conversations and S. Veilleux for allowing us to adapt fig. 8 of Veilleux et al. (2016). NLZ would like to acknowledge the remote observing support of Yale University. RMA was supported in part by NASA JPL grant 1520456. Support for this work was provided in part by the National Aeronautics and Space Administration through Chandra Award Number GO6-17100X issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060. NLZ acknowledges support by the Catalyst award of the Johns Hopkins University. Research by AJB is supported in part by NSF grant AST-1412693. Funding Information: RMA was supported in part by NASA JPL grant 1520456. Support for this work was provided in part by the National Aeronautics and Space Administration through Chandra Award Number GO6-17100X issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060. NLZ acknowledges support by the Catalyst award of the Johns Hopkins University. Research by AJB is supported in part by NSF grant AST-1412693. Publisher Copyright: {\textcopyright} 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.",
year = "2018",
month = oct,
day = "1",
doi = "10.1093/mnras/sty1685",
language = "English (US)",
volume = "479",
pages = "4936--4957",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "4",
}