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The first high-redshift changing-look quasars

Ross, Nicholas P. and Graham, Matthew J. and Calderone, Giorgio and Ford, K. E. Saavik and McKernan, Barry and Stern, Daniel (2020) The first high-redshift changing-look quasars. Monthly Notices of the Royal Astronomical Society, 498 (2). pp. 2339-2353. ISSN 0035-8711.

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We report on three redshift z > 2 quasars with dramatic changes in their C IV emission lines, the first sample of changing-look quasars (CLQs) at high redshift. This is also the first time the changing-look behaviour has been seen in a high-ionization emission line. SDSS J1205+3422, J1638+2827, and J2228 + 2201 show interesting behaviour in their observed optical light curves, and subsequent spectroscopy shows significant changes in the C IV broad emission line, with both line collapse and emergence being displayed on rest-frame time-scales of ∼240–1640 d. These are rapid changes, especially when considering virial black hole mass estimates of M_(BH) > 10⁹M⊙ for all three quasars. Continuum and emission line measurements from the three quasars show changes in the continuum-equivalent width plane with the CLQs seen to be on the edge of the full population distribution, and showing indications of an intrinsic Baldwin effect. We put these observations in context with recent state-change models, and note that even in their observed low-state, the C IV CLQs are generally above ∼5 per cent in Eddington luminosity.

Item Type:Article
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URLURL TypeDescription Paper ItemData/Code
Ross, Nicholas P.0000-0003-1830-6473
Graham, Matthew J.0000-0002-3168-0139
McKernan, Barry0000-0002-9726-0508
Stern, Daniel0000-0003-2686-9241
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 August 8. Received 2020 July 30; in original form 2020 February 1. Published: 02 September 2020. We thank: Andy Lawrence, Mike Hawkins and David Homan for useful discussion; the referee for a very constructive report that improved the paper; NPR acknowledges support from the STFC and the Ernest Rutherford Fellowship scheme. MJG is supported in part by the NSF grants AST-1815034, and the NASA grant 16-ADAP16-0232. This paper heavily used TOPCAT (v4.4) (Taylor 2005, 2011). This research made use of Astropy, a community-developed core Python package for Astronomy (Astropy Collaboration 2013; The Astropy Collaboration 2018). pylustrator (Gerum 2019) was also used. 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 SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation 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, New Mexico 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, and Yale University. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, and NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology. WISE and NEOWISE are funded by the National Aeronautics and Space Administration. Based on observations obtained with the Samuel Oschin 48-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. NPR dedicates this work, and indeed his previous research, to his father. Dad had a deep love for science, mathematics, and questioning the conventional wisdom. His support allowed me to become an astrophysicist and to have the adventures and discoveries we did. He is sorely missed.
Group:Infrared Processing and Analysis Center (IPAC), Zwicky Transient Facility
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Participating InstitutionsUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
ZTF partner institutionsUNSPECIFIED
Subject Keywords:accretion, accretion discs – surveys – quasars: general – quasars: individual (SDSS J120544.7+342252.4, SDSS J163852.9+28270.7.7, SDSS J222818.7 + 220102.9)
Issue or Number:2
Record Number:CaltechAUTHORS:20201214-092957256
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Official Citation:Nicholas P Ross, Matthew J Graham, Giorgio Calderone, K E Saavik Ford, Barry McKernan, Daniel Stern, The first high-redshift changing-look quasars, Monthly Notices of the Royal Astronomical Society, Volume 498, Issue 2, October 2020, Pages 2339–2353,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107060
Deposited By: Tony Diaz
Deposited On:14 Dec 2020 20:50
Last Modified:05 Feb 2021 20:09

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