Changing-look Quasar Candidates: First Results from Follow-up Spectroscopy of Highly Optically Variable Quasars
Year: 2019
Type: article
Abstract: Active galactic nuclei (AGNs) that show strong rest-frame optical/UV variability in their blue continuum and broad line emission are classified as changing-look AGN, or at higher luminosities, changing-look quasars (CLQs). These surprisingly large and sometimes rapid transitions challenge accepted models of quasar physics and duty cycles, offer several new avenues for study of quasar host galaxies, and open a wider interpretation of the cause of differences between broad and narrow-line AGN. To better characterize extreme quasar variability, we present follow-up spectroscopy as part of a comprehensive search for CLQs across the full Sloan Digital Sky Survey (SDSS) footprint using spectroscopically confirmed quasars from the SDSS DR7 catalog. Our primary selection requires large-amplitude ( mag, mag) variability over any of the available time baselines probed by the SDSS and Pan-STARRS 1 surveys. We employ photometry from the Catalina Sky Survey to verify variability behavior in CLQ candidates where available, and confirm CLQs using optical spectroscopy from the William Herschel, MMT, Magellan, and Palomar telescopes. For our adopted signal-to-noise ratio threshold on variability of broad Hβ emission, we find 17 new CLQs, yielding a confirmation rate of ≳20%. These candidates are at lower Eddington ratio relative to the overall quasar population, which supports a disk-wind model for the broad line region. Based on our sample, the CLQ fraction increases from 10% to roughly half as the continuum flux ratio between repeat spectra at 3420 Å increases from 1.5 to 6. We release a catalog of more than 200 highly variable candidates to facilitate future CLQ searches.
Source: The Astrophysical Journal
Authors: Chelsea L. MacLeod, Paul J. Green, Scott F. Anderson, Alastair Bruce, Michael Eracleous, Matthew Graham, David Homan, Andy Lawrence, Amy LeBleu, Nicholas P. Ross, John J. Ruan, Jessie Runnoe, Daniel Stern, William Burgett, Kenneth C. Chambers, Nick Kaiser, Eugene Magnier, Nigel Metcalfe
Institutions: Smithsonian Astrophysical Observatory, Center for Astrophysics Harvard & Smithsonian, University of Washington, Royal Observatory, Pennsylvania State University, California Institute of Technology, University of Central Florida, McGill University, University of Michigan, Jet Propulsion Laboratory, University of Hawaiʻi at Mānoa, École Normale Supérieure - PSL, Durham University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, Smithsonian Institution, U.S. Department of Energy, National Aeronautics and Space Administration, Alfred P. Sloan Foundation, Yale University, Vanderbilt University, Princeton University, Ohio State University, California Institute of Technology, Harvard University, University of Washington, Johns Hopkins University, University of Pittsburgh, Carnegie Mellon University, Case Western Reserve University, Drexel University, Universität Basel, University of Portsmouth, New Mexico State University, Space Telescope Science Institute, York University, Queen's University Belfast, Durham University, Chinese Academy of Sciences, Queen's University, Max-Planck-Gesellschaft, National Central University, Eötvös Loránd Tudományegyetem, Max-Planck-Institut für Astronomie, Office of Science, Jet Propulsion Laboratory, College of Engineering, Michigan State University, Smithsonian Astrophysical Observatory, Science Mission Directorate, Science and Technology Facilities Council, U.S. Naval Observatory, Planetary Science Division, Fermilab, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, Los Alamos National Laboratory
Awards: G1089842194, Collaborative Research: Accretion Revelations from Changing-Look Quasars, Open Exploration of the Time Domain with the Catalina Real-Time Transient Survey, The Catalina Real-Time Transient Survey (CRTS), A COMPREHENSIVE DUAL HEMISPHERE NEO SURVEY., G3727113875, G4474636675, G5808996516, G618131832, Travel support for Edinburgh PATT observers 2014-2016, A NEO SEARCH PROGRAM USING THE PAN-STARRS PS1 TELESCOPETHE GOAL OF THE PROPOSED RESEARCH IS TO USE T, G7187964967, Pan-STARRS1: Operations; Public Data Release; Education and Outreach, G7950275392, G833430883, Collaborative Research: Accretion Revelations from Changing-Look Quasars
OpenAlex ID: W2911381628