TY - JOUR
T1 - The Time Domain Spectroscopic Survey
T2 - Changing-look Quasar Candidates from Multi-epoch Spectroscopy in SDSS-IV
AU - Green, Paul J.
AU - Pulgarin-Duque, Lina
AU - Anderson, Scott F.
AU - MacLeod, Chelsea L.
AU - Eracleous, Michael
AU - Ruan, John J.
AU - Runnoe, Jessie
AU - Graham, Matthew
AU - Roulston, Benjamin R.
AU - Schneider, Donald P.
AU - Ahlf, Austin
AU - Bizyaev, Dmitry
AU - Brownstein, Joel R.
AU - Del Casal, Sonia Joesephine
AU - Dodd, Sierra A.
AU - Hoover, Daniel
AU - Matt, Cayenne
AU - Merloni, Andrea
AU - Pan, Kaike
AU - Ramirez, Arnulfo
AU - Ridder, Margaret
N1 - Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.
PY - 2022/7/1
Y1 - 2022/7/1
N2 - Active galactic nuclei (AGN) can vary significantly in their rest-frame optical/UV continuum emission, and with strong associated changes in broad line emission, on much shorter timescales than predicted by standard models of accretion disks around supermassive black holes. Most such changing-look or changing-state AGN - and at higher luminosities, changing-look quasars (CLQs) - have been found via spectroscopic follow-up of known quasars showing strong photometric variability. The Time Domain Spectroscopic Survey of the Sloan Digital Sky Survey IV (SDSS-IV) includes repeat spectroscopy of large numbers of previously known quasars, many selected irrespective of photometric variability, and with spectral epochs separated by months to decades. Our visual examination of these repeat spectra for strong broad line variability yielded 61 newly discovered CLQ candidates. We quantitatively compare spectral epochs to measure changes in continuum and Hβ broad line emission, finding 19 CLQs, of which 15 are newly recognized. The parent sample includes only broad line quasars, so our study tends to find objects that have dimmed, i.e., turn-off CLQs. However, we nevertheless find four turn-on CLQs that meet our criteria, albeit with broad lines in both dim and bright states. We study the response of Hβ and Mg ii emission lines to continuum changes. The Eddington ratios of CLQs are low, and/or their Hβ broad line width is large relative to the overall quasar population. Repeat quasar spectroscopy in the upcoming SDSS-V black hole Mapper program will reveal significant numbers of CLQs, enhancing our understanding of the frequency and duty cycle of such strong variability, and the physics and dynamics of the phenomenon.
AB - Active galactic nuclei (AGN) can vary significantly in their rest-frame optical/UV continuum emission, and with strong associated changes in broad line emission, on much shorter timescales than predicted by standard models of accretion disks around supermassive black holes. Most such changing-look or changing-state AGN - and at higher luminosities, changing-look quasars (CLQs) - have been found via spectroscopic follow-up of known quasars showing strong photometric variability. The Time Domain Spectroscopic Survey of the Sloan Digital Sky Survey IV (SDSS-IV) includes repeat spectroscopy of large numbers of previously known quasars, many selected irrespective of photometric variability, and with spectral epochs separated by months to decades. Our visual examination of these repeat spectra for strong broad line variability yielded 61 newly discovered CLQ candidates. We quantitatively compare spectral epochs to measure changes in continuum and Hβ broad line emission, finding 19 CLQs, of which 15 are newly recognized. The parent sample includes only broad line quasars, so our study tends to find objects that have dimmed, i.e., turn-off CLQs. However, we nevertheless find four turn-on CLQs that meet our criteria, albeit with broad lines in both dim and bright states. We study the response of Hβ and Mg ii emission lines to continuum changes. The Eddington ratios of CLQs are low, and/or their Hβ broad line width is large relative to the overall quasar population. Repeat quasar spectroscopy in the upcoming SDSS-V black hole Mapper program will reveal significant numbers of CLQs, enhancing our understanding of the frequency and duty cycle of such strong variability, and the physics and dynamics of the phenomenon.
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U2 - 10.3847/1538-4357/ac743f
DO - 10.3847/1538-4357/ac743f
M3 - Article
AN - SCOPUS:85134745484
SN - 0004-637X
VL - 933
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 180
ER -