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Title: The Time Domain Spectroscopic Survey: Changing-look Quasar Candidates from Multi-epoch Spectroscopy in SDSS-IV

Journal Article · · The Astrophysical Journal
ORCiD logo [1];  [1];  [2]; ORCiD logo [3]; ORCiD logo [4]; ORCiD logo [5]; ORCiD logo [6]; ORCiD logo [7]; ORCiD logo [8]; ORCiD logo [4];  [2]; ORCiD logo [9]; ORCiD logo [10];  [2]; ORCiD logo [11];  [2];  [12];  [13]; ORCiD logo [14];  [2] more »;  [15]; ORCiD logo [16] « less
  1. Harvard & Smithsonian, Cambridge, MA (United States)
  2. University of Washington, Seattle, WA (United States)
  3. BlackSky, Seattle, WA (United States)
  4. Pennsylvania State University, University Park, PA (United States)
  5. Bishop's University, Sherbrooke, QC (Canada)
  6. Vanderbilt University, Nashville, TN (United States)
  7. California Institute of Technology (CalTech), Pasadena, CA (United States)
  8. Harvard & Smithsonian, Cambridge, MA (United States); Boston University, MA (United States)
  9. Apache Point Observatory and New Mexico State University, Sunset, NM (United States); Moscow State University (Russia)
  10. University of Utah, Salt Lake City, UT (United States)
  11. University of Washington, Seattle, WA (United States); University of California Santa Cruz, CA (United States)
  12. University of Washington, Seattle, WA (United States); University of Michigan, Ann Arbor, MI (United States)
  13. Max-Planck-Institut für extraterrestrische Physik (MPE), Garching (Germany)
  14. Apache Point Observatory and New Mexico State University, Sunset, NM (United States)
  15. University of Washington, Seattle, WA (United States); University of Alberta, Edmonton, AB (Canada)
  16. Northwestern University, Evanston, IL (United States)
+ Show Author Affiliations

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.

Research Organization:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
Sponsoring Organization:
USDOE; National Science Foundation (NSF); National Aeronautics and Space Administration (NASA)
Grant/Contract Number:
AC02-05CH11231; AST- 1715121; AST-1715763; GO8-19089X; GO9-20086X; NAS8-03060; AST-1440341; AST-1238877; AST-0909182; AST-1313422
OSTI ID:
1983280
Journal Information:
The Astrophysical Journal, Vol. 933, Issue 2; ISSN 0004-637X
Publisher:
IOP PublishingCopyright Statement
Country of Publication:
United States
Language:
English

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79 ASTRONOMY AND ASTROPHYSICS
Astronomy &amp; Astrophysics
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Quasars
Active galactic nuclei
Variable radiation sources
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