"Changing-look" active galactic nuclei (CL-AGNs) challenge our basic ideas about the physics of accretion flows and circumnuclear gas around supermassive black holes. Using first-year Sloan Digital Sky Survey V (SDSS-V) repeated spectroscopy of nearly 29,000 previously known active galactic nuclei (AGNs), combined with dedicated follow-up spectroscopy, and publicly available optical light curves, we have identified 116 CL-AGNs where (at least) one broad emission line has essentially (dis-)appeared, as well as 88 other extremely variable systems. Our CL-AGN sample, with 107 newly identified cases, is the largest reported to date, and includes ∼0.4% of the AGNs reobserved in first-year SDSS-V operations. Among our CL-AGNs, 67% exhibit dimming while 33% exhibit brightening. Our sample probes extreme AGN spectral variability on months to decades timescales, including some cases of recurring transitions on surprisingly short timescales (≲2 months in the rest frame). We find that CL events are preferentially found in lower-Eddington-ratio (fEdd) systems: Our CL-AGNs have a fEdd distribution that significantly differs from that of a carefully constructed, redshift- and luminosity-matched control sample (Anderson–Darling test yielding pAD ≈ 6 × 10−5; median fEdd ≈ 0.025 versus 0.043). This preference for low fEdd strengthens previous findings of higher CL-AGN incidence at lower fEdd, found in smaller samples. Finally, we show that the broad Mg ii emission line in our CL-AGN sample tends to vary significantly less than the broad Hβ emission line. Our large CL-AGN sample demonstrates the advantages and challenges in using multi-epoch spectroscopy from large surveys to study extreme AGN variability and physics.
Exploring Changing-look Active Galactic Nuclei with the Sloan Digital Sky Survey V: First Year Results
- Creators
- Zeltyn, Grisha
- Trakhtenbrot, Benny
- Eracleous, Michael
- Yang, Qian
- Green, Paul
- Anderson, Scott F.
- LaMassa, Stephanie
- Runnoe, Jessie
- Assef, Roberto J.
- Bauer, Franz E.
- Brandt, W. N.
- Davis, Megan C.
- Frederick, Sara E.
- Fries, Logan B.
- Graham, Matthew J.1
- Grogin, Norman A.
- Guolo, Muryel
- Hernández-García, Lorena
- Koekemoer, Anton M.
- Krumpe, Mirko
- Liu, Xin
- Martínez-Aldama, Mary Loli
- Ricci, Claudio
- Schneider, Donald P.
- Shen, Yue
- Śniegowska, Marzena
- Temple, Matthew J.
- Trump, Jonathan R.
- Xue, Yongquan
- Brownstein, Joel R.
- Dwelly, Tom
- Morrison, Sean
- Bizyaev, Dmitry
- Pan, Kaike
- Kollmeier, Juna A.
Abstract
Copyright and License
© 2024. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Acknowledgement
We thank the anonymous referee and statistics editor for their insightful and constructive comments, which helped us improve the paper. We thank Jamie Burke, Joseph Farah, Daichi Hiramatsu, Estefania Padilla Gonzalez, Craig Pellegrino, Megan Newsome, and Giacomo Terreran for their assistance with the acquisition and reduction of LCOGT data. We acknowledge support from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 950533; G.Z., B.T., M.Ś); the Israel Science Foundation (grant No. 1849/19; G.Z., B.T., M.Ś); FONDECYT Regular #123171 (R.J.A.), #1200495 (F.E.B.), and #1230345 (C.R.); ANID BASAL project FB210003 (R.J.A., F.E.B., C.R.); ANID Millennium Science Initiative ICN12_009 (F.E.B., L.H.G.); DLR grant FKZ 50 OR 2307 (M.K.); NSF grants AST-1715579, AST-2009947 (Y.S.), and AST-2206499 (X.L.); FONDECYT Postdoctorado #3220516 (M.J.T.); FONDECYT Iniciación #11241477 (L.H.G.); NSFC grant Nos. 12025303, 12393814, and 11890693 (Y.Q.X.); Millenium Nucleus NCN19-058 TITANs (M.L.M.-A.); NSF grant AST-2106990; and the Penn State Eberly Endowment (W.N.B).
Funding for the Sloan Digital Sky Survey V has been provided by the Alfred P. Sloan Foundation, the Heising-Simons Foundation, the National Science Foundation, and the participating institutions. SDSS acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. SDSS telescopes are located at Apache Point Observatory, funded by the Astrophysical Research Consortium and operated by New Mexico State University, and at Las Campanas Observatory, operated by the Carnegie Institution for Science. The SDSS website is www.sdss.org.
SDSS is managed by the Astrophysical Research Consortium for the participating institutions of the SDSS Collaboration, including Caltech, The Carnegie Institution for Science, Chilean National Time Allocation Committee (CNTAC) ratified researchers, The Flatiron Institute, the Gotham Participation Group, Harvard University, Heidelberg University, The Johns Hopkins University, L'Ecole polytechnique fédérale de Lausanne (EPFL), Leibniz-Institut für Astrophysik Potsdam (AIP), Max-Planck-Institut für Astronomie (MPIA Heidelberg), Max-Planck-Institut für Extraterrestrische Physik (MPE), Nanjing University, National Astronomical Observatories of China (NAOC), New Mexico State University, The Ohio State University, Pennsylvania State University, Smithsonian Astrophysical Observatory, Space Telescope Science Institute (STScI), the Stellar Astrophysics Participation Group, Universidad Nacional Autónoma de México, University of Arizona, University of Colorado Boulder, University of Illinois at Urbana-Champaign, University of Toronto, University of Utah, University of Virginia, Yale University, and Yunnan University.
The ZTF forced-photometry service was funded under the Heising-Simons Foundation grant No. 12540303 (PI: Graham). The Hobby–Eberly Telescope (HET) is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximillians-Universitaet Muenchen, and Georg-August Universitaet Goettingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly.
Facilities
Sloan (SDSS and BOSS) - , ING:Herschel (ISIS) - , LCOGT (FTN: FLOYDS) - , ARC (KOSMOS) - , HET (LRS2) - McDonald Observatory's Hobby-Eberly Telescope
Software References
AstroPy (Astropy Collaboration et al. 2013, 2018, 2022), Matplotlib (Hunter 2007), NumPy (Harris et al. 2020), SciPy (Virtanen et al. 2020), PyQSOFit (Guo et al. 2018; Shen et al. 2019), floyds_pipeline, PypeIt (Prochaska et al. 2020), Panacea
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Additional details
- ISSN
- 1538-4357
- European Research Council
- 950533
- Israel Science Foundation
- 1849/19
- Fondo Nacional de Desarrollo Científico y Tecnológico
- 123171
- Fondo Nacional de Desarrollo Científico y Tecnológico
- 1200495
- Fondo Nacional de Desarrollo Científico y Tecnológico
- 1230345
- Agencia Nacional de Investigación y Desarrollo
- FB210003
- Agencia Nacional de Investigación y Desarrollo
- ICN12_009
- Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)
- FKZ 50 OR 2307
- National Science Foundation
- AST-1715579
- National Science Foundation
- AST-2009947
- National Science Foundation
- AST-2206499
- Fondo Nacional de Desarrollo Científico y Tecnológico
- 3220516
- Fondo Nacional de Desarrollo Científico y Tecnológico
- 11241477
- National Natural Science Foundation of China
- 12025303
- National Natural Science Foundation of China
- 12393814
- National Natural Science Foundation of China
- 11890693
- Agencia Nacional de Investigación y Desarrollo
- NCN19-058
- National Science Foundation
- AST-2106990
- Pennsylvania State University
- Eberly Endowment
- Alfred P. Sloan Foundation
- Heising-Simons Foundation
- 12540303
- Caltech groups
- Zwicky Transient Facility