@article{fe951d6ef98246948cebb91893b425b1,
title = "BROAD Hβ EMISSION-LINE VARIABILITY IN A SAMPLE OF 102 LOCAL ACTIVE GALAXIES",
abstract = "A sample of 102 local (0.02 ≤ z ≤ 0.1) Seyfert galaxies with black hole masses MBH > 107M⊙ was selected from the Sloan Digital Sky Survey (SDSS) and observed using the Keck 10 m telescope to study the scaling relations between MBH and host galaxy properties. We study profile changes of the broad Hβ emission line within the three to nine year time frame between the two sets of spectra. The variability of the broad Hβ emission line is of particular interest, not only because it is used to estimate MBH, but also because its strength and width are used to classify Seyfert galaxies into different types. At least some form of broad-line variability (in either width or flux) is observed in the majority (∼66%) of the objects, resulting in a Seyfert-type change for ∼38% of the objects, likely driven by variable accretion and/or obscuration. The broad Hβ line virtually disappears in 3/102 (∼3%) extreme cases. We discuss potential causes for these changing look active galactic nuclei. While similar dramatic transitions have previously been reported in the literature, either on a case-by-case basis or in larger samples focusing on quasars at higher redshifts, our study provides statistical information on the frequency of Hβ line variability in a sample of low-redshift Seyfert galaxies.",
keywords = "accretion, accretion disks, galaxies: Seyfert, galaxies: active, galaxies: evolution, galaxies: statistics",
author = "Runco, {Jordan N.} and Maren Cosens and Bennert, {Vardha N.} and Bryan Scott and S. Komossa and Malkan, {Matthew A.} and Lazarova, {Mariana S.} and Auger, {Matthew W.} and Tommaso Treu and Daeseong Park",
note = "Funding Information: We thank the anonymous referee for valuable comments that helped to improve our paper. We thank Aaron Barth and Bernd Husemann for helpful discussions, Luis Ho for providing additional data, and William C. Keel for data reduction of the Lick spectra. J.N.R., M.C., and V.N.B. gratefully acknowledge the assistance from a National Science Foundation (NSF) Research at Undergraduate Institutions (RUI) grant AST-1312296. Note that the findings and conclusions presented in this paper do not necessarily represent the views of the NSF. V. N.B., B.S., and S.K. thank the Kavli Institute for Theoretical Physics (Santa Barbara) for their hospitality and support; the KITP is supported by NSF grant no. NSF PHY11-25915. D.P. acknowledges support through the EACOA Fellowship from The East Asian Core Observatories Association, which consists of the National Astronomical Observatories, the Chinese Academy of Science (NAOC), the National Astronomical Observatory of Japan (NAOJ), the Korean Astronomy and Space Science Institute (KASI), and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA). This research has made use of the Dirac computer cluster at the California Polytechnic State University in San Luis Obispo, maintained by Dr. Brian Granger and Dr. Ashley Ringer McDonald. Data presented in this thesis were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership between Caltech, the University of California, and NASA. The W. M. Keck Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This research has made use of the public archive of the SDSS and the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The CSS survey is funded by the National Aeronautics and Space Administration under grant no. NNG05GF22G issued through the Science Mission Directorate Near-Earth Objects Observations Program. The CRTS survey is supported by the U.S. National Science Foundation under grants AST-0909182 and AST-313422. Publisher Copyright: {\textcopyright} 2016. The American Astronomical Society. All rights reserved.",
year = "2016",
month = apr,
day = "10",
doi = "10.3847/0004-637X/821/1/33",
language = "English (US)",
volume = "821",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1",
}