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Long-term decline of the mid-infrared emission of normal galaxies: dust echo of tidal disruption flare?

Wang, Tinggui and Yan, Lin and Dou, Liming and Jiang, Ning and Sheng, Zhenfeng and Yang, Chenwei (2018) Long-term decline of the mid-infrared emission of normal galaxies: dust echo of tidal disruption flare? Monthly Notices of the Royal Astronomical Society, 477 (3). pp. 2943-2965. ISSN 0035-8711. doi:10.1093/mnras/sty465.

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We report the discovery of a sample of 19 low-redshift (z < 0.22) spectroscopically non-Seyfert galaxies that show slow declining mid-infrared (MIR) light curves (LCs), similar to those of tidal disruption event (TDE) candidates with extreme coronal lines. Two sources also showed relatively fast-rising MIR LCs. They consist of a 61 per cent sample of Wide-field Infrared Survey Explorer (WISE) MIR variable non-Seyfert galaxies with Sloan Digital Sky Survey (SDSS) spectra. In a comparison sample of optically selected Seyfert galaxies, the fraction of sources with such a LC is only 15 per cent. After rejecting five plausible obscured Seyfert galaxies with red MIR colours, the remaining 14 objects are studied in detail in this article. We fit the declining part of the LC with an exponential law and the decay time is typically one year. The observed peak MIR luminosities (νLν) after subtracting host galaxies are in the range of a few 10^(42)–10^(44) erg s^(−1), with a median of 5 × 10^(43) erg s^(−1) in the W2 band. The black hole masses are distributed over a wide range, with more than half between 10^7and 10^8 M⊙, but are significantly different from those of optical/UV selected TDEs. Furthermore, MIR luminosities are correlated with the black hole mass, stellar mass or luminosity of their host bulges. Most galaxies in the sample are red and luminous, with an absolute r magnitude between −20 and −23. We estimate the rate of event as about 10^(−4) galaxy^(−1) yr^(−1) among luminous red galaxies. We discuss several possibilities for variable infrared sources and conclude that most likely they are caused by short sporadic fuelling of supermassive black holes via either the instability of accretion flows or tidal disruption of stars.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Wang, Tinggui0000-0002-1517-6792
Yan, Lin0000-0003-1710-9339
Dou, Liming0000-0002-4757-8622
Jiang, Ning0000-0002-7152-3621
Sheng, Zhenfeng0000-0001-6938-8670
Yang, Chenwei0000-0003-4975-2433
Additional Information:© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2018 February 9. Received 2018 February 2; in original form 2017 May 7. Published: 04 May 2018. We are grateful to the referee for careful reading of the manuscript and critical comments, which led to significant improvement of the presentation. We thank Dr N.C. Stone for helpful discussion. This project is supported by the National Basic Research Program of China (grant No. 2015CB857005), the NSFC through NSFC-11233002, NSFC-11421303, and U1431229 and U1731104, jointly supported by the Chinese Academy of Science and NSFC. This research makes use of data products from WISE, which is a joint project of the University of California, Los Angeles and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation and the US Department of Energy Office of Science. The SDSS-III web site is SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
National Basic Research Program of China2015CB857005
National Natural Science Foundation of ChinaNSFC-11233002
National Natural Science Foundation of ChinaNSFC-11421303
Joint Research Fund in AstronomyU1431229
Joint Research Fund in AstronomyU1731104
Chinese Academy of SciencesUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Participating InstitutionsUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Subject Keywords:accretion, accretion discs, black hole physics, supernovae: general, galaxies: active, galaxies: Seyfert, infrared: galaxies
Issue or Number:3
Record Number:CaltechAUTHORS:20180620-143513004
Persistent URL:
Official Citation:Tinggui Wang, Lin Yan, Liming Dou, Ning Jiang, Zhenfeng Sheng, Chenwei Yang; Long-term decline of the mid-infrared emission of normal galaxies: dust echo of tidal disruption flare?, Monthly Notices of the Royal Astronomical Society, Volume 477, Issue 3, 1 July 2018, Pages 2943–2965,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:87272
Deposited By: Tony Diaz
Deposited On:20 Jun 2018 21:59
Last Modified:15 Nov 2021 20:46

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