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Published February 2021 | Accepted Version + Published
Journal Article Open

Mid-infrared Outbursts in Nearby Galaxies (MIRONG). I. Sample Selection and Characterization

Abstract

Optical time-domain astronomy has grown rapidly in the past decade, but the dynamic infrared sky is rarely explored. Aiming to construct a sample of mid-infrared outbursts in nearby galaxies (MIRONG), we have conducted a systematical search of low-redshift (z < 0.35) Sloan Digital Sky Survey spectroscopic galaxies that have experienced recent mid-infrared (MIR) flares using their Wide-field Infrared Survey Explorer (WISE) light curves. A total of 137 galaxies have been selected by requiring a brightening amplitude of 0.5 mag in at least one WISE band with respect to their quiescent phases. Only a small fraction (10.9%) has corresponding optical flares. Except for the four supernovae (SNe) in our sample, the MIR luminosities of the remaining sources (L_(4.6 μm) > 10⁴² erg s⁻¹) are markedly brighter than known SNe, and their physical locations are very close to the galactic center (median <0."1). Only four galaxies are radio-loud, indicating that synchrotron radiation from relativistic jets could contribute to MIR variability. We propose that these MIR outbursts are dominated by the dust echoes of transient accretion onto supermassive black holes, such as tidal disruption events (TDEs) and turn-on (changing-look) active galactic nuclei. Moreover, the inferred peak MIR luminosity function is generally consistent with the X-ray and optical TDEs at the high end, albeit with large uncertainties. Our results suggest that a large population of transients has been overlooked by optical surveys, probably due to dust obscuration or intrinsically optical weakness. Thus, a search in the infrared band is crucial for us to obtain a panoramic picture of nuclear outburst. The multiwavelength follow-up observations of the MIRONG sample are in progress and will be presented in a series of subsequent papers.

Additional Information

© 2021. The American Astronomical Society. Received 2020 May 23; revised 2020 November 22; accepted 2020 December 7; published 2021 February 9. We are grateful to the anonymous referee for a careful reading and nice comments, which have greatly improved the paper. We thank Dr. Roc Cutri for many useful suggestions about the use of WISE and NEOWISE archival data and Dr. John Moustakas for his kind help with the usage of IDL/iSEDfit. This work is supported by the Chinese Science Foundation (NSFC-11833007, 12073025, 11421303, 11733001), Joint Research Fund in Astronomy (U1731104) under cooperative agreement between the NSFC and the CAS, Anhui Provincial Natural Science Foundation, and the Fundamental Research Funds for the Central Universities. This research makes use of data products from the Wide-field Infrared Survey Explorer, 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. This research also makes use of data products from NEOWISE-R, which is a project of the Jet Propulsion Laboratory/California Institute of Technology, funded by the Planetary Science Division of the National Aeronautics and Space Administration. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has made use of 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.

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Published - Jiang_2021_ApJS_252_32.pdf

Accepted Version - 2012.06806.pdf

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Additional details

Created:
August 22, 2023
Modified:
October 23, 2023