The First Triple Radio Active Galactic Nucleus in an Ongoing Galaxy Merger
Creators
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1.
United States Naval Research Laboratory
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2.
Goddard Space Flight Center
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3.
Oak Ridge Associated Universities
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4.
United States Naval Observatory
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5.
George Mason University
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6.
Southeastern Universities Research Association
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7.
California Institute of Technology
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8.
Jet Propulsion Lab
Abstract
Galaxy mergers are predicted to be a critical stage of merger-driven SMBH growth and galaxy evolution. Systems exhibiting multiple active galactic nuclei (AGN) are an important observational tool for constraining the prevalence and properties of merging SMBHs. Most multi-AGN selection methods focus on the identification of AGN pairs, while few focus on the more elusive triple AGN, which are a prediction of hierarchical growth and natural laboratories for studying SMBH dynamics. These systems are rare; only two confirmed cases exist locally (z < 0.1). Here, we present a new, confirmed triple AGN system, WISEJ121857.42+103551.2/WISEJ121901.77+103515.0, with nuclear separations of 22.6 and 97 kpc, identified within a sample of spatially resolved mid-IR dual AGN. The system exhibits multiwavelength evidence for three distinct AGN hosted in an ongoing galaxy merger. To confirm the nature of this system, we present new radio observations with the Karl G. Jansky Very Large Array in A-configuration at 3, 10, and 15 GHz, providing subarcsecond resolutions, and the Very Long Baseline Array at 4.9 GHz, providing milliarcsecond resolutions. These observations confirm this system as a triple AGN, and the first triple AGN in which all three nuclei host radio AGN.
Copyright and License
© 2025. 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 for the helpful suggestions that have improved the Letter. R.W.P. gratefully acknowledges support through an appointment to the NASA Postdoctoral Program at Goddard Space Flight Center, administered by ORAU through a contract with NASA. The work of D.S. was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). This research made use of Astropy, a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2018), TOPCAT (M. B. Taylor 2005), the Common Astronomy Software Application (CASA Team et al. 2022), and the Python Blob Detector and Source Finder (N. Mohan & D. Rafferty 2015). Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the US Department of Energy Office of Science, and the Participating Institutions. The National Radio Astronomy Observatory and Green Bank Observatory are facilities of the US National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work made use of the Swinburne University of Technology software correlator, developed as part of the Australian Major National Research Facilities Programme and operated under license. Basic research in radio astronomy at the US Naval Research Laboratory is supported by 6.1 Base Funding.
Facilities
VLA - Very Large Array (NRAO), Sloan - Sloan Digital Sky Survey Telescope, VLBA - Very Long Baseline Array (NRAO).
Software References
Astropy (Astropy Collaboration et al. 2018), CASA (CASA Team et al. 2022), PyBDSF (N. Mohan & D. Rafferty 2015), TOPCAT (M. B. Taylor 2005).
Files
Schwartzman_2025_ApJL_995_L58.pdf
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Additional details
Funding
- National Aeronautics and Space Administration
- NASA Postdoctoral Program -
- National Aeronautics and Space Administration
- 80NM0018D0004
- United States Naval Research Laboratory
- 6.1 Base Funding
Dates
- Submitted
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2025-10-07
- Accepted
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2025-11-15
- Available
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2025-12-15Published