AuthorPfeifle, Ryan W.
Sexton, Remington O.
Ellison, Sara L.
Secrest, Nathan J.
Harvey, Jenna B.
AffiliationUniv Arizona, LBT Observ
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationRyan W. Pfeifle et al 2019 ApJ 883 167
RightsCopyright © 2019. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at firstname.lastname@example.org.
AbstractThe coevolution of galaxies and the supermassive black holes (SMBHs) at their centers via hierarchical galaxy mergers is a key prediction of Lambda CDM cosmology. As gas and dust are funneled to the SMBHs during the merger, the SMBHs light up as active galactic nuclei (AGNs). In some cases, a merger of two galaxies can encounter a third galaxy, leading to a triple merger, which would manifest as a triple AGN if all three SMBHs are simultaneously accreting. Using high spatial resolution X-ray, near-IR, and optical spectroscopic diagnostics, we report here a compelling case of an AGN triplet with mutual separations <10 kpc in the advanced merger SDSS J084905.51+111447.2 at z = 0.077. The system exhibits three nuclear X-ray sources, optical spectroscopic line ratios consistent with AGN in each nucleus, a high excitation near-IR coronal line in one nucleus, and broad Pa alpha detections in two nuclei. Hard X-ray spectral fitting reveals a high column density along the line of sight, consistent with the picture of late-stage mergers hosting heavily absorbed AGNs. Our multiwavelength diagnostics support a triple AGN scenario, and we rule out alternative explanations such as star formation activity, shock-driven emission, and emission from fewer than three AGN. The dynamics of gravitationally bound triple SMBH systems can dramatically reduce binary SMBH inspiral timescales, providing a possible means to surmount the "Final Parsec Problem." AGN triplets in advanced mergers are the only observational forerunner to bound triple SMBH systems and thus offer a glimpse of the accretion activity and environments of the AGNs prior to the gravitationally bound triple phase.
VersionFinal published version
SponsorsNational Aeronautics & Space Administration (NASA) [GO6-17096X, GO7-18099X]; Chandra Help Desk; National Science Foundation (NSF) [AST 1817233, AST-1715413]; CONICYT+PAI Convocatoria Nacional subvencion a instalacion en la academia convocatoria ano 2017 [PAI77170080]; National Aeronautics & Space Administration (NASA); Alfred P. Sloan Foundation; National Science Foundation (NSF); U.S. Department of Energy Office of Science United States Department of Energy (DOE); University of Arizona; Brazilian Participation Group; Brookhaven National Laboratory United States Department of Energy (DOE); Carnegie Mellon University; University of Florida; French Participation Group; German Participation Group; Harvard University; Instituto de Astrofisica de Canarias; Michigan State/Notre Dame/JINA Participation Group; Johns Hopkins University; Lawrence Berkeley National Laboratory United States Department of Energy (DOE); Max Planck Institute for Astrophysics; Max Planck Institute for Extraterrestrial Physics; New Mexico State University; New York University; Ohio State University; Pennsylvania State University; University of Portsmouth; Princeton University; Spanish Participation Group; University of Tokyo; University of Utah; Vanderbilt University; University of Virginia; University of Washington; Yale University
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