A Triple AGN in a Mid-Infrared Selected Late Stage Galaxy Merger

Abstract

The co-evolution 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.

arXiv comment15 pages, 8 figures. Submitted to ApJL 24 May 2019. Accepted for publication in ApJ

References in corpus (67)

• emcee: The MCMC Hammer
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• Starburst99: Synthesis Models for Galaxies with Active Star Formation
• The Host Galaxies of AGN
• Theoretical Modeling of Starburst Galaxies
• The Host Galaxies and Classification of Active Galactic Nuclei
• Gasdynamics and Starbursts in Major Mergers
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies
• A Cosmology Calculator for the World Wide Web
• A Method of Correcting Near-Infrared Spectra for Telluric Absorption
• The MAPPINGS III Library of Fast Radiative Shock Models
• Mid-Infrared Selection of AGN with the Wide-Field Infrared Survey Explorer. I. Characterizing WISE-Selected AGN in COSMOS
• The Indo-U.S. Library of Coude Feed Stellar Spectra
• The International Pulsar Timing Array: First Data Release
• The Effects of Stellar Rotation. II. A Comprehensive Set of Starburst99 Models
• A Cosmological Framework for the Co-Evolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies: II. Formation of Red Ellipticals
• Low-Frequency Gravitational Waves from Massive Black Hole Binaries: Predictions for LISA and Pulsar Timing Arrays
• H I, H II, and R-Band Observations of a Galactic Merger Sequence
• An XMM-Newton spectral survey of 12 micron selected galaxies. I. X-ray data
• Low-frequency gravitational radiation from coalescing massive black hole binaries in hierarchical cosmologies
• The unusual emission line spectrum of IZw1
• Galaxy-Wide Shocks in Late-Merger Stage Luminous Infrared Galaxies
• Galaxy pairs in the Sloan Digital Sky Survey - IX: Merger-induced AGN activity as traced by the Wide-field Infrared Survey Explorer
• Understanding Dual AGN Activation in the Nearby Universe
• New Spectral Model for Constraining Torus Covering Factors from Broadband X-ray Spectra of Active Galactic Nuclei
• Star formation and AGN activity in SDSS cluster galaxies
• Growing supermassive black holes in the late stages of galaxy mergers are heavily obscured
• Galaxy Interactions Trigger Rapid Black Hole Growth: an unprecedented view from the Hyper Suprime-Cam Survey
• A definitive merger-AGN connection at z~0 with CFIS: mergers have an excess of AGN and AGN hosts are more frequently disturbed
• The Prevalence of Gas Outflows in Type 2 AGNs
• Dynamics of triple black hole systems in hierarchically merging massive galaxies
• The power of infrared AGN selection in mergers: a theoretical study
• The Local Nanohertz Gravitational-Wave Landscape From Supermassive Black Hole Binaries
• The Gravitational Wave Background from Massive Black Hole Binaries in Illustris: spectral features and time to detection with pulsar timing arrays
• Are Compton-Thick AGN the Missing Link Between Mergers and Black Hole Growth?
• Post-Newtonian Evolution of Massive Black Hole Triplets in Galactic Nuclei: IV. Implications for LISA
• Active Galactic Nucleus Pairs from the Sloan Digital Sky Survey. I. The Frequency on ~ 5-100 kpc Scales
• The most extreme ultraluminous X-ray sources: evidence for intermediate-mass black holes?
• A close-pair binary in a distant triple supermassive black-hole system
• A population of luminous accreting black holes with hidden mergers
• Kinematic Linkage Between the Broad and Narrow Line Emitting Gas in AGN
• Incidence of WISE-Selected Obscured AGNs in Major Mergers and Interactions from the SDSS
• Interactions between multiple supermassive black holes in galactic nuclei: a solution to the final parsec problem
• SALT Long-slit Spectroscopy of Luminous Obscured Quasars: An Upper Limit on the Size of the Narrow-Line Region?
• The importance of warm, AGN-driven outflows in the nuclear regions of nearby ULIRGs
• Compton thick AGN in the NuSTAR era
• Buried AGNs in Advanced Mergers:Mid-infrared color selection as a dual AGN finder
• The Chandra COSMOS Legacy Survey: Compton Thick AGN at high redshift
• Evidence for Merger-Driven Growth in Luminous, High-z, Obscured AGN in the CANDELS/COSMOS Field
• Gemini Long-slit Observations of Luminous Obscured Quasars: Further Evidence for an Upper Limit on the Size of the Narrow-Line Region
• NuSTAR Observations of Heavily Obscured Quasars at z ~ 0.5
• An Offset Seyfert 2 Nucleus in the Minor Merger System NGC 3341
• Buried Black Hole Growth in IR-selected Mergers: New Results from Chandra
• Discovery of a Probable Physical Triple Quasar
• Discovery of a dual active galactic nucleus with ~ 8 kpc separation
• An Optically Obscured AGN in a Low Mass, Irregular Dwarf Galaxy: A Multi-Wavelength Analysis of J1329+3234
• Evidence for Three Accreting Black Holes in a Galaxy at z~1.35: A Snapshot of Recently Formed Black Hole Seeds?
• NuSTAR unveils a heavily obscured low-luminosity Active Galactic Nucleus in the Luminous Infrared Galaxy NGC 6286
• Evidence from the Very Long Baseline Array that J1502SE/SW are Double Hotspots, not a Supermassive Binary Black Hole
• SDSS J1056+5516: A Triple AGN or an SMBH Recoil Candidate?
• Stronger Constraints on the Evolution of the $M_{\mathrm{BH}}-{\sigma }_{\ast }$ Relation up to $z\sim 0.6$
• Stellar Velocity Dispersion in Dissipative Galaxy Mergers with Star Formation
• The NGC 3341 minor merger: a panchromatic view of the active galactic nucleus in a dwarf companion
• Caught in the Act: Discovery of a Physical Quasar Triplet
• $r$-process nucleosynthesis in the early Universe through fast mergers of compact binaries in triple systems
• Very long baseline interferometry observation of the triple AGN candidate J0849+1114

Cited by in corpus (26)

• The Quest for Dual and Binary Supermassive Black Holes: A Multi-Messenger View
• A hard X-ray view of Luminous and Ultra-luminous Infrared Galaxies in GOALS: I - AGN obscuration along the merger sequence
• Resolving the Complex Evolution of a Supermassive Black Hole Triplet in a Cosmological Simulation
• New multiple AGN systems with sub-arcsec separation: confirmation of candidates selected via the novel GMP method
• A Trio of Massive Black Holes Caught in the Act of Merging
• A Chandra X-ray Survey of Optically Selected AGN Pairs
• AGN Triality of Triple Mergers: Detection of Faint X-ray Point Sources
• Double-peak emission line galaxies in the SDSS catalogue. A minor merger sequence
• A Triple AGN in the NGC 7733-7734 Merging Group
• Supermassive black hole fueling in IllustrisTNG: Impact of environment
• A hadronic emission model for black hole-disc impacts in the blazar OJ 287
• Dynamics of supermassive black hole triples in the ROMULUS25 cosmological simulation
• Merging timescale for supermassive black hole binary in interacting galaxy NGC 6240
• 2MASX J00423991+3017515: An offset active galactic nucleus in an interacting system
• AGN Triality of Triple Mergers: Multi-wavelength Classifications
• The Intriguing Parsec-Scale Radio Structure in the "Offset AGN" KISSR 102
• Revisiting the complex kinematics of ionized gas at the central region of NGC 1068: evidence of an additional active galactic nucleus?
• Triple and Quadruple Black Holes in the ASTRID Simulation at $z\sim 2$
• Testing the Radio-Selection Method of Dual Active Galactic Nuclei in the Stripe 82 Field
• 3D spectroscopy with GTC-MEGARA of the triple AGN candidate in SDSS J102700.40+174900.8
• The Messy Nature of Fiber Spectra: Star-Quasar Pairs Masquerading as Dual Type 1 AGNs
• Very Large Array Multi-band Radio Imaging of the Triple AGN Candidate SDSS J0849+1114
• A candidate quadruple AGN system at $z\sim 3$
• Investigating the Bulge Morphology of Dual AGN Host Galaxies from the GOTHIC survey
• Dual AGN in the Horizon-AGN simulation and their link to galaxy and massive black hole mergers, with an excursus on multiple AGN
• SDSS J153231.80+420342.7: a triple black hole candidate with a close binary black hole