Two Peas in a Pod: The First Confirmed Dual Active Galactic Nucleus within a Green Pea Galaxy System

Konstantinos Kouroumpatzakis, Peter G. Boorman, Jiří Svoboda, Ryan Pfeifle, Abhijeet Borkar, Maitrayee Gupta, Daniel Stern, Andreas Zezas

First listed 2026-07-21 | Last updated 2026-07-20

Abstract

The growth of galaxies in the early Universe is thought to be dominated by compact, intensely star-forming systems, yet the corresponding growth of supermassive black holes (SMBHs) within such environments remains poorly constrained. Green Pea galaxies are nearby analogs of rapidly assembling galaxies in the early Universe owing to their compact morphologies, intense star formation, low metallicities, and extreme ionization conditions. Although galaxy interactions are thought to trigger episodes of rapid SMBH growth, direct observations of simultaneous accretion onto multiple SMBHs in compact, intensely star-forming galaxies are lacking. Here we report the discovery of the first confirmed dual active galactic nucleus (AGN) in a Green Pea system, SDSS J162209.41+352107.5. Chandra imaging resolves two luminous hard X-ray sources separated by 8.4 kpc in projection, demonstrating simultaneous accretion onto two SMBHs. Follow-up Keck spectroscopy confirms that the two optical nuclei share a common redshift and independently exhibit broad Balmer emission and high-ionization AGN emission lines. Unlike most known dual AGN, which are typically found in massive mergers, J162209.41+352107.5 is a compact low-mass system analogous to galaxies thought to dominate early phases of galaxy assembly. These findings demonstrate that efficient growth of multiple SMBHs can occur in such environments and establish Green Pea galaxies as nearby laboratories for investigating the interplay between galaxy interactions, star formation, and black-hole growth under conditions analogous to those prevalent in the young Universe.

Short digest

Kouroumpatzakis et al. identify SDSS J162209.41+352107.5 (J1622+3521) as the first confirmed dual AGN in a Green Pea system, using Chandra to resolve two hard X-ray nuclei separated by 8.4 kpc. Keck/DEIMOS spectroscopy shows that the two components share a common redshift and each independently displays broad Balmer emission, high-ionization lines including He II, [Ne V], and [Fe VII], and AGN-like narrow-line ratios. The system extends confirmed dual-AGN hosts into the compact, low-mass, intensely star-forming and low-metallicity regime, making it a nearby analogue for merger-assisted black-hole growth in rapidly assembling early galaxies. Its main significance is direct evidence that an interaction can fuel simultaneous, efficient accretion onto two SMBHs outside the massive-merger population that dominates known dual AGN.

Key figures to inspect

• Figure 1. The essential discovery image: DECaLS reveals the disturbed two-nucleus morphology and tidal structure, while Chandra spatially resolves the two X-ray sources and directly measures their 8.4 kpc projected separation.
• Figure 2. Shows the decisive spatially separated Keck/DEIMOS spectra for both X-ray nuclei, establishing their common redshift and providing the optical basis for treating the pair as a physically associated dual AGN.
• Figure 5. The narrow-line BPT placement demonstrates that both decomposed nuclei lie in the AGN regime, helping rule out star formation as the origin of the optical excitation in this extreme compact system.
• Figure 7. Connects the extinction-corrected broad Hα and intrinsic hard X-ray luminosities of both components to an empirical AGN relation, providing a compact multiwavelength consistency check on the two accreting SMBHs.
• Figure 8. Places both virial black-hole mass estimates in the black-hole-mass--stellar-mass plane alongside local AGN, broad-line Green Peas, and scaling relations, highlighting the unusual low-mass host regime reached by this dual system.