A dual AGN at z = 5.4 associated with a Lyman-alpha Nebula in the Center of a Cosmic Filament

TL;DR

This paper reports the discovery of a rare dual AGN system at redshift 5.4, associated with an extended Lyα nebula, providing new insights into high-redshift galaxy evolution and AGN feedback mechanisms.

Contribution

It presents one of the highest redshift spectroscopically confirmed dual AGNs, identified through JWST observations, with detailed analysis of its environment and extended Lyα emission.

Findings

Discovery of a dual AGN at z=5.4 with 10.4 pkpc separation.

Detection of an extended Lyα nebula >22 kpc at high redshift.

Higher-than-expected fraction of dual AGNs at high redshift.

Abstract

Predictions from current theories and simulations suggest that dual AGN systems are exceedingly rare at high redshifts. The intense radiation and powerful outflows from AGNs regulate star formation, heat the interstellar medium, and drive massive gas outflows that shape the host galaxy and its surroundings. One manifestation of AGN feedback is the creation of extended Ly$\alpha$ nebulae. However, identifying these systems at high-$z$ is challenging. Here, we report a remarkable dual AGN candidate at $z \sim 5.4$ using JWST NIRCam and NIRSpec, with a separation of $\sim1.7$ arcseconds ($\sim10.4$ pkpc). This is one of the highest spectroscopically confirmed redshift dual AGNs discovered. Photometric SED fitting shows excellent agreement with AGN templates, strongly suggesting a rare dual AGN system. BPT diagrams and high ionisation lines further support the presence of AGNs. VLT/MUSE observations reveal strong extended Ly$\alpha$ emission, extending to $>22$ kpc, making it one of the most extended Ly$\alpha$ nebulae at $z \sim 6$. This provides observational evidence of anisotropic AGN-driven photoionization or shocks. The high Ly$\alpha$ escape fraction also indicates an AGN outflow. This dual AGN candidate is also associated with a well-defined overdensity, potentially at the center of a $z \sim 5.4$ protocluster or filamentary structure node. Further analysis indicates the fraction of dual AGNs is significantly higher than theoretically expected at high redshifts. This discovery provides a new opportunity to study dual AGN interactions and their impact on the circumgalactic medium and cosmic structure evolution.