Chandra X-ray Spectral Evidence of the Dual AGN Nature of the Gravitational lens MG B2016+112 at z=3.273 with 175 pc separation

Using a new 175 ks Chandra X-ray observation of the z=3.273 radio-loud gravitational lens system MG B2016+112, researchers report definitive X-ray spectral evidence that the system contains a dual active galactic nucleus (AGN). With a projected separation of 175 parsecs, this is the tightest separation confirmed AGN pair at high redshift.

Prior multi-epoch very long baseline interferometry (VLBI) and archival Chandra data had revealed two distinct emitters, but they could not rule out a single AGN with a complex, highly magnified jet. The new Chandra observations allow a separate spectral analysis of each source. The team finds strong intrinsic absorption (N_H > 4 x 10^22 cm^-2, at 3 sigma confidence) at the source redshift for the highly magnified source inside the caustic, identifying it as an obscured AGN.

Together with the previously known type II AGN outside the caustic, this confirms a compact dual AGN system in MG B2016+112. Ongoing and future surveys using facilities such as Euclid, SKA, and the Rubin and Roman observatories are expected to uncover more such systems, probing supermassive black hole evolution and gravitational wave precursors.