Spatially resolved K-band spectroscopy of lensed AGN ULAS J0816+2134 at z~7.45

Abstract We aim to observe the spatial structure and the MgII2799 broad emission line of the gravitationally lensed active galactic nucleus (AGN) candidate ULAS J081621.49+213442.65 at z=7.453. We report the analysis of the Gemini Near-Infrared Integral Field Spectrograph (NIFS) K-band datacubes acquired in January-February 2024. The observations showed the four lensed components of ULAS J081621.49+213442.65 separated by ~2.2", a foreground lensing galaxy, and a galaxy companion. The MgII2799 emission line was detected in the spectra of the four lensed components at the same redshift and with a similar shape. By modeling the lens configuration, we estimated a significant total flux magnification of ~9.6 mag and an intrinsic UV absolute magnitude of M3000 ~ -16.72 mag for the source. The magnification-corrected bolometric luminosity and virial black hole mass of ULAS J081621.49+213442.65, (0.35-1.17)×1044 erg/s and (6.33+/-1.56)×104Msun, fall within the intermediate black hole-mass regime and indicate a super-Eddington growth rate of Lbol/LEdd>4.