Discovery of a hyperluminous quasar at z = 1.62 with Eddington ratio >3 in the eFEDS field confirmed by KOOLS-IFU on Seimei Telescope.

The article reports the discovery and characterization of eFEDS J082826.9-013911, a hyperluminous infrared galaxy (HyLIRG) hosting a type 1 quasar at a spectroscopic redshift of 1.622. Using optical spectroscopy with the Kyoto Okayama Optical Low-dispersion Spectrograph with optical fiber integral field unit (KOOLS-IFU) on the Seimei Telescope and submillimeter observations with SCUBA-2 on the James Clerk Maxwell Telescope, the study estimates a supermassive black hole mass of approximately 6.2 × 10^8 solar masses and an infrared luminosity of about 6.8 × 10^13 solar luminosities. The quasar exhibits a super-Eddington accretion ratio (λ_Edd ≈ 3.6), indicating one of the highest black hole accretion rates observed at cosmic noon, alongside a high star formation rate (~1300 solar masses per year). These findings suggest that eFEDS J0828-0139 is in an active growth phase of both its supermassive black hole and host galaxy, providing valuable insight into galaxy–black hole co-evolution during a critical epoch.