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

Abstract

We report the discovery of a hyperluminous type 1 quasar (eFEDS J082826.9-013911; eFEDSJ0828-0139) at $z_{\mathrm{spec}}$ = 1.622 with a super-Eddington ratio (${\lambda }_{\mathrm{Edd}}$). We perform the optical spectroscopic observations with KOOLS-IFU on the Seimei Telescope. The black hole mass ($M_{\mathrm{BH}}$) based on the single-epoch method with MgII $\lambda$2798 is estimated to be $M_{\mathrm{BH}}=(6.2\pm 1.2)\times 10^8$ $M_{\odot }$. To measure the precise infrared luminosity ($L_{\mathrm{IR}}$), we obtain submillimeter data taken by SCUBA-2 on JCMT and conduct the spectral energy distribution analysis with X-ray to submillimeter data. We find that $L_{\mathrm{IR}}$ of eFEDSJ0828-0139 is $L_{\mathrm{IR}}=(6.8\pm 1.8)\times 10^{13}$ $L_{\odot }$, confirming the existence of a hypeluminous infrared galaxy (HyLIRG). ${\lambda }_{\mathrm{Edd}}$ is estimated to be ${\lambda }_{\mathrm{Edd}}=3.6\pm 0.7$, making it one of the quasars with the highest BH mass accretion rate at cosmic noon.

9 pages, 3 figures, and 3 tables, accepted for publication in PASJ