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

TL;DR

This paper reports the discovery of a hyperluminous quasar at redshift 1.62 with a super-Eddington accretion rate, confirmed through optical and submillimeter observations, indicating an extremely active black hole in the early universe.

Contribution

It presents the first detailed multi-wavelength analysis of a hyperluminous quasar with super-Eddington accretion at cosmic noon, combining optical spectroscopy and infrared data.

Findings

Black hole mass estimated at 6.2 x 10^8 solar masses.

Infrared luminosity confirms a HyLIRG with 6.8 x 10^13 L_sun.

Eddington ratio exceeds 3, indicating super-Eddington accretion.

Abstract

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