February 2-5, 2021

Oral Presentation

eROSITA view of an extremely luminous infrared galaxy at z = 1.87

Author(s): Yoshiki Toba (Kyoto Univ./ASIAA), Marcella Brusa (Univ. of Bologna/INAF), Teng Liu (MPE), Johannes Buchner (MPE), Yuichi Terashima (Ehime Univ.), Tanya Urrutia (AIP), Mara Salvato (MPE), and eROSITA-HSC AGN collaboration

Presenter: Yoshiki Toba (Kyoto University / ASIAA)

We report the X-ray properties of an extremely luminous infrared (IR) galaxy (ELIRG) at z_spec= 1.871, WISE J090924.01+000211.1 (WISEJ0909+0002) in the eROSITA Final Equatorial Depth Survey (eFEDS). WISEJ0909+0002 is discovered from a 22 µm-selected sample with eROSITA detection in the GAMA 9th field. Its optical spectrum indicates that this object is a type 1 Active Galactic Nucleus (AGN). The eROSITA and archival Chandra and XMM-Newton observations indicate a very luminous (L (2-10 keV) = (2.1 ± 0.2) × 10^45 erg/s) unobscured AGN with a power-law photon index of Gamma = 1.7 ± 0.1 and an absorption hydrogen column density of log NH = 20.1^+0.8_-0.7 cm^-2. Spectral Energy Distribution modeling based on 22 photometric data (X-ray to far-IR) with X-CIGALE estimates the IR luminosity to LIR = (1.82 ± 0.09) × 10^14 Lsun, confirming WISEJ0909+0002 as an ELIRG. We find that the relation between the ratio of hard X-ray and AGN 6 µm luminosities, and Eddington ratio, follows an empirical relation for AGNs reported by Toba et al. (2019a). As a consequence of eROSITA all-sky survey, 68 such X-ray bright ELIRGs are expected to be discovered in the entire extragalactic sky (|b| ≥10 deg), which will be the key population to constrain the bright-end of X-ray and/or IR luminosity functions (Toba et al. 2021b, Astronomy and Astrophysics Letters, submitted).

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