The eROSITA Final Equatorial-Depth Survey (eFEDS): An X-ray-bright, extremely luminous infrared galaxy at z = 1.87

Yoshiki Toba, Marcella Brusa, Teng Liu, Johannes Buchner, Yuichi Terashima, Tanya Urrutia, Mara Salvato, Masayuki Akiyama, Riccardo Arcodia, Andy D. Goulding, Yuichi Higuchi, Kaiki T. Inoue, Toshihiro Kawaguchi, Georg Lamer, Andrea Merloni, Tohru Nagao, Yoshihiro Ueda, Kirpal Nandra

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9 Scopus citations


In this study, we investigate the X-ray properties of WISE J090924.01+000211.1 (WISEJ0909+0002), an extremely luminous infrared (IR) galaxy (ELIRG) at zspec = 1.871 in the eROSITA Final Equatorial-Depth Survey. WISEJ0909+0002 is a WISE 22 μm source, located in the GAMA-09 field, which was detected by eROSITA during the performance and verification phase. The corresponding optical spectrum indicates that this object is a type-1 active galactic nucleus (AGN). Observations from eROSITA combined with Chandra and XMM-Newton archival data indicate a very luminous (L (2-10 keV) = (2.1 ± 0.2) × 1045 erg s-1) unobscured AGN with a power-law photon index of Γ=1.73-0.15+0.16 and an absorption hydrogen column density of log (NH/cm-2) < 21.0. The IR luminosity was estimated to be LIR = (1.79 ± 0.09) × 1014 L⊙ from spectral energy distribution modeling based on 22 photometric data points (X-ray to far-IR) with X-CIGALE, which confirmed that WISEJ0909+0002 is an ELIRG. A remarkably high LIR despite very low NH would indicate that we are witnessing a short-lived phase in which hydrogen gas along the line of sight is blown outward, whereas warm and hot dust heated by AGNs still exists. As a consequence of the eROSITA All-Sky Survey, 6.8-5.6+16 × 102 such X-ray-bright ELIRGs are expected to be discovered in the entire extragalactic sky (|b| > 10°). This can potentially be the key population to constrain the bright end of IR luminosity functions.

Original languageEnglish (US)
Article numberL11
JournalAstronomy and Astrophysics
StatePublished - May 1 2021

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Galaxies: active
  • Infrared: galaxies
  • Quasars: individual: WISE J090924.01+000211.1
  • X-rays: galaxies


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