Volume 649, May 2021
First science highlights from SRG/eROSITA
|Number of page(s)||9|
|Section||Letters to the Editor|
|Published online||07 May 2021|
Letter to the Editor
The eROSITA Final Equatorial-Depth Survey (eFEDS)
An X-ray-bright, extremely luminous infrared galaxy at z = 1.87
Department of Astronomy, Kyoto University,
2 Academia Sinica Institute of Astronomy and Astrophysics, 11F of Astronomy-Mathematics Building, AS/NTU, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
3 Research Center for Space and Cosmic Evolution, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
4 Dipartimento di Fisica e Astronomia, Università di Bologna, via Gobetti 93/2, 40129 Bologna, Italy
5 INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, via Gobetti 93/3, 40129 Bologna, Italy
6 Max-Planck-Institut für Extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748 Garching bei München, Germany
7 Leibniz-Institut für Astrophysik, Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
8 Astronomical Institute, Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan
9 Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08540, USA
10 Faculty of Science and Engineering, Kindai University, Higashi-Osaka 577-8502, Japan
11 Department of Economics, Management and Information Science, Onomichi City University, Hisayamada 1600-2, Onomichi, Hiroshima 722-8506, Japan
Accepted: 2 April 2021
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.
Key words: galaxies: active / X-rays: galaxies / infrared: galaxies / quasars: individual: WISE J090924.01+000211.1
© ESO 2021
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