eROSITA Final Equatorial-Depth Survey (eFEDS)

eFEDS X-ray view of WERGS radio galaxies selected by the Subaru/HSC and VLA/FIRST survey

¹ Max Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching bei München, Germany
² Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578, Japan
³ Astronomical Institute, Tohoku University, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan
e-mail: k.ichikawa@astr.tohoku.ac.jp
⁴ National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
⁵ Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
⁶ ALMA Project, National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan
⁷ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, PR China
⁸ Department of Economics, Management and Information Science, Onomichi City University, Hisayamada 1600-2, Onomichi, Hiroshima 722-8506, Japan
⁹ Nućleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejéercito Libertador 441, Santiago, Chile
¹⁰ Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA
¹¹ Research Center for Space and Cosmic Evolution, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
¹² Graduate school of Science and Engineering, Saitama Univ. 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan
¹³ Gemini Observatory/NSF’s NOIRLab, 670 N. A’ohoku Place, Hilo, HI 96720, USA
¹⁴ Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
¹⁵ Academia Sinica Institute of Astronomy and Astrophysics, 11F of Astronomy-Mathematics Building, AS/NTU, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan

Received: 15 June 2022
Accepted: 13 February 2023

Abstract

We constructed the eROSITA X-ray catalog of radio galaxies discovered by the WERGS survey, made by cross-matching the wide area Subaru/Hyper Suprime-Cam (HSC) optical survey and VLA/FIRST 1.4 GHz radio survey. We report finding 393 eROSITA detected radio galaxies in the 0.5−2 keV band in the eFEDS field covering 140 deg². Thanks to the wide and medium depth eFEDS X-ray survey down to f_{0.5 − 2 keV} = 6.5 × 10⁻¹⁵ erg s⁻¹ cm⁻², the sample contains the rare and most X-ray luminous radio galaxies above the knee of the X-ray luminosity function, spanning 44 < log(L_{0.5−2 keV}^(abs,corr)/erg s⁻¹) < 46.5 at 1 < z < 4. The sample also contains the sources around and below the knee for the sources 41 < log(L_{0.5−2 keV}^(abs,corr)/erg s⁻¹) < 45 at z < 1. Based on the X-ray properties obtained by the spectral fitting, 37 sources show obscured active galactic nucleus (AGN) signatures with log(N_H/cm⁻²) > 22. These obscured and radio AGN reside in 0.4 < z < 3.2, indicating that they are obscured counterparts of the radio-loud quasar, which were missed in the previous optical quasar surveys. By combining radio and X-ray luminosities, we also investigated the jet production efficiency η_jet = η_radP_jet/L_AGN,bol by utilizing the jet power of P_jet. We find that there are 14 sources with extremely high jet production efficiency at η_jet ≈ 1. This high η_jet value might be a result of the decreased radiation efficiency of η_rad < 0.1, due to the low accretion rate for those sources, and/or of the boosting due to the decline of L_AGN,bol by a factor of 10−100 by keeping P_jet constant in the previous Myr, indicating the experience of the AGN feedback. Finally, inferring the BH masses from the stellar mass, we find that X-ray luminous sources show the excess of the radio emission with respect to the value estimated from the fundamental plane. This radio emission excess cannot be explained by the Doppler boosting alone, and therefore the disk–jet connection of X-ray luminous eFEDS-WERGS is fundamentally different from the conventional fundamental plane which mainly covers the low-accretion regime.