eROSITA Final Equatorial-Depth Survey (eFEDS)

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 f0.5 − 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(L0.5−2 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(L0.5−2 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(NH/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 ηjet = ηradPjet/LAGN,bol by utilizing the jet power of Pjet. We find that there are 14 sources with extremely high jet production efficiency at ηjet ≈ 1. This high ηjet value might be a result of the decreased radiation efficiency of ηrad < 0.1, due to the low accretion rate for those sources, and/or of the boosting due to the decline of LAGN,bol by a factor of 10−100 by keeping Pjet 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.