A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). IV. Rapidly Growing (Super)Massive Black Holes in Extremely Radio-loud Galaxies

Creators: Ichikawa, Kohei; Yamashita, Takuji; Toba, Yoshiki; Nagao, Tohru; Inayoshi, Kohei; Charisi, Maria; He, Wanqiu; Wagner, Alexander Y.; Akiyama, Masayuki; Vijarnwannaluk, Bovornpratch; Chen, Xiaoyang; Kajisawa, Masaru; Kawamuro, Taiki; Lee, Chien-Hsiu; Matsuoka, Yoshiki; Schramm, Malte; Suh, Hyewon; Tanaka, Masayuki; Uchiyama, Hisakazu; Ueda, Yoshihiro; Pflugradt, Janek; Fukuchi, Hikaru

Abstract

We present the optical and infrared properties of 39 extremely radio-loud galaxies discovered by cross-matching the Subaru/Hyper Suprime-Cam (HSC) deep optical imaging survey and VLA/FIRST 1.4 GHz radio survey. The recent Subaru/HSC strategic survey revealed optically faint radio galaxies (RG) down to g_(AB) ∼ 26, opening a new parameter space of extremely radio-loud galaxies (ERGs) with radio-loudness parameter of log R_(rest) = log(f_(1.4GHz,rest)/f_(g,rest)) > 4. Because of their optical faintness and small number density of ∼1 deg⁻², such ERGs were difficult to find in the previous wide but shallow or deep but small area optical surveys. ERGs show intriguing properties that are different from the conventional RGs: (1) most ERGs reside above or on the star-forming main-sequence and some of them might be low-mass galaxies with log(M⋆/M⊙) < 10. (2) ERGs exhibit a high specific black hole accretion rate, reaching the order of the Eddington limit. The intrinsic radio loudness (R_(int)), defined by the ratio of jet power over bolometric radiation luminosity, is one order of magnitude higher than that of radio quasars. This suggests that ERGs harbor a unique type of active galactic nuclei (AGN) that show both powerful radiations and jets. Therefore, ERGs are prominent candidates of very rapidly growing black holes reaching Eddington-limited accretion just before the onset of intensive AGN feedback.

Additional Information

© 2021. The American Astronomical Society. Received 2020 May 3; revised 2021 July 19; accepted 2021 August 4; published 2021 October 29. We thank the anonymous referee for helpful suggestions that strengthened the paper. We thank Yoshiyuki Inoue for providing us the blazar sequence SED templates. This work is supported by Program for Establishing a Consortium for the Development of Human Resources in Science and Technology, Japan Science and Technology Agency (JST) and is partially supported by Japan Society for the Promotion of Science (JSPS) KAKENHI (18K13584 and 20H01939; K. Ichikawa, 18J01050 and 19K14759; Y. Toba, 16H03958, 17H01114, 19H00697; T. Nagao, 17J09016: T. Kawamuro, 19K03862: A.Y. Wagner). M. Charisi acknowledges support from the National Science Foundation (NSF) NANOGrav Physics Frontier Center, award number 1430284. The Hyper Suprime-Cam (HSC) collaboration includes the astronomical communities of Japan and Taiwan, and Princeton University. The HSC instrumentation and software were developed by the National Astronomical Observatory of Japan (NAOJ), the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), the University of Tokyo, the High-Energy Accelerator Research Organization (KEK), the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan (ASIAA), and Princeton University. Funding was contributed by the FIRST program from the Japanese Cabinet Office, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the Japan Society for the Promotion of Science (JSPS), Japan Science and Technology Agency (JST), the Toray Science Foundation, NAOJ, Kavli IPMU, KEK, ASIAA, and Princeton University. This paper makes use of software developed for the Large Synoptic Survey Telescope. We thank the LSST Project for making their code available as free software at http://dm.lsst.org. This paper is based on data collected at the Subaru Telescope and retrieved from the HSC data archive system, which is operated by the Subaru Telescope and Astronomy Data Center (ADC) at NAOJ. Data analysis was in part carried out with the cooperation of the Center for Computational Astrophysics (CfCA), NAOJ. The Pan-STARRS1 Surveys (PS1) and the PS1 public science archive have been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg, and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, the Queens University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation grant No. AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon and Betty Moore Foundation. Facilities: VLA - Very Large Array, Herschel - , WISE - , Subaru/HSC. - Software: astropy (Astropy Collaboration et al. 2013), Matplotlib (Hunter 2007), Pandas (McKinney 2010).

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