A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). III. Discovery of a z = 4.72 Radio Galaxy with the Lyman Break Technique

Journal Article · Sat Aug 01 04:00:00 EDT 2020 · The Astronomical Journal (Online)

DOI:https://doi.org/10.3847/1538-3881/AB98FE· OSTI ID:23013292

Yamashita, Takuji; Ikeda, Hiroyuki; Tanaka, Masayuki; Harikane, Yuichi; Kawamuro, Taiki; Uchiyama, Hisakazu ^[1]; Nagao, Tohru; Toba, Yoshiki; Kajisawa, Masaru; Matsuoka, Yoshiki ^[2]; Ono, Yoshiaki ^[3]; Akiyama, Masayuki; Ichikawa, Kohei ^[4]; Kawaguchi, Toshihiro ^[5]; Kohno, Kotaro; Lee, Kianhong ^[6]; Lee, Chien-Hsiu ^[7]; Niida, Mana ^[8]; Ogura, Kazuyuki ^[9]; Onoue, Masafusa ^[10]

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1. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
2. Research Center for Space and Cosmic Evolution, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577 (Japan)
3. Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582 (Japan)
4. Astronomical Institute, Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan)
5. Department of Economics, Management and Information Science, Onomichi City University, Onomichi, Hiroshima 722-8506 (Japan)
6. Institute of Astronomy, School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)
7. NSF’s National Optical-Infrared Astronomy Research Laboratory, 950 N. Cherry Ave., Tucson, AZ 85719 (United States)
8. Graduate School of Science and Engineering, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577 (Japan)
9. Faculty of Education, Bunkyo University, 3337, Minami-ogishima, Koshigaya, Saitama 343-8511 (Japan)
10. Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)

We report a discovery of a z = 4.72 radio galaxy, HSC J083913.17+011308.1, using the Lyman break technique with the Hyper Suprime-Cam Subaru Strategic Survey (HSC-SSP) catalog for Very Large Array Faint Images of the Radio Sky at Twenty centimeter radio sources. The number of known high-z radio galaxies (HzRGs) at z > 3 is quite small to constrain the evolution of HzRGs so far. The deep and wide-area optical survey by HSC-SSP enables us to apply the Lyman break technique to a large search for HzRGs. For an HzRG candidate among pre-selected r-band dropouts with a radio detection, a follow-up optical spectroscopy with the Gemini Multi-Object Spectrographs (GMOS)/Gemini has been performed. The obtained spectrum presents a clear Lyα emission line redshifted to z = 4.72. The spectral energy distribution fitting analysis with the rest-frame UV and optical photometries suggests the massive nature of this HzRG with logM{sub ∗}/M{sub ⊙}=11.4. The small equivalent width of Lyα and the moderately red UV colors indicate its dusty host galaxy, implying a chemically evolved and dusty system. The radio spectral index does not meet a criterion for an ultra-steep spectrum, α{sub 1400}{sup 325} of −1.1 and α{sub 1400}{sup 150} of −0.9, demonstrating that the HSC-SSP survey compensates for a subpopulation of HzRGs that are missed in surveys focusing on an ultra-steep spectral index.

• OSTI ID: 23013292
• Journal Information: The Astronomical Journal (Online), Journal Name: The Astronomical Journal (Online) Journal Issue: 2 Vol. 160; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CATALOGS
DETECTION
EMISSION
ENERGY SPECTRA
LYMAN LINES
PHOTOMETRY
RADIO GALAXIES
RED SHIFT
SPECTROSCOPY