Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). III. Discovery of a z = 4.72 Radio Galaxy with Lyman Break Technique
| Autor: | Yamashita, Takuji, Nagao, Tohru, Ikeda, Hiroyuki, Toba, Yoshiki, Kajisawa, Masaru, Ono, Yoshiaki, Tanaka, Masayuki, Akiyama, Masayuki, Harikane, Yuichi, Ichikawa, Kohei, Kawaguchi, Toshihiro, Kawamuro, Taiki, Kohno, Kotaro, Lee, Chien-Hsiu, Lee, Kianhong, Matsuoka, Yoshiki, Niida, Mana, Ogura, Kazuyuki, Onoue, Masafusa, Uchiyama, Hisakazu |
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| Rok vydání: | 2020 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.3847/1538-3881/ab98fe |
| Popis: | We report a discovery of $z = 4.72$ radio galaxy, HSC J083913.17+011308.1, by using the Lyman break technique with the Hyper Suprime-Cam Subaru Strategic Survey (HSC-SSP) catalog for VLA FIRST 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 GMOS/Gemini has been performed. The obtained spectrum presents a clear Ly$\alpha$ emission line redshifted to $z=4.72$. The SED fitting analysis with the rest-frame UV and optical photometries suggests the massive nature of this HzRG with $\log{M_*/M_{\odot}} = 11.4$. The small equivalent width of Ly$\alpha$ 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: $\alpha^{325}_{1400}$ of $-1.1$ and $\alpha^{150}_{1400}$ of $-0.9$, demonstrating that the HSC-SSP survey compensates for a sub-population of HzRGs which are missed in surveys focusing on an ultra-steep spectral index. Comment: 10 pages, 5 figures, accepted for publication in AJ |
| Databáze: | arXiv |
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