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SILVERRUSH. VIII. Spectroscopic identifications of early large-scale structures with protoclusters over 200 Mpc at z ∼ 6–7 : strong associations of dusty star-forming galaxies.

Harikane, Yuichi and Ouchi, Masami and Ono, Yoshiaki and Fujimoto, Seiji and Donevski, Darko and Shibuya, Takatoshi and Faisst, Andreas L. and Goto, Tomotsugu and Hatsukade, Bunyo and Kashikawa, Nobunari and Kohno, Kotaro and Hashimoto, Takuya and Higuchi, Ryo and Inoue, Akio K. and Lin, Yen-Ting and Martin, Crystal L. and Overzier, Roderik and Smail, Ian and Toshikawa, Jun and Umehata, Hideki and Ao, Yiping and Chapman, Scott and Clements, David L. and Im, Myungshin and Jing, Yipeng and Kawaguchi, Toshihiro and Lee, Chien-Hsiu and Lee, Minju M. and Lin, Lihwai and Matsuoka, Yoshiki and Marinello, Murilo and Nagao, Tohru and Onodera, Masato and Toft, Sune and Wang, Wei-Hao (2019) 'SILVERRUSH. VIII. Spectroscopic identifications of early large-scale structures with protoclusters over 200 Mpc at z ∼ 6–7 : strong associations of dusty star-forming galaxies.', Astrophysical journal., 883 (2). p. 142.

Abstract

We have obtained three-dimensional maps of the universe in ~200 × 200 × 80 comoving Mpc3 (cMpc3) volumes each at z = 5.7 and 6.6 based on a spectroscopic sample of 179 galaxies that achieves gsim80% completeness down to the Lyα luminosity of $\mathrm{log}({L}_{\mathrm{Ly}\alpha }/[\mathrm{erg}\,{{\rm{s}}}^{-1}])=43.0$, based on our Keck and Gemini observations and the literature. The maps reveal filamentary large-scale structures and two remarkable overdensities made out of at least 44 and 12 galaxies at z = 5.692 (z57OD) and z = 6.585 (z66OD), respectively, making z66OD the most distant overdensity spectroscopically confirmed to date, with >10 spectroscopically confirmed galaxies. We compare spatial distributions of submillimeter galaxies at z sime 4–6 with our z = 5.7 galaxies forming the large-scale structures, and detect a 99.97% signal of cross-correlation, indicative of a clear coincidence of dusty star-forming galaxy and dust-unobscured galaxy formation at this early epoch. The galaxies in z57OD and z66OD are actively forming stars with star-formation rates (SFRs) gsim5 times higher than the main sequence, and particularly the SFR density in z57OD is 10 times higher than the cosmic average at the redshift (a.k.a. the Madau-Lilly plot). Comparisons with numerical simulations suggest that z57OD and z66OD are protoclusters that are progenitors of the present-day clusters with halo masses of ~1014 M ⊙.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.3847/1538-4357/ab2cd5
Publisher statement:© 2019. The American Astronomical Society. All rights reserved,
Date accepted:23 June 2019
Date deposited:30 October 2019
Date of first online publication:30 September 2019
Date first made open access:30 October 2019

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