Subaru Deep survey. IV. Discovery of a large-scale structure at redshift ≃5

K. Shimasaku, M. Ouchi, S. Okamura, N. Kashikawa, M. Doi, H. Furusawa, M. Hamabe, T. Hayashino, K. Kawabata, M. Kimura, K. Kodaira, Y. Komiyama, Y. Matsuda, M. Miyazaki, S. Miyazaki, F. Nakata, K. Ohta, Y. Ohyama, M. Sekiguchi, Y. ShioyaH. Tamura, Y. Taniguchi, M. Yagi, T. Yamada, N. Yasuda

Research output: Contribution to journalArticlepeer-review

111 Citations (Scopus)


We report the discovery of a large-scale structure of Lyα emitters (LAEs) at z = 4.86 based on wide-field imaging with the prime-focus camera (Suprime-Cam) on the Subaru Telescope. We observed a 25′ 45′ area of the Subaru Deep Field in a narrow band (NB711, λc = 7126 Å and FWHM = 73 Å) together with R and i′. We isolate from these data 43 LAE candidates down to NB711 = 25.5 mag using color criteria. Follow-up spectroscopy of five candidates suggests the contamination by low-z objects to be ∼20%. We find that the LAE candidates are clustered in an elongated region on the sky of 20 Mpc in width and 50 Mpc in length at z = 4.86, which is comparable in size to present-day large-scale structures (we adopt H0 = 70 km s-1 Mpc-1, Ω0 = 0.3, and λ0 = 0.7). This elongated region includes a circular region of 12 Mpc radius of higher surface overdensity (δΣ = 2), which may be the progenitor of a cluster of galaxies. Assuming this circular region to be a sphere with a spatial overdensity of 2, we compare our observation with predictions by cold dark matter models. We find that an Ω0 = 0.3 flat model with σ8 = 0.9 predicts the number of such spheres consistent with the observed number (one sphere in our survey volume) if the bias parameter of LAEs is b ≃ 6. This value suggests that the typical mass of dark halos hosting LAEs at z ≃ 5 is of the order of 1012 M. Such a large mass poses an interesting question about the nature of LAEs.

Original languageEnglish
Pages (from-to)L111-L114
JournalAstrophysical Journal
Issue number2 II
Publication statusPublished - 2003 Apr 1
Externally publishedYes


  • Cosmology: observations
  • Early universe
  • Galaxies: evolution
  • Galaxies: high-redshift
  • Galaxies: photometry
  • Large-scale structure of universe

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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