Discovery of a giant Lyα emitter near the reionization EPOCH

Masami Ouchi, Yoshiaki Ono, Eiichi Egami, Tomoki Saito, Masamune Oguri, Patrick J. McCarthy, Duncan Farrah, Nobunari Kashikawa, Ivelina Momcheva, Kazuhiro Shimasaku, Kouichiro Nakanishi, Hisanori Furusawa, Masayuki Akiyama, James S. Dunlop, Angela M.J. Mortier, Sadanori Okamura, Masao Hayashi, Michele Cirasuolo, Alan Dressler, Masanori IyeMatt J. Jarvis, Tadayuki Kodama, Crystal L. Martin, Ross J. McLure, Kouji Ohta, Toru Yamada, Michitoshi Yoshida

Research output: Contribution to journalArticlepeer-review

136 Scopus citations


We report the discovery of a giant Lyα emitter (LAE) with a Spitzer/Infrared Array Camera (IRAC) counterpart near the reionization epoch at z = 6.595. The giant LAE is found from the extensive 1 deg2 Subaru narrowband survey for z = 6.6 LAEs in the Subaru/XMM-Newton Deep Survey (SXDS) field, and subsequently identified by deep spectroscopy of Keck/DEIMOS and Magellan/IMACS. Among our 207 LAE candidates, this LAE is not only the brightest narrowband object with L(Lyα) = 3.9 ± 0.2 × 1043 erg s-1 in our survey volume of 106 Mpc3, but also a spatially extended Lyα nebula with the largest isophotal area whose major axis is at least ≃3″. This object is more likely to be a large Lyα nebula with a size of ≳17 kpc than to be a strongly lensed galaxy by a foreground object. Our Keck spectrum with medium-high spectral and spatial resolutions suggests that the velocity width is v FWHM = 251 ± 21 km s-1, and that the line-center velocity changes by ≃60 km s-1 in a 10 kpc range. The stellar mass and star formation rate are estimated to be 0.9-5.0 × 1010 M and >34 M yr-1, respectively, from the combination of deep optical to infrared images of Subaru, UKIDSS-Ultra Deep Survey, and Spitzer/IRAC. Although the nature of this object is not yet clearly understood, this could be an important object for studying cooling clouds accreting onto a massive halo, or forming-massive galaxies with significant outflows contributing to cosmic reionization and metal enrichment of intergalactic medium.

Original languageEnglish (US)
Pages (from-to)1164-1175
Number of pages12
JournalAstrophysical Journal
Issue number2
StatePublished - May 10 2009


  • cosmology: observations
  • galaxies: formation
  • galaxies: high redshift

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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