First Spectroscopic Confirmations of z ∼ 7.0 Lyα Emitting Galaxies in the LAGER Survey

Weida Hu, Junxian Wang, Zhen Ya Zheng, Sangeeta Malhotra, Leopoldo Infante, James Rhoads, Alicia Gonzalez, Alistair R. Walker, Linhua Jiang, Chunyan Jiang, Pascale Hibon, L. Felipe Barrientos, Steven Finkelstein, Gaspar Galaz, Wenyong Kang, Xu Kong, Vithal Tilvi, Huan Yang, Xianzhong Zheng

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


Narrowband imaging is a highly successful approach for finding large numbers of high-redshift Lyα emitting galaxies (LAEs) up to z ∼ 6.6. However, at z ≳ 7 there are as of yet only three narrowband selected LAEs with spectroscopic confirmations (two at z ∼ 6.9-7.0, one at z ∼ 7.3), which hinders extensive studies on cosmic reionization and galaxy evolution at this key epoch. We have selected 23 candidate z ∼ 6.9 LAEs in COSMOS field with the large area narrowband survey Lyman-Alpha Galaxies at the End of Reionization (LAGER). In this work, we present spectroscopic follow-up observations of 12 candidates using the Inamori Magellan Areal Camera and Spectrograph on Magellan. For nine of these, the observations are sufficiently deep to detect the expected lines. Lyα emission lines are identified in six sources (yielding a success rate of 2/3), including three luminous LAEs with Lyα luminosities of L Lyα ∼ 1043.5 erg s-1, the highest among known spectroscopically confirmed galaxies at ≳7.0. This triples the sample size of spectroscopically confirmed narrowband selected LAEs at z ≳ 7, and confirms the bright-end bump in the Lyα luminosity function we previously derived based on the photometric sample, supporting a patchy reionization scenario. Two luminous LAEs appear physically linked with a projected distance of 1.1 pMpc and velocity difference of ∼170 km s-1. They likely sit in a common ionized bubble produced by themselves or with close neighbors, which reduces the intergalactic medium attenuation of Lyα. A tentative narrow N v λ1240 line is seen in one source, hinting at activity of a central massive black hole with metal-rich line-emitting gas.

Original languageEnglish (US)
Article numberL16
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Aug 20 2017


  • cosmology: observations
  • dark ages, reionization, first stars
  • galaxies: formation
  • galaxies: highredshift

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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