  We report the detection of the most luminous high-redshift Lyman Alpha
Emitting galaxy (LAE) yet seen, with log L(Ly alpha) = 43.9 ergs/s. The galaxy
-- COSMOS Lyman alpha 1, or COLA1 -- was detected in a search for
ultra-luminous LAEs with Hyper Suprime-Cam on the Subaru telescope. It was
confirmed to lie at z = 6.593 based on a Lyman alpha line detection obtained
from followup spectroscopy with the DEIMOS spectrograph on Keck2. COLA1 is the
first very high-redshift LAE to show a multi-component Lyman alpha line profile
with a blue wing, which suggests that it could lie in a highly ionized region
of the intergalactic medium and could have significant infall. If this
interpretation is correct, then ultra-luminous LAEs like COLA1 offer a unique
opportunity to determine the properties of the HII regions around these
galaxies which will help in understanding the ionization of the z ~ 7
intergalactic medium.

Astrophysics of Galaxies;Cosmology and Nongalactic Astrophysics