A Lyman-α Galaxy at Redshift z = 6.944 in the COSMOS Field1

Lyman-α emitting galaxies can be used to study cosmological reionization, because a neutral intergalactic medium scatters Lyman-α photons into diffuse halos whose surface brightness falls below typical survey detection limits. Here we present the Lyman-α emitting galaxy LAE J095950.99+021219.1, identified at redshift z = 6.944 in the COSMOS field using narrowband imaging and followup spectroscopy with the IMACS instrument on the Magellan I Baade telescope. With a single object spectroscopically confirmed so far, our survey remains con-sistent with a wide range of IGM neutral fraction at z ≈ 7, but further obser-vations are planned and will help clarify the situation. Meantime, the object we present here is only the third Lyman-α-selected galaxy to be spectroscopically confirmed at z & 7, and is ∼ 2–3 times fainter than the previously confirmed z ≈ 7 Lyman-α galaxies. Subject headings: galaxies: high-redshift — dark ages, reionization, first stars 1