fraction in the intergalactic medium at the end of the reionization epoch, although our weak evidence suggests the need for a larger statistical sample to allow for a more robust conclusion.'
author:
- 'Mimi Song, Steven L. Finkelstein, Rachael C. Livermore, Peter L. Capak, Mark Dickinson, and Adriano Fontana'
title: 'Keck/MOSFIRE Spectroscopy of $\lowercase{z}=$ 7–8 Galaxies: L$\alpha$ Emission from a Galaxy at $\lowercase{z} = 7.66$'
---

Introduction
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The Ly$\alpha$ emission line is a unique tool as the line properties encode information about the scattering medium through which the photons have passed. During the past few years, in the present absence of a sensitive 21 cm signal from reionization, investigating the redshift evolution of the “Ly$\alpha$ fraction”, the fraction of Lyman-break galaxies (LBGs) which exhibit strong Ly$\alpha$ emission, has served as a valuable and feasible means of providing constraints on the ionization state of the intergalactic medium (IGM). Spectrosopic follow-up of LBGs has revealed that the Ly$\alpha$ fraction (typically defined as LBGs with rest-frame Ly$\alpha$ EW $> 25$ Å) steadily increases from $z=3$ to $z=6$, reaching $\sim$50% for faint galaxies ($M_{\rm UV} > -20.25$) at $z \sim 6$ [@stark10; @stark11]. At higher redshifts of $z \sim 7$, however, initial expectations 