Rapid Decline of Lyman-alpha Emission Toward the Reionization Era

Understand

The observed deficit of strongly Lyman-alpha emitting galaxies at z>6.5 is attributed to either increasing neutral hydrogen in the intergalactic medium (IGM) and/or to the evolving galaxy properties.

• To investigate this, we have performed very deep near-IR spectroscopy of z>7 galaxies using MOSFIRE on the Keck-I Telescope.
• We measure the Lyman-alpha fraction at z~8 (combined photometric redshift peak at z=7.7) using two methods.
• First, we derived NLy{\alpha}/Ntot directly using extensive simulations to correct for incompleteness.