Constraining Reionization with Lyman Alpha Emitting Galaxies

Understand

Neutral diffuse intergalactic gas that existed during the Epoch of Reionization (EoR) suppresses Lyman Alpha (Lya) flux emitted by background galaxies.

• In this chapter I summarise the increasing observational support for the claim that Lya photons emitted by galaxies at z>6 are suppressed by intervening HI gas.
• I describe key physical processes that affect Lya transfer during the EoR.
• I argue that in spite of the uncertainties associated with this complex multiscale problem, the data on Lya emitting galaxies at z=0-6 strongly suggests that the observed reduction in Lya flux from galaxies at z>6 is due to additional intervening HI gas.