Constraining Reionization with Lyman Alpha Emitting Galaxies

TL;DR

This paper reviews how observations of Lyman Alpha emitting galaxies support the idea that the Epoch of Reionization's neutral hydrogen gas suppresses Lya flux, and discusses future surveys to better constrain reionization.

Contribution

It synthesizes observational evidence and physical processes to argue that increased HI gas causes Lya flux suppression at high redshift, and highlights future survey prospects.

Findings

Lya flux suppression correlates with increased HI gas during EoR

Current data strongly suggest additional HI gas causes flux reduction at z>6

Upcoming surveys will significantly reduce observational uncertainties

Abstract

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. The main question is what fraction of this additional HI gas is in the diffuse neutral IGM. I summarise how future surveys on existing and upcoming instruments are expected to reduce existing observational uncertainties enormously. With these improved data we will likely be able to nail down reionization with Lya emitting galaxies.