Observational Signatures of Lyman Alpha Emission from Early Galaxy Formation

TL;DR

This paper discusses how Lyman Alpha emission from early galaxies can be used to probe the Epoch of Reionization, emphasizing the importance of understanding scattering effects and observational strategies to interpret high-redshift galaxy data.

Contribution

It highlights the role of galactic outflows and scattering in interpreting Lyman Alpha signals and outlines necessary steps to improve understanding of early galaxy observations.

Findings

Scattering through galactic outflows can transmit >5% of Lya radiation through a neutral IGM.

Lyman Alpha emission is a key spectral feature for studying high-redshift galaxies.

Understanding IGM effects is crucial for interpreting LAE observations during reionization.

Abstract

The next generation of telescopes aim to directly observe the first generation of galaxies that initiated the reionization process in our Universe. The Lyman Alpha (Lya) emission line is robustly predicted to be the most prominent intrinsic spectral feature of these galaxies, making it an ideal target to search for and study high-redshift galaxies. I briefly discuss why Lya emitting galaxies (LAEs) provide a good probe of the intergalactic medium (IGM) during the Epoch of Reionization (EoR). I argue that if we wish to fully exploit LAEs as a probe of the EoR, it is important to understand what drives their observed redshift evolution after reionization is completed. One important uncertainty in interpreting existing LAE observations relates to the impact of the ionized IGM on Lya photons emitted by galaxies, which is strongly connected to the effects of scattering through HI in galactic outflows. Scattering through galactic outflows can also modify the Lya spectral line shape such that > 5% of the emitted Lya radiation is transmitted directly to the observer, even through a fully neutral IGM. Finally, I discuss what is required --observationally and theoretically-- to resolve the uncertainties that affect existing interpretations of data on LAEs.