Observational Signatures of Lyman Alpha Emission from Early Galaxy Formation.

Abstract

The next generation of telescopes aim to directly observe the first generation of galaxies that initiated the reionization process in our Universe. The Lyα 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 Lyα 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 of the key uncertainties in interpreting existing LAE observations relates to the impact of the ionized IGM on Lyα 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 Lyα spectral line shape such that > 5% of the emitted Lyα 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.