Lyman Alpha Radiative Transfer through Galactic Outflows: Astrophysical & Cosmological Implications

Lyman alpha emitting galaxies have been observed out to redshift greater than six, and are interesting for many reasons. In this talk I will focus on two: Firstly I will discuss why LAEs provide us with a unique glimpse of the Universe when it was less than a Billion years old. Secondly, I will talk about the `Hobby-Eberly Dark energy experiment’ (HETDEX), which is planning to measure the large scale structure of the Universe to do precision cosmology with ~ 1 million LAEs at z=1.9-3.5. To fully exploit these observations requires a proper understanding of radiative transfer of Lyman alpha photons through both the interstellar and intergalactic medium. After a brief introduction to the basics of Lya transport, I will argue that there are strong observational indications that Lya photons are affected by (possibly sub kpc) galactic outflows. This plausible connection between has two interesting implications: (i) it may be significantly easier to detect Lyman alpha photons from galaxies even when the Universe were mostly neutral, and (ii) it weakens so-called `non-gravitational effects’ on the large scale clustering of LAEs. Understanding of propagation of Lya photons through outflows is therefore important, and we are taking the first steps in that direction. I will show some preliminary results of Lya RT through (dusty) clumpy outflows.