Abstract
Recent observations support a significantly reduced visibility of Lyman-α (Lyα) flux from galaxies at redshifts z > 6. This is surprising considering that the visibility of Lyα flux has been observed to increase up towards z = 6. The goal of this thesis was to investigate and explore physical mechanisms other than reionization that could explain the demise of Lyα flux. We use the popular shell model to simulate the radiative transfer of photons escaping from a galaxy. We find the escape fraction to highly depend on the column density of hydrogen, the dust content, and the shell velocity. We specifically looked at emulating an evolution in the neutral fraction of hydrogen in the intergalactic medium (IGM) of XHI = 0.0 → 0.51 (corresponding to z = 6 → 7), and show that depending on the model it is possible to show that the reduction in Lyα flux can be explained by evolving gas kinematics. Finally we looked at models where this drop in Lyα flux is explained by a combination of evolving gas kinematics and an evolving IGM. We briefly present an outlook in which we discuss how future observations will put improved constraints on the Epoch of Reionization through observations of Lyα emitters.
Veileder: Førsteamanuensis Mark Dijkstra, Institutt for teoretisk astrofysikk, UiO
Intern sensor: Professor David F. Mota, Institutt for teoretisk astrofysikk, UiO
Ekstern sensor: Professor Garrelt Mellema, Stockholm University