Constraining temperature fluctuations in the IGM with Lyα forest at 4 < z < 5

Abstract

The Epoch of Reionization (EoR) marks as a key phase transition event in the evolution of the Universe. During EoR the first star-forming galaxies, with the emission of UV radiation, ionize the neutral hydrogen present in the intergalactic medium (IGM). Several studies have suggested that this process was extended and inhomogeneous in nature. The denser regions in the Universe collapsed first, forming bright sources that ionized their surroundings, heating up the gas to large temperatures. Whereas, less dense regions remained neutral and cool till longer time. The difference in the timing of ionization of different regions produces spatial temperature fluctuations in the IGM during the end stages of reionization that continue to persist even shortly after hydrogen reionization. The objective of the thesis is to probe and constrain these temperature fluctuations induced by inhomogeneous reionization. We work with high resolution simulations, designed to produce controlled temperature fluctuations in the IGM using different reionization histories and temperature for inhomogeneous reionization of the hydrogen.