Astronomy seminar - Tomographic studies of 21-cm signal during reionization

The formation of the first luminous sources in the Universe, such as the first generation of stars and accreting black holes, led to the ionization of hydrogen gas present in the intergalactic medium (IGM). This period in which the Universe transitioned from a cold and neutral state to a predominantly hot and ionized state is known as the Epoch of Reionization (EoR). The EoR is one of the least understood epochs in the Universe’s evolution mostly due to the lack of direct observations. We can probe the reionization process with the  21-cm signal, produced by the spin-flip transition in neutral hydrogen. However, current radio telescopes have not been able to detect this faint signal. The low-frequency component of the Square Kilometre Array (SKA-Low), will be sensitive enough not only to detect the 21-cm signal produced during EoR but also to produce images of its distribution on the sky. A sequence of such 21-cm images from different redshifts will constitute a three-dimensional, tomographic, data set. Before the SKA comes online, it is prudent to develop methods to analyse these tomographic images in a statistical sense. In this seminar, I will describe the EoR information encoded in the 21-cm signal and present the tomographic analysis methods that will be useful to decode this information.