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The Epoch of Reionization (EoR) is one of the least understood chapters
in the history of our Universe. The formation of the first luminous sources
initiated the transition of the cold and neutral intergalactic medium (IGM)
into a hot and ionized state.
The redshifted 21-cm signal from the IGM neutral hydrogen is the most
promising probe of the EoR. This directly probes the ionization and
thermal states of the IGM during that period. In particular, the distribution
of the ionized regions around the first sources introduces scale-dependent
features in the spherically averaged EoR 21-cm signal power spectrum.
In recent times, radio telescopes such as LOFAR, NenuFAR, MWA, and HERA
have produced useful upper limits on the 21-cm signal power spectrum
which have already started constraining the EoR scenarios. In this seminar,
I will talk about the potential of this probe, its observation status, and our present
understanding of the Universe's first billion years from this probe. |