Probing early Universe through redshifted 21-cm signal: Modeling and observational challenges

Cosmic dawn (CD) and the epoch of reionization (EoR) are most important parts cosmic history during which first luminous structures emerged. These objects heated ionized neutral atomic hydrogen in intergalactic medium. The redshifted 21-cm radiation from provides an excellent direct probe to study evolution (Hi) thus reveal nature objects, their role this last phase transition Universe formation thereafter. Direct mapping Hi density CD–EoR is rather difficult with current forthcoming instruments due stronger foreground other observational contamination. detection signal expected be done through statistical estimators. Given upmost importance analysis signal, physics considered as one objective upcoming SKA-low telescope. This paper summarizes collective effort Indian astronomers understand origin sources ionizing photons, propagation IGM, various cosmological effects on measures like power spectrum, bispectrum, etc. A such by developing estimators rigorous assessment uncertainties, challenges that large emission calibration issues also discussed. Various versions methods discussed here have been used practice Giant Meterwave Radio Telescope successful contamination upper limits matter post-reionization era. efforts compiled has a part global prepare proper technique, procedure for light SKA-low.