Abstract

During the first billion years of its life, the Universe has gone through one of its most remarkable phase changes, known as the Cosmic Dawn and the Epoch of Reionization (CD-EoR). This era constitutes a crucial missing chapter in the history of our Universe. This is the period when the very first sources of light were formed and where these sources heated and “re”-ionized the cold inter-galactic medium (IGM), consisting of mostly neutral hydrogen (HI) and helium (HeI). There are many fundamental questions related to this era that are still unresolved, including its exact timing and duration, the properties of these first light sources, etc. Answers to these questions will also enable us to understand how the present day cosmic structures have come into place from the tiny fluctuations in the matter and radiation of the early universe. This is why this era is also considered as one of the last frontiers of observational cosmology. Radio interferometric observations of the redshifted 21-cm signal, coming from the HI of this era, promise to resolve many of these puzzles. The present time is particularly exciting for this rapidly growing field, as several radio telescopes, such as the GMRT, LOFAR, MWA, PAPER, HERA, HIRAX, Tianlai, CHIME, OWFA etc., are competing to detect this signal from the CD-EoR as well as from the post-EoR phase of the Universe. The upcoming SKA, owing to its superior sensitivity, is expected to provide, for the first time, tomographic images of the HI distribution at different cosmic times. These images will enable a giant leap in our understanding of these mysterious chapters in the cosmic history. Additionally, experiments such as EDGES, LEDA, SARAS etc. are trying to measure the variation of the mean 21-cm signal with cosmic time. Further, an upcoming set of telescopes in other wavelengths (e.g. Euclid, Athena, WFIRST, JWST, ELT, TMT, SPHEREx, TIME, CONCERTO etc.) will have the capability to map and characterize the sources that might have reionized the Universe. These multi-wavelength future experiments promise to provide us a comprehensive picture of the CD-EoR through direct observations of the luminous sources as well as of their impact on the IGM at this period. To find innovative solutions to the various observational and technical obstacles faced by these new generation experiments and to analyze and interpret the unprecedented amount of observational data generated by them, we will need a large pool of highly skilled and motivated researchers. With this goal in mind, we are conducting a five-days-long school (27-31 January 2020) for Masters and PhD students, Postdocs, and Early Career Researchers who wish to conduct active research in this vibrant field. This school will consist of a series of lectures, hands-on demonstrations, and discussions by leading scientists on different methods of analytical modelling, simulations, observations, data reduction, and statistical inference for multi-wavelength observations of this early phase of our Universe. This will be part of the ongoing effort of the SKA-India consortium, which has been conducting such schools annually since 2016. The school will be preceded by an international conference (20-24 January 2020) that will focus on the progress and present status of observations, modelling, and statistical inference tools of the CD-EoR and post-EoR epoch.