Dr. Rajesh Mondal

Neutral hydrogen (HI) is a powerful tracer of the Universe, persisting for much of its cosmic history. The redshifted 21-cm signal due to the hyperfine transition of HI is a promising method to study its three-dimensional distribution. The first billion years of cosmic history mark the formation of the first stars and galaxies. After years of theoretical predictions, a considerable international effort is now producing the first tentative results from experiments such as EDGES, SARAS, GMRT, LOFAR, MWA, and HERA. The coming theory and observations will reveal the mysterious era of cosmic dawn and reionization, including the properties of the first stars and galaxies, and possibly more exotic discoveries. There are also plans to probe the pre-stellar "Dark Ages" with telescopes on the moon. I will summarize and update current studies of 21-cm cosmology and the Epoch of Reionization. I will discuss the challenges and opportunities of these studies, and highlight some of our most recent results.