Modern cosmology mainly deals with the origin and evolution of the Universe. Various observational detections (e.g., CMBR, galaxy survey) probe the Universe at different stages of time. The 21-cm signal from neutral hydrogen is another important tool that can be used to study the Universe over a large time period. It also contains a wealth of cosmological and astrophysical information. But, the problem is particularly challenging due to the presence of strong foregrounds. In this talk, I will present the global effort toward the detection of this faint signal using radio telescopes. We have also developed a novel estimator (namely Tapered Gridded Estimator: TGE) to detect this 21-cm signal in the presence of strong foreground sources. I will discuss the formalism and the effectiveness of the TGE, which is relevant for the present and future 21-cm studies.
Dr. Samir Choudhuri is an Assistant Professor and a member of the Gravitation and Cosmology Group at the Indian Institute of Technology Madras. Before that, he was a Post-Doctoral Fellow at the Astronomy Unit, Queen Mary University of London till 2022, and worked with Dr. Philip Bull to study the early Universe using 21-cm radiation with the Hydrogen Epoch of Reionization Array (HERA). He was also a Post-Doctoral Fellow at National Centre for Radio Astrophysics NCRA- TIFR, India, from 2016-2019. He is an active member of several radio astronomy groups e.g. the GMRT, the HERA, and the SKA. He did Ph.D. at the Indian Institute of Technology, Kharagpur, in 2016 under the supervision of Prof. Somnath Bharadwaj and Dr. Sk. Saiyad Ali. He received his M.Sc in Physics from Jadavpur University, Kolkata, in 2011.