Soon after the Cosmic Dark Age, our universe transformed from neutral to ionized. Today, most of the matter between galaxies is ionized. It is believed that the extreme UV photons emitted by the first galaxies were responsible for the reionization of our universe. However, the nature of such galaxies remains elusive. In this talk, I plan to report the first discovery of a high-redshift galaxy, AUDFs01, emitting extreme UV photons at rest-frame 600 Angstrom. AUDFs01 is the first such galaxy from the AstroSat UV deep field that was created based on observation carried out by the Ultraviolet Imaging Telescope on AstroSat. The detection of extreme UV photons from distant galaxieswould open up a new window to constrain the shape of the ionizing spectrum.

Prof. Kanak Saha is an associate professor of astrophysics at Inter-University Centre for Astronomy and Astrophysics (IUCAA). Prof. Saha graduated from Scottish Church College in 1998 and pursed his M.Sc. from Banaras Hindu University in 2001. He earned his Ph.D. degree in 2008 from Indian Institute of Science, Bengaluru. He then moved to Academia Sinica, Geneva Observatory in Switzerland as a Post Doctoral Fellow. Prior to joining IUCAA, he was a Humbold fellow at MPE, Munich, Germany. His present research interests include formation of galaxies in the early universe and their evolution. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology for his contributions to physical sciences in 2021.