IUCAA - Khagol # 129 - Oct 2022 - English

| KHAG L | No. 129 - OCTOBER 2022 | 08 Astrosat - opening new avenues for young researchers - Kanak Saha Galaxies are the basic building blocks of the Universe- they come in all sizes. Our galaxy, the Milky Way, is one of the giant galaxies- with billions of stars, but little current star formation. Giant galaxies such as ours are surrounded by tens of dwarf galaxies- irregular in shape, often forming stars. As we look backwards in time we see that galaxies were smaller and more irregular (since light takes time to travel, a galaxy seen 3 billion light-years away from a Universe that is 3 billion years younger). How these dwarf and giant galaxies assemble their stars and evolve into modern-day galaxies, like our own Galaxy, the Milky way is still one of the major puzzles. A recent study by a teamof scientists using AstroSat (India's first dedicated multi- wavelength space observatory) shows how the star-forming complexes in the outskirts of a dwarf galaxymigrate towards the central region and contribute to its growth in mass and luminosity. This process that is now witnessed in several dwarf galaxies is a very important link in understanding the bigger picture of galaxy growth and evolution. Anshuman Borgohan, a young research scholar at Tezpur University, Assam working under the guidance of Prof. Rupjyoti Gogoi (Supervisor), Tezpur University, Assam and Prof. Kanak Saha (Co-Supervisor), Professor of Astronomy, at the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune, along with an international team of astronomers from India, the USA and France, led by Prof. Saha, contributed significantly to the field of low mass galaxies also known as Blue Compact Dwarf Galaxies (BCDs). These BCDs consist of huge clusters of young stars. His Research Highlights at IUCAA findings, which are a part of his PhD thesis, show how the star-forming complexes in the outskirts of a dwarf galaxy migrate towards the central region and contribute to its growth in mass and luminosity. This process, which the researchers have witnessed in several dwarf galaxies, is a very important link in understanding the bigger picture of galaxy growth and evolution. The article has been published on 20th July 2022 by the Nature journal, which is the world's leading multidisciplinary science journal. “ It is quite overwhelming actually “ expressed the young astronomer whose efforts have been recognized by the scientific community. He also added that “Capturing the assembly process in dwarf galaxies is believed to be one of the important links to complete the picture of galaxy growth and evolution. AstroSat/UVIT has been a remarkable addition to the list of UV observatories to date and has opened up promising windows to probe the understanding of the galaxy assembly process”. Prof. Kanak Saha, who conceptualised the research has his primary research focused on how galaxies form in the early universe and how they evolve into present-day ones. He hasmade a breakthrough discovery of a faint galaxy at high redshift, detected by deep observations using India's first space observatory, AstroSat, for which he was awarded the Shanti Swarup Bhatnagar Prize for Science and Technology in the physical sciences category. His recent works throw light on the formation of long- standing spiral structures and dynamics of galaxies. Prof. Rupjyoti Gogoi from Tezpur University, Assam, who is an associate u n d e r t h e I UC A A a s s o c i a t e s h i p Programme, studies interstellar dust in Milky Way and nearby galaxies from observational data. She also works on Extragalactic astronomy, where she studies the structure and evolution of other galaxies. She is a part of the associateship progr amme a t IUCAA wor k i ng i n collaboration with researchers in IUCAA on the study of the variability of Blazars, the Wali through his researches has made Indian academics (teachers and students) aware of the contributions of early Indian scientists, thereby improving their awareness of their heritage. On a personal note, I had the pleasure and privilege of knowing Kamesh Wali from my school days at the Banaras Hindu University. He usually visited India every year and had interaction with Indian scientists. He was ever interested in knowing, learning something new and as such he was a student at heart. I had attended some of his general talks which were entertaining and informative. Back home, both Kashi and Kamesh were a hospitable couple especially for visiting scientists. My wife and I enjoyed the warm hospitality at Chez Wali when we discussed Chandra, Bose, our BHU days and of course Indian cricket.