IUCAA Brochure 2024

Dwarf galaxies The resolving power of Astrosat’s UltraViolet Imaging Telescope and AstroSat UV Deep Field (AUDF) imaging has been the key to spotting such extremely blue, young star- forming clumps that in-spiral inside the optical boundary within a billion years (much shorter than a galaxy's lifetime) timescale to grow these galaxies. One of the key challenging Giant galaxies, like our Milky Way and its neighbor Andromeda, are surrounded by tens of dwarf galaxies - irregular in shape and often forming stars. Looking back in time, we see that galaxies were smaller and more irregular. How these dwarf galaxies assemble their stars and evolve is still one of the outstanding questions of galaxy formation. A recent study using AstroSat shows how the star-forming clumps in the outskirts of a dwarf galaxymigrate towards the central region due to dynamical friction and contribute to its growth inmass and luminosity. The discovery of this process in several dwarf galaxies has been made for the first time by a group of IUCAA researchers in collaboration with Indian university students and international scientists. tasks has been to establish the detection of these. Another key research activity of the Galaxy group at IUCAA is to search for extended UV emission in the outskirts of dwarf galaxies, some of which are seen now at a stage when our universe was less than half its current age. In parallel, the group is actively hunting for such distant dwarf galaxies (at redshift z>1) that might have contributed to the reionization history of the universe.