Annual Report_Abridged - Second Version - FINAL

16 around galaxies at redshifts, z<2. Diffuse gas is detected in absorption in the spectra of two background quasars at z~2-3, which are two of the few currently known quasars with multiple images due to strong gravitational lensing by galaxy clusters at z~0.5-0.6. The angular separations between different pairs of quasar multiple images enabled to probe the absorption over transverse physical separations of ~0.4-150 kpc. The integral field spectroscopic observations of these quasar fields using Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT) facilitated study of the galaxies associated with the absorbing gas. The results indicate that the metal-enriched gaseous structures around galaxies become less coherent with distance, with a likely coherence length scale of ~10 kpc. Science from MeerKAT Absorption Line Survey (MALS) The vast expanse of the observable universe is home to countless galaxies. Many of these galaxies have supermassive black holes (SMBHs), which become active when gas infalling towards the black hole results in release of large amounts of energy. The energy output from these Active Galactic Nuclei (AGN), often outshines the light from the entire galaxy. Additionally, they eject "jets": collimated streams of highly-energetic ionized gas particles, piercing through the interstellarmedium(ISM) amid the stars. The interplay between energetic output from AGN and cold gas in host galaxies is central to understanding the fuelling of massive black holes and the evolution of galaxies hosting these. MALS is carrying out a sensitive search of absorption disk changes its structure and forms a warm mediumproducing soft X-ray excess emission. As part of an international collaboration, IUCAA researchers observed with AstroSat's Soft X-ray Telescope, and helped unravel amysterious super bright flash with fast variability, to be a tidal disruption event in which an SMBH in a distant galaxy captured a star and produced a relativistic jet which pointed towards the earth, which producedmore light than a 1000 trillion Suns. In a study of a transient black hole X-ray binary MAXIJ1820+070, IUCAA scientists find changes in the inner radius of the accretion disk associated with changes in the structure of and emission from the hot Corona. This study further revealed a captivating connection between the X-ray emission from the inner regions near the black hole and optical/UV emission from the outer region of the accretion disk. In another research data from AstroSat's Cadmium Zinc Telluride Imager (CZTI), reported around 24% polarised high energy X-rays from the black hole X-ray binary Cygnus X-1. This is much higher than the expected less than 10%, thus hinting that the mechanism of X-ray emission (more energetic than 200 keV) is from the jet, possibly synchrotron radiation in an ordered magnetic field. Moreover, the CZTI detected high X-ray polarisation only in the state that exhibits strong radio emission from the jet. For the first time, therefore, one can confirm the direct connection of the hard X-ray emission to the relativistic jet. ProbingCoherence inMetal Absorption Rajeshwari Dutta and her collaborators recently conducted a unique tomographic analysis of the structure of metal-enriched cool gas in the halos