Annual Report_Abridged - Second Version - FINAL

astrophysical phenomenon using computational techniques. This primary involves performing challenging high resolution simulations of astrophysical systems using high performance computing facilities. A key goal of these simulations is to produce realistic models of different systems, which can be directly compared with observed systems, to constrain the inherent physical models. To achieve these objectives, an important activity involves in- house development of novel computational techniques to address the numerical challenges for a modelling a given problem. In this regard, researchers at IUCAA have made two major contributions in the past year: a) Development of a novel parallel multi-grid Poisson solver for the widely used PLUTO MHD code, b) Running a suite of simulations of evaluate the impact of external turbulent magnetic field on the synchrotron and polarisation structure expected from young relativistic jets. The first project highlights the developmental capabilities of our research group, where the Poisson solver module opens up a wide variety of possibilities to explore many different astrophysical problems involving self- gravitational forces, with a particular focus on studying star formation in galactic and extra- galactic environments. Efforts have already been made to apply this module to investigate the impact of AGN driven winds on the star formation properties in dense turbulent clouds. The second project, highlights the importance of performing state of art high resolution simulations to understand the observational implications of AGN jets evolving in their immediate environment. It has been shown that external turbulent magnetic fields in the galaxy's halo can strongly depolarise the emerging synchrotron emission. 20 Top figure: Logarithmic total synchrotron emission, polarization fraction for a relativistic jet of power. Bottom figure: Same as above for jet in an environment with longer correlation lengths of magnetic field lines. TheCircumgalacticMedium In the modern theoretical paradigm of galaxy evolution, the circumgalactic medium (CGM) has been recognized as one of the key components for a comprehensive understanding of how galaxies acquire gas to fuel star formation and expel gas in the form of large-scale winds. Scientists at IUCAA are actively involved in understanding the properties of the CGM of galaxies for a wide range of redshifts. The research group led by Sowgat Muzahid at I UCAA ha v e d i s co v e r ed a s i gn i f i can t enhancement of cool, neutral gas in and around high redshift (z ~ 3) Lyman-alpha emitting galaxies (LAEs). This enhancement is even more pronounced when these galaxies are found in pairs or groups. In an interesting discovery, they identified a strong HI absorber in a quasar spectrum to be originating from cosmic