MSV-2035 Astronomy Document - Inside Design - FINAL - FINAL

perturbations at very large scales. The earliest observable Universe (using the thermal fluctuations in the Cosmic homogeneous and isotropic with very tiny fluctuations (i.e., weaker Microwave Background Radiation, CMBR) is 5 than 1 part in 10 ). However, the present-day Universe is inhomogeneous and filled with highly complex structures (filaments, sheets, clusters and voids) with large variations in density at smaller scales (i.e < 300 million light-year). Understanding how these structures form and evolve from the initial tiny fluctuations to what we see today is the big challenge facing the cosmology community. While the inflationary scenario does provide the tiny initial density and velocity fluctuations from which the galaxies, clusters, voids and the grand cosmic web that we observe originated, there is muchmore to be explored and explained. Due to cosmic expansion (Hubble flow), photons from distant objects are redshifted with respect to the emitted wavelengths. Thus, bymeasuring the shifts in the wavelength of spectral lines we are able to estimate distances of very far away objects. This, coupled with the finite light travel time allows us to directly observe the evolution of the Universe from very early stages. While we have been developing a consistent sequence of events that has led to the present-day Universe starting from moments after Big Bang, precision measurements are needed to lift the degeneracy in our understanding. There are important questions in this framework that remain unsolved and the questions that we seek answers for are: What were the initial conditions for our Universe and how did they originate? Is the Universe statistically isotropic and homogeneous?What is the large scale topology of the Universe?What is the origin and evolution of cosmic magnetism? Can one measure the mass of neutrinos from their imprint on the large scale structures? How and when did the first sets of stars and galaxies form? What physics governs the formation and evolution of stars from primordial gas? When and how did the Universe get reionised and what is the nature of the dominant sources of reionising radiation? How andwhen did the first generation of supermassive black holes (SMBH) form?At what stage, and how is the connection between SMBH and host galaxy properties established? 2.3 Galaxy Formation andLarge Scale Structure While the dynamics of the Universe is governed by the “dark matter” and “dark energy”, observationally, we use galaxies as the tracers of the matter distribution in our Universe. Galaxies are formed in gravitational potentials of halos of dark matter particles. The star formation in galaxies are related to the efficiencies of gas cooling, fragmentation and subsequent gravitational collapse. They are also influenced by various feedback processes related to gas flows, turbulence, shocks, cosmic rays and magnetic field. It is now well established that in addition to stars, galaxies have gas in the regions between stars (interstellar medium, ISM) and in the circumgalactic medium (CGM, an extended region in a galaxy far beyond the region occupied by stars). Thus, the evolution of galaxies is governed by the evolution of all its constituents like stars, CGM and ISM and the interactions between them. It is also now well established that most of the baryons (normal matter which constitutes material around us) produced in the Big Bang reside in regions between galaxies (i.e so called intergalactic medium, IGM) in the early Universe. However, in the present-day Universe a substantial fraction of these baryons are incorporated into galaxies and clusters of galaxies. Thus, understanding the flow of matter at different scales and processes guiding this flow are essential to our understanding of formation and evolution of large scale structure in our Universe. Specifically, one would like answers to the following questions using deep observations. How do galaxies form and evolve across the cosmic time?What is the connection between stars, gas and the underlying dark matter distribution? What triggers the formation of the quasar (or active galactic nuclei, AGN) phase in a galaxy and what controls its duty Astronomy & Astrophysics 14 MEGA SCIENCE VISION-2035