| Abstract : | Galaxies are the building blocks of the Universe. How they form, how they reionize the Universe and how they evolve subsequently are outstanding problems in astrophysics. This talk presents an overview and our recent work on these problems. The formation of the first galaxies and their role in reionization is hotly debated. The nature of star formation in first galaxies is a key to understand the process of reionization. Traditional viewpoint based on an extrapolation of luminosity functions has been that a major part of the photon budget required for reionization was provided by the faintest galaxies yet undetected, however this is debatable. The scatter in star formation rates at high redshift is as important as the smooth luminosity functions. Our investigation shows that galaxies with a bursty star formation are relatively brighter and provide the majority of ionizing photons required for reionization. This is confirmed now by the JWST and is supported by observations of the escaping Lyman continuum from a few nearby starburst galaxies, which are rare at low redshift but ubiquitous at high redshift. Further, we have developed a model for the evolution of galaxies post-reionization. This model enables us to reproduce galactic properties, such as star formation rates, stellar mass function, and mass-metallicity relation, by building on an analogy with the evolution of main sequence stars that obey virial equilibrium. |
