Abstract
Cosmic reionization represents a crucial phase in the evolution of the Universe, with galaxies playing a central role in driving this process. Understanding how galaxies form, reionize the Universe, and evolve over cosmic time remains a major astrophysical challenge. In this talk, we present recent findings that address these fundamental questions, with a focus on the nature of star formation in the first galaxies and its impact on reionization. While traditional models have suggested that faint, undetected galaxies were the primary sources of ionizing photons, our research shows that galaxies experiencing bursts of star formation, which are relatively brighter, are actually the major contributors to reionization. This conclusion is supported by recent observations from the James Webb Space Telescope (JWST) and the detection of escaping Lyman continuum radiation from starburst galaxies—rare at low redshift but ubiquitous at high redshift. Additionally, by comparing JWST observations with EAGLE cosmological simulations, we identify the dark matter halos that host these bursty galaxies. Our results suggest that halos with masses ≥ 10^9 M⊙ were essential in reionizing the Universe, with more massive halos accelerating reionization between redshifts z ≈ 8 and 6. Additionally, we present a new galaxy formation model based on an analogy with main sequence stars in virial equilibrium, enabling us to reproduce key galactic properties such as star formation rates and mass-metallicity relations over cosmic time. These findings deepen our understanding of the role of bursty star formation and halo evolution in both reionization and galaxy formation after the advent of JWST.
About Speaker
Dr. Mahavir Sharma is an assistant professor of physics at the Indian Institute of Technology (IIT) Bhilai since 2020. He did his PhD from Raman Research Institute, Bengaluru, in 2014. For the next 4 years, he was a postdoctoral researcher at the Institute for Computational Cosmology, Durham University, UK. Before joining IIT Bhilai, he was in Perth, Australia, as an independent postdoctoral fellow at the Centre of Excellence for all-sky Astrophysics in three dimensions (ASTRO-3D).
His research interests are in the area of computational hydrodynamics and astrophysics. He has worked on broad research topics such as galactic outflows driven by various scenarios: supernovae, AGN, or radiation and its implications for the structure formation. He has also investigated the evolution of metals in our galaxy and its connections with the stellar populations. In recent years, he has focused on the reionization problem, and he will describe how our understanding of galaxy formation is evolving after the recent JWST observations.
