Dr. Rahul Kannan

The study of primitive stars and galaxies is an exciting new frontier in astrophysics and cosmology. They form within the first gigayear after the Big Bang and significantly impact their surroundings by emitting a lot of high-energy radiation that transforms the surrounding cold neutral gas into a hot and ionized medium. They form an important evolutionary link between the smooth matter distribution at early times and the highly complex structures seen today. Fortunately, a whole slew of instruments that have been specifically designed to study the high-redshift Universe (JWST, ALMA, Roman Space Telescope, HERA, SKA, CCAT-p, SPHEREx), have started providing valuable insights into high redshift structure formation and reionization. Therefore, theoretical/numerical models must achieve sufficient accuracy and physical fidelity to meaningfully interpret this new data. In this talk, I will introduce the THESAN simulation framework that is designed to efficiently leverage current and upcoming high redshift observations to constrain the physics of early galaxy formation. The multi-scale nature of the process is tackled by coupling large volume (~100s Mpc) simulations designed to study the large-scale statistical properties of the intergalactic medium (IGM) that is undergoing reionization, with high-resolution (~ 10 pc) simulations that zoom-in on single galaxies which are ideal for predicting the resolved properties of the primitive sources responsible for it. I will discuss applications from the first set of papers, including predictions for high redshift galaxy properties, the galaxy-IGM connection, Ly-a transmission and the back reaction of reionization on galaxy formation. I will finish by highlighting recent improvements to the model and proposed future work.