Title: Stellar Populations in the Milky Way, a theoretical perspective

Abstract: At the beginning of the Universe, the Big Bang, only light elements such as hydrogen, helium, and lithium are formed. Elements heavier than carbon are formed only in stars and are distributed into the cosmos when the stars die. Among them, so-called alpha elements (O, Mg, Si, S, and Ca) are produced by core-collapse supernova explosions of massive stars, while iron-peak elements are produced predominantly by Type Ia supernovae - thermonuclear explosions of binary star systems. Elements heavier than iron are formed by neutron-capture processes.
Stars are fossils that retain the history of their host galaxies. At the end of their lives, some explode as supernovae, producing heavy elements that are distributed into the interstellar medium. New stars created from this gas contain elements produced by the previous generations of stars. From the spatial distribution of elements, it is therefore possible to constrain the formation and evolutionary histories of the galaxies. This approach, Galactic Archaeology, has been popularly used for our Milky Way Galaxy. It can also be applied to external galaxies thanks to the recent and future observations with integral field units.
My team has been running hydrodynamical simulations from cosmological initial conditions including detailed chemical enrichment. First of all, I will show how elemental abundances (from C to U) evolve in a zoom-in simulation of Milky Way-type galaxy, comparing with the observations in the Milky Way. Then I will discuss the origins of the substructures, e.g., the halo, bulge, and thin and thick discs. Finally, I will predict the role of gas infall, outflow, radial flow, and stellar migration in the Milky Way-type galaxy, linking to the future observations with JWST.

Bio: I am a Reader in Astrophysics at the University of Hertfordshire, specializing in the chemical evolution of galaxies as well as supernova physics, nucleosynthesis, and the origin of elements. I am interested in the fact that stars are born and die in galaxies and keep changing the chemical composition of the galaxies, which can be used as a fossil record to investigate the history of the galaxies (galactic archaeology). I have been running hydrodynamical simulations of galaxies including detailed chemical enrichment (called chemo-dynamical simulations) to predict the spatial distribution of elements in the Universe across cosmic time, beyond the reach of even the best telescopes that we have at the present! I studied and obtained a PhD at the University of Tokyo, Japan in 2002, and was a postdoctoral researcher at the Max-Planck Institute of Astrophysics, Munich, Germany and later at the Australian National University, Canberra, Australia. I moved to the UK in 2011 to take up a Faculty position at the University of Hertfordshire. I am leading the UK nuclear astrophysics research network BRIDGCE (bridgce.ac.uk). We now have good understanding on the origin of most of stable elements from hydrogen to uranium, but there are a few elements that we can’t explain the observations, including my favourite element, gold!