17) Uncovering past galaxy mergers via population-dynamics of their stars

Abstract: Driven by gravity, galaxies continuously grow through accretion of smaller systems. Stellar streams are nice illustrations of this hierarchical build-up, but the accreted stars quickly disperse. I will present advanced dynamical models that can convert the observed positions and velocities of stars to phase-space quantities like energy and angular momentum which remain largely conserved. In addition, these models can include the observed ages and chemical properties of stars which are also conserved. The resulting population-dynamical models allow us then to uncover even those accretion events which are now fully dispersed.
In this talk, I will focus on our recent discovery of an ancient massive merger in the Fornax lenticular galaxy NGC1380. By the end, I aim to have demonstrated that these models provide a unique bridge between the studies of resolved stars in the Milky Way and integrated-light of high(er)-redshift galaxies. Together with direct coupling to state-of-the-art galaxy formation simulations, these population-dynamical models enable us to uncover the hierarchical build-up of galaxies in a cosmological context.

Bio: I am Full Professor of Theoretical Extragalactic Astrophysics in the Department of Astrophysics at the University of Vienna. My research group (https://www.univie.ac.at/dynamics/) has the expertise and is developing machinery like the DYNAMITE code to construct detailed dynamical models of globular clusters and nearby galaxies. This enables us to infer the luminous and dark matter distribution of these stellar systems, as well as to uncover their formation history.