Speaker
Description
Clusters of galaxies are massive bound systems. At a large radius of 5 Mpc or more, massive clusters of galaxies decouple from the Hubble flow. Within this turnaround radius, galaxies are still accreting onto the cluster in the outer portion, the infall region. In the dense central regions with radii < 2 Mpc, clusters are dynamically relaxed. We use the radial velocity profile of cluster member galaxies from IllustrisTNG to derive two new dynamically determined radii that mark the transition from the region where galaxies are infalling to the inner virialized region. Both of these dynamical radii lie within $1\sigma$ of the splashback radius, the first apocenter of newly accreted galaxies. The dynamically determined radii provide a complementary physical view of the splashback radius as the inner boundary of the infall region.
