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Observing the Unobservable: Tracing Dark Matter Haloes and Galaxy Assembly

Speaker(s) / Presenter(s):
Genevieve Graves (Princeton University)
A fundamental challenge in cosmology and galaxy evolution is to understand how dark matter (DM) haloes influence the galaxies that form inside them.  Unfortunately, the parts of this process that we can simulate well --- the growth of DM structures under the influence of gravity --- cannot be observed directly, while the observable stars and gas are difficult to simulate over large scales because of the complicated physics involved.  My past research has focused on connecting the star formation histories of passive galaxies to their observed dynamical structure.  Here, I will present two projects that tackle different aspects of the larger problem of galaxy evolution.  The first is a new method for measuring weak gravitational lensing.  This method uses a photometry-only analog to the Fundamental Plane of early type galaxies in order to measure magnification due to weak lensing.  Combined with existing techniques based on gravitational shear, this method will produce the most direct measurements of dark matter haloes around ordinary galaxies, allowing us to connect observed galaxies with the dark matter haloes that host them.  The second project uses detailed, resolved galaxy kinematics and stellar population gradients in local massive galaxies to trace their assembly history.  The goal is to isolate contributions from in situ star formation, major versus minor mergers, and the possible large-scale stripping of globular clusters.  I will present a pilot study of M87, which is the first of several dozen local galaxies we ultimately aim to analyze.