TAP Colloquium: Dr. Rachel Somerville
On the Physical Origin of Galaxy Size and Spin
Dr. Rachel Somerville
Downsbrough Chair in Astrophysics
Galaxies famously follow regular scaling relations between their global properties (luminosity or stellar mass) and structural (size, surface brightness) and kinematic (rotation velocity, velocity dispersion) properties. Observations of these scaling relations for different types of galaxies, and their evolution over cosmic time, hold great promise for providing us with insights into the physical processes that shape galaxy formation. I will give an overview of what we have learned about galaxy structural properties and their evolution from recent surveys such as CANDELS. I will then present insights into the physical origin of these structural scaling relations from abundance matching, semi-analytic models, and numerical hydrodynamic simulations. I will argue that the classical paradigm, in which galaxy size is tightly correlated with the angular momentum (spin) of the host dark matter halo, may need to be significantly revised. I will discuss how these insights may help us to test and refine the "sub-grid" recipes that are implemented in cosmological hydrodynamic simulations of galaxy formation.