12) Galaxy disks in cosmological dark matter halos

Abstract: Cosmological hydrodynamical simulations are an important tool that can be used to disentangle the relative importance of physical processes giving rise to the broad range of galaxy properties in observational surveys. High fidelity observations of individual stellar tracers in the Milky Way and nearby disk galaxies demand accurate and realistic theoretical models to aid their interpretation. Realistic thin stellar disks have been traditionally difficult to simulate, and remain a problematic case for large cosmological simulations, such as Eagle and Illustris, in which individual "stellar particle" masses are comparable to open or globular clusters in the Milk Way. This discrepancy between the "resolution" of modern observations and simulations will lead to (potentially insurmountable) challenges if care is not taken to draw appropriate comparisons between the two. For example, very little is know about the impact of stellar-particle mass resolution on the structure and kinematics of disks in simulations -- this is potentially detrimental to the interpretation of observations. I will discuss theoretical work that targets these issues, and clarify the important role played by numerical artifact in establishing the kinematics and structure of galaxy disks in simulations. I will outline why recent attempts to artificially increase the baryonic mass resolution in simulations are doomed to fail, and may even exacerbate the underlying problems they attempt to solve.