Simulating galactic dust grain evolution on a moving mesh
  Interstellar dust is an important component of the galactic ecosystem,
playing a key role in multiple galaxy formation processes. We present a novel
numerical framework for the dynamics and size evolution of dust grains
implemented in the moving-mesh hydrodynamics code AREPO suited for cosmological
galaxy formation simulations. We employ a particle-based method for dust
subject to dynamical forces including drag and gravity. The drag force is
implemented using a second-order semi-implicit integrator and validated using
several dust-hydrodynamical test problems. Each dust particle has a grain size
distribution, describing the local abundance of grains of different sizes. The
grain size distribution is discretised with a second-order piecewise linear
method and evolves in time according to various dust physical processes,
including accretion, sputtering, shattering, and coagulation. We present a
novel scheme for stochastically forming dust during stellar evolution and new
methods for sub-cycling of dust physics time-steps. Using this model, we
simulate an isolated disc galaxy to study the impact of dust physical processes
that shape the interstellar grain size distribution. We demonstrate, for
example, how dust shattering shifts the grain size distribution to smaller
sizes resulting in a significant rise of radiation extinction from optical to
near-ultraviolet wavelengths. Our framework for simulating dust and gas
mixtures can readily be extended to account for other dynamical processes
relevant in galaxy formation, like magnetohydrodynamics, radiation pressure,
and thermo-chemical processes.
