Supernova feedback in numerical simulations of galaxy formation:
  separating physics from numerics
  While feedback from massive stars exploding as supernovae (SNe) is thought to
be one of the key ingredients regulating galaxy formation, theoretically it is
still unclear how the available energy couples to the interstellar medium and
how galactic scale outflows are launched. We present a novel implementation of
six sub-grid SN feedback schemes in the moving-mesh code Arepo, including
injections of thermal and/or kinetic energy, two parametrizations of delayed
cooling feedback and a `mechanical' feedback scheme that injects the correct
amount of momentum depending on the relevant scale of the SN remnant resolved.
All schemes make use of individually time-resolved SN events. Adopting isolated
disk galaxy setups at different resolutions, with the highest resolution runs
reasonably resolving the Sedov-Taylor phase of the SN, we aim to find a
physically motivated scheme with as few tunable parameters as possible. As
expected, simple injections of energy overcool at all but the highest
resolution. Our delayed cooling schemes result in overstrong feedback,
destroying the disk. The mechanical feedback scheme is efficient at suppressing
star formation, agrees well with the Kennicutt-Schmidt relation and leads to
converged star formation rates and galaxy morphologies with increasing
resolution without fine tuning any parameters. However, we find it difficult to
produce outflows with high enough mass loading factors at all but the highest
resolution, indicating either that we have oversimplified the evolution of
unresolved SN remnants, require other stellar feedback processes to be
included, require a better star formation prescription or most likely some
combination of these issues.
