Simulated star formation rate functions at z~4-7, and the role of
  feedback in high-z galaxies
  We study the role of feedback from supernovae and black holes in the
evolution of the star formation rate function (SFRF) of z~4-7 galaxies. We use
a new set of cosmological hydrodynamic simulations, ANGUS (AustraliaN GADGET-3
early Universe Simulations), run with a modified and improved version of the
parallel TreePM-smoothed particle hydrodynamics code GADGET-3 called
P-GADGET3(XXL), that includes a self-consistent implementation of stellar
evolution and metal enrichment. In our simulations both Supernova (SN) driven
galactic winds and Active Galactic Nuclei (AGN) act simultaneously in a complex
interplay. The SFRF is insensitive to feedback prescription at z>5, meaning
that it cannot be used to discriminate between feedback models during
reionisation. However, the SFRF is sensitive to the details of feedback
prescription at lower redshift. By exploring different SN driven wind
velocities and regimes for the AGN feedback, we find that the key factor for
reproducing the observed SFRFs is a combination of "strong" SN winds and early
AGN feedback in low mass galaxies. Conversely, we show that the choice of
initial mass function and inclusion of metal cooling have less impact on the
evolution of the SFRF. When variable winds are considered, we find that a
non-aggressive wind scaling is needed to reproduce the SFRFs at z>4. Otherwise,
the amount of objects with low SFRs is greatly suppressed and at the same time
winds are not effective enough in the most massive systems.
